|
|
Use the commands in this chapter to configure Link Access Procedure Balanced (LAPB), X.25, DDN X.25, and Blacker Front-end Encryption (BFE). X.25 provides remote terminal access; routing using the IP, DECnet, XNS, ISO CLNS, AppleTalk, Novell IPX, Banyan VINES, and Apollo Domain protocols; and bridging.
For X.25 and LAPB configuration information and examples, refer to the "Configuring X.25 and LAPB Commands" chapter of the Router Products Configuration Guide.
Use the bfe EXEC command to allow the router to participate in emergency mode or to end participation in emergency mode when the interface is configured for x25 bfe-emergency decision and x25 bfe-decision ask.
bfe {enter | leave} interface-type numberEXEC
The following example illustrates how to enable an interface to participate in BFE emergency mode:
router# bfe enter interface serial 0
encapsulation bfex25
x25 bfe-decision
x25 bfe-emergency
Use the clear x25-vc privileged EXEC command to clear switched virtual circuits (SVCs) and to reset permanent virtual circuits (PVCs). This command without any arguments clears all X.25 virtual circuits at once by RESTARTing the packet layer service.
clear x25-vc [interface-type] [number] [lcn]| interface-type | The interface name. |
| number | The interface unit number. |
| lcn | (Optional.) A virtual circuit. |
Privileged EXEC
The following example illustrates how to clear all VCs on an interface:
router# clear x25-vc serial 1
x25 idle
Use the cmns enable interface configuration command to enable Connection-Mode Network Service (CMNS) on a nonserial interface. Use the no cmns enable command to disable this capability.
cmns enableThis command has no arguments or keywords.
The CMNS protocol is implicitly enabled whenever an X.25 encapsulation command is included with a serial interface configuration. A particular nonserial interface, however, must be explicitly configured to use CMNS
Interface configuration
After processing this command on the LAN interfaces (Ethernet, FDDI, and Token Ring), all the X.25-related interface configuration commands are made available.
The following example illustrates how to enable CMNS on interface Ethernet 0:
interface ethernet 0
cmns enable
x25 map cmns
Use the encapsulation bfex25 interface configuration command to configure BFE encapsulation on a router attached to a BFE device.
encapsulation bfex25This command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose an X.25 encapsulation method.
Interface configuration
This encapsulation operates to map between Class A IP addresses and the type of X.121 addresses expected by the BFE encryption device.
The following example sets BFE encapsulation on interface serial 0:
interface serial 0
encapsulation bfex25
bfe
x25 remote-red
A router using DDN X.25 Standard Service can act as either a DTE or a DCE device. Use the encapsulation ddnx25 interface configuration command to set DTE DDN X.25 operation.
encapsulation ddnx25This command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose an X.25 encapsulation method.
Interface configuration
This encapsulation operates to map between IP addresses and X.121 addresses used by the Defense Data Network.
The following example sets DTE DDN X.25 operation on interface serial 0:
interface serial 0
encapsulation ddnx25
A router using DDN X.25 Standard Service can act as either a DTE or a DCE device. Use the encapsulation ddnx25-dce interface configuration command to set DCE DDN X.25 operation.
encapsulation ddnx25-dceThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose an X.25 encapsulation method.
Interface configuration
This encapsulation operates to map between IP addresses and X.121 addresses used by the Defense Data Network.
The following example sets DCE DDN X.25 operation on interface serial 0:
interface serial 0
encapsulation ddnx25-dce
Use the encapsulation lapb interface configuration command to exchange datagrams over a serial interface using LAPB encapsulation and operating as the DTE. One end of the link must be DTE and the other end must be DCE.
encapsulation lapbThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose a LAPB encapsulation method.
Interface configuration
The following example sets LAPB DTE encapsulation on interface serial 3:
interface serial 3
encapsulation lapb
lapb protocol
Use the encapsulation lapb-dce interface configuration command to exchange datagrams over a serial interface using LAPB encapsulation and operating as the DCE. One end of the link must be DTE and the other end must be DCE.
encapsulation lapb-dceThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose a LAPB encapsulation method.
Interface configuration
The following example sets LAPB DCE encapsulation on interface serial 3:
interface serial 3
encapsulation lapb-dce
lapb protocol
For DTE operation, use the encapsulation multi-lapb interface configuration command to use multiple local-area network (LAN) protocols on the same line at the same time.
encapsulation multi-lapbThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose a LAPB encapsulation method.
Interface configuration
With the encapsulation multi-lapb command, you can use multiple protocols such as IP, DECnet, and XNS at the same time. Both ends of the line must use the multi-lapb encapsulation; one end of the link must be DCE and the other end DTE.
The following example illustrates how to allow multiple protocols on a LAPB line operating as the DTE:
interface serial 0
encapsulation multi-lapb
For DCE operation, use the encapsulation multi-lapb-dce interface configuration command to enable use of multiple LAN protocols on the same line at the same time.
encapsulation multi-lapb-dceThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose a LAPB encapsulation method.
Interface configuration
With the encapsulation multi-lapb-dce command, you can use multiple protocols such as IP, DECnet, and XNS at the same time. Both ends of the line must use the multi-lapb encapsulation; one end of the link must be DCE and the other end DTE.
The following example illustrates how to allow multiple protocols on a LAPB line operating as the DCE:
interface serial 0
encapsulation multi-lapb-dce
A router using X.25 Level 3 can act as a DTE or DCE device. Use the encapsulation x25 interface configuration command to set X.25 DTE operation.
encapsulation x25This command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose an X.25 encapsulation method.
Interface configuration
The following example sets X.25 DTE operation on interface serial 0:
interface serial 0
encapsulation x25
A router using X.25 Level 3 can act as a DTE or DCE device. Use the encapsulation x25-dce interface configuration command to set X.25 DCE operation.
encapsulation x25-dceThis command has no arguments or keywords.
The default serial encapsulation is HDLC. You must choose an X.25 encapsulation method.
Interface configuration
The following example sets X.25 DCE operation on interface serial 0:
interface serial 0
encapsulation x25-dce
Use the ip tcp header-compression interface configuration command to implement TCP header compression. The header compression complies with the IETF RFC 1144 standard. The no ip tcp header-compression command disables this feature.
ip tcp header-compression [passive]| passive | (Optional.) Outgoing packets are compressed only if incoming TCP packets on the virtual circuit (VC) for a TCP header compression map are compressed. When the passive option is not set, all compressible traffic intended for the TCP header compression address map is compressed. |
Disabled
Interface configuration
The implementation of compressed TCP over X.25 uses a single VC to pass the compressed packets distinct from any VCs used for noncompressed packets.
The header compression increases the speed of interactive TCP/IP sessions over serial lines running at 56/64 kilobits per second or slower by caching the 20 bytes or so of the constant part of the IP packet header.
The following example allows TCP header compression on interface serial 4:
interface serial 4
ip address 131.108.2.1 255.255.255.0
ip tcp header compression
x25 map compressedtcp 131.08.2.5 000000010300 broadcast
x25 map compressedtcp
Use the lapb hold-queue interface configuration command to define the number of frames that can be held while LAPB is unable to send. Use the no lapb hold-queue command without an argument to remove this command from the configuration file and return to the default value.
lapb hold-queue queue-size| queue-size | Defines the number of frames. A hold queue limit of 0 allows an unlimited number of frames in the hold queue. This argument is optional in the no form of the command. |
10 frames for LAPB encapsulation; X25 encapsulation may not set this parameter because proper operation requires that LAPB send all requested frames.
Interface configuration
The following example illustrates how to set the LAPB hold queue limit to allow up to 25 frames:
interface serial 0
lapb hold-queue 25
Use the lapb k interface configuration command to specify the maximum permissible number of outstanding frames, called the window size.
lapb k window-size| window-size | A frame count from 1 to 7. |
7 frames
Interface configuration
The following example changes the LAPB window size (the k parameter) to three packets:
interface serial 0
lapb k 3
Use the lapb n1 interface configuration command to specify the maximum number of bits a frame can hold (the LAPB N1 parameter).
lapb n1 bits| bits | Number of bits from 1088 through 32,832; it must be a multiple of eight. |
12056 bits (1507 bytes total, or 1503 bytes of user information)
Interface configuration
It is not necessary to set N1 to an exact value to support a particular X.25 data packet size, although both ends of a connection should have the same N1 value. The N1 parameter serves to avoid processing of any huge frames that result from a "jabbering" interface, an unlikely event.
The Cisco N1 default value corresponds to the hardware interface buffer size. Any changes to this value must allow for an X.25 data packet and LAPB frame overhead.The software supports an X.25 data packet with a maximum packet size plus 3 or 4 bytes of overhead for modulo 8 or 128 operation, respectively, and LAPB frame overhead of 2 bytes of header for modulo 8 operation plus 2 bytes of CRC.
In addition, the various standards bodies specify that N1 be given in bits rather than bytes. While some equipment can be configured using bytes or by automatically adjusting for some of the overhead information present, Cisco devices are configured using the true value of N1.
Table 1-1 specifies the minimum N1 values needed to support a given X.25 data packet. Note that N1 cannot be set to a value less than what is required to support an X.25 data packet size of 128 bytes under modulo 128 operation. This is because all X.25 implementations must be able to support
128-byte data packets.
| Maximum data in X.25 packet | Minimum N1 value for X.25 modulo 8 | Minimum N1 value for X.25 modulo 8 |
|---|---|---|
| 128 | 1088 | 1088 |
| 256 | 2104 | 2112 |
| 512 | 4152 | 4160 |
| 1024 | 8248 | 8256 |
| 2048 | 16440 | 16448 |
| 4096 | 32824 | 32832 |
Configuring N1 to be less than 2104 will generate a warning message that X.25 may have problems because some nondata packets can use up to 259 bytes.
The N1 parameter cannot be set to a value larger than the default without first increasing the hardware maximum transmission unit (MTU) size.
The X.25 software will accept default packet sizes and CALLs that specify maximum packet sizes greater than what the LAPB layer will support, but will negotiate the CALLs placed on the interface to the largest value that can be supported. For switched CALLs, the packet size negotiation takes place end-to-end through the Cisco router so the CALL will not have a maximum packet size that exceeds the capability of either of the two interfaces involved.
The following example sets the N1 bits to 9600:
interface serial 0
lapb n1 9600
Use the lapb n2 interface configuration command to specify the maximum number of times a data frame can be transmitted (the LAPB N2 parameter).
lapb n2 tries| tries | Transmission count from 1 through 255. |
20 transmissions
Interface configuration
The following example sets the N2 retries to 50:
interface serial 0
lapb n2 50
Use the lapb protocol interface configuration command to configure the protocol carried on the LAPB line.
lapb protocol protocol| protocol | Protocol choice: ip, xns, decnet, appletalk, vines, clns (ISO CLNS), ipx (Novell IPX), and apollo. |
IP; this command is not available when using a multiprotocol LAPB encapsulation.
Interface configuration
This command is valid only if encapsulation commands are set first.
The following example sets AppleTalk as the protocol on the LAPB line:
interface serial 1
lapb protocol appletalk
encapsulation lapb
encapsulation lapb-dce
Use the lapb t1 interface configuration command to set the retransmission timer period (the LAPB T1 parameter).
lapb t1 milliseconds| milliseconds | Number of milliseconds from 1 through 64,000. |
3000 milliseconds
Interface configuration
The retransmission timer determines how long a transmitted frame can remain unacknowledged before the LAPB software polls for an acknowledgment. The design of the LAPB protocol specifies that a frame is presumed to be lost if it is not acknowledged within T1; a T1 value that is too small may result in duplicated control information, which can severely disrupt service.
To determine an optimal value for the retransmission timer, use the privileged EXEC command ping to measure the round-trip time of a maximum-sized frame on the link. Multiply this time by a safety factor that takes into account the speed of the link, the link quality, and the distance. A typical safety factor is 1.5. Choosing a larger safety factor can result in slower data transfer if the line is noisy. However, this disadvantage is minor compared to the excessive retransmissions and effective bandwidth reduction caused by a timer setting that is too small.
The following example sets the T1 retransmission timer to 20,000 milliseconds:
interface serial 0
lapb t1 20000
Use the show cmns EXEC command to display information pertaining to CMNS traffic activity. In particular, you can use this command to display X.25 Level 3 parameters for LAN interfaces (such as Ethernet or Token Ring).
show cmns [interface-name]| interface-name | (Optional.) The interface to describe. |
EXEC
The following is sample output from the show cmns command for an Ethernet interface:
router# show cmns
Ethernet1 is administratively down, line protocol is down
Hardware address is 0000.0c02.5f4c, (bia 0000.0c2.5f4c), state R1
Modulo 8, idle 0, timer 0, nvc 1
Window size: input 2, output 2, Packet size: input 128, output 128
Timer: TH 0
Channels: Incoming-only none, Two-way 1-4095, Outgoing-only none
RESTARTs 0/0 CALLs 0+0/0+0/0+0 DIAGs 0/0
Table 1-2 describes significant fields shown in the display.
show interfaces serial
Use the show interfaces serial EXEC command to display information about a serial interface.
show interfaces serial number| number | Specifies the interface port number. |
EXEC
The following is a partial sample output from the show interfaces serial command for a serial interface using LAPB encapsulation:
router# show interfaces serial 1
LAPB state is SABMSENT, T1 3000, N1 12056, N2 20, K7,
VS 0, VR 0, RCNT 0, Remote VR 0, Retransmissions 2
IFRAMEs 0/0 RNRs 0/0 REJs 0/0 SABMs 3/0 FRMRs 0/0 DISCs 0/0
LAPB state is DISCONNECT, T1 3000, N1 12000, N2 20, K7, TH 3000
Window is closed
IFRAMEs 12/28 RNRs 0/1 REJs 13/1 SABMs 1/13 FRMRs 3/0 DISCs 0/11
Table 1-3 shows the fields relevant to all LAPB connections.
| Parameter | Description |
|---|---|
| LAPB state is | State of the LAPB protocol. |
| T1 3000, N1 12056, ... | Current parameter settings. |
| VS | Modulo 8 frame number of the next outgoing I-frame. |
| VR | Modulo 8 frame number to give to the next I-frame expected to be received. |
| RCNT | Number of received I-frames that have not yet been acknowledged. |
| Remote VR | Number of the next I-frame the remote expects to receive. |
| Retransmissions | Count of I-frames that have been retransmitted. |
| Window is closed | No more frames can be transmitted until some outstanding frames have been acknowledged. |
| IFRAMEs | Count of Information frames in the form of sent/received. |
| RNRs | Count of Receiver Not Ready frames in the form of sent/received. |
| REJs | Count of Reject frames in the form of sent/received. |
| SABMs | Count of Set Asynchronous Balanced Mode commands in the form of sent/received. |
| FRMRs | Count of Frame Reject frames in the form of sent/received. |
| DISCs | Count of Disconnect commands in the form of sent/received. |
The following is a partial sample output from the show interfaces command for a serial X.25 interface:
router# show interfaces serial 1
X25 address 000000010100, state R1, modulo 8, idle 0, timer 0, nvc 1
Window size: input 2, output 2, Packet size: input 128, output 128
Timers: T20 180, T21 200, T22 180, T23 180, TH 0
Channels: Incoming-only none, Two-way 1-1024, Outgoing-only none
(configuration on RESTART: modulo 8,
Window size: input 2 output 2, Packet size: input 128, output 128
Channels: Incoming-only none, Two-way 5-1024, Outgoing-only none)
RESTARTs 3/2 CALLs 1000+2/1294+190/0+0/ DIAGs 0/0
The stability of the X.25 protocol requires that some parameters not be changed without a RESTART of the protocol. Any change to these parameters will be held until a RESTART is sent or received. If any of these parameters will change, the configuration on RESTART information will be output as well as the values that are currently in effect.
Table 1-4 describes significant fields shown in the display.
| Field | Description |
|---|---|
| X25 address 000000010100 | Address used to originate and accept calls. |
| state R1 | State of the interface. Possible values are:
If the state is R2 or R3, the interface is awaiting acknowledgment of a Restart packet. |
| modulo 8 | Modulo value; determines the packet sequence numbering scheme used. |
| idle 0 | Number of minutes the router waits before closing idle virtual circuits that it originated or accepted. |
| timer 0 | Value of the interface timer, which is zero unless the interface state is R2 or R3. |
| nvc 1 | Default maximum number of simultaneous virtual circuits permitted to and from a single host for a particular protocol. |
| Window size: input 2, output 2 | Default window sizes (in packets) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
| Packet size: input 128, output 128 | Default maximum packet sizes (in bytes) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
| Timers: T20 180, T21 200, T22 180, T23 180 | Values of the Request packet timers:
|
|
TH0 | Packet acknowledgment threshold (in packets). This value determines how many packets are received before sending an explicit acknowledgment; the default value (0) sends an explicit acknowledgment only when the incoming window is full. |
| Channels: Incoming-only none Two-way 5-1024 Outgoing-only none | Displays the virtual circuit ranges for this interface. |
| RESTARTs 3/2 | Shows RESTART packet statistics for the interface using the format Sent/Received. |
| CALLs 1000+2/1294+190/0+0 | Shows CALL packet statistics for the interface using these formats:
|
|
DIAGs 0/0 | Shows DIAG packet statistics for the interface using the format Forwarded+Failed forwarded. |
show cmns
Use the show llc2 EXEC command to display active LLC2 connections.
show llc2cThis command has no arguments or keywords.
EXEC
The following is sample output from the show llc2 command:
router# show llc2
TokenRing0 DTE=1000.5A59.04F9,400022224444 SAP=04/04, State=NORMAL
V(S)=5, V(R)=5, Last N(R)=5, Local Window=7, Remote Window=127
ack-max=3, n2=8, Next timer in 7768
xid-retry timer 0/60000 ack timer 0/1000
p timer 0/1000 idle timer 7768/10000
rej timer 0/3200 busy timer 0/9600
ack-delay timer 0/3200
CMNS Connections to:
Address 1000.5A59.04F9 via Ethernet2
Protocol is up
Interface type X25-DCE RESTARTS 0/1
Timers: T10 1 T11 1 T12 1 T13 1
The display includes a CMNS addendum, indicating that LLC2 is running with CMNS. When LLC2 is not running with CMNS, the show llc2 command does not display a CMNS addendum.
Table 1-5 describes significant fields shown in the display.
| Field | Description |
|---|---|
| TokenRing0 | Name of interface on which the session is established. |
| DTE=1000.5A59.04F9, 400022224444 | Address of the station to which the Cisco router is talking on this session. (The router's address is the MAC address of the interface on which the connection is established, except when Local Acknowledgment or SDLLC is used, in which case the address used by the router is shown as in this example, following the DTE address and separated by a comma.) |
| SAP=04/04 | Other station's and router's (remote/local) Service Access Point for this connection. The SAP is analogous to a "port number" on the router and allows for multiple sessions between the same two stations. |
| State= | Current state of the LLC2 session which are any of the following: |
| ADM SETUP RESET D_CONN ERROR AWAIT AWAIT_REJ | Asynchronous Disconnect Mode--A connection is not established, and either end can begin one.
Request to begin a connection has been sent to the remote station, and this station is waiting for a response to that request. A previously open connection has been reset because of some error by this station, and this station is waiting for a response to that reset command. This station has requested a normal, expected, end of communications with the remote, and is waiting for a response to that disconnect request. This station has detected an error in communications and has told the other station about it. This station is waiting for a reply to its posting of this error. Connection between the two sides is fully established, and normal communication is occurring. Normal communication state exists, except busy conditions on this station make it such that this station cannot receive information frames from the other station at this time. Out-of-sequence frame has been detected on this station, and this station has requested that the other resend this information Normal communication exists, but this station has had a timer expire, and is trying to recover from it (usually by resending the frame that started the timer). A combination of the AWAIT and BUSY states. A combination of the AWAIT and REJECT states. |
| V(S)=5 | Sequence number of the next information frame this station will send. |
| V(R)=5 | Sequence number of the next information frame this station expects to receive from the other station. |
| Last N (R)=5 | Last sequence number of this station's transmitted frames acknowledged by the remote station. |
| Local Window=7 | Number of frames this station may send before requiring an acknowledgment from the remote station. |
| Remote Window=127 | Number of frames this station can accept from the remote. |
| ack-max=3, n2=8 | Value of these parameters, as given in the previous configuration section. |
| Next timer in 7768 | Number of milliseconds before the next timer, for any reason, goes off. |
| xid-retry timer 0/60000 .... | A series of timer values in the form of next-time/time-between, where "next-time" is the next time, in milliseconds, that the timer will wake, and "time-between" is the time, in milliseconds, between each timer wakeup. A "next-time" of zero indicates that the given timer is not enabled, and will never wake. |
| CMNS Connections to:
Protocol is up Interface type X25-DCE RESTARTS 0/1 Timers: | CMNS addendum when LLC2 is running with the CMNS protocol contains the following:
MAC address of remote station. Up indicates the LLC2 and X.25 protocols are in a state where incoming and outgoing Call Requests can be made on this LLC2 connection. One of the following: X25-DCE, X25-DTE, or X25-DXE (either DTE or DCE). Restarts sent/received on this LLC2 connection. T10, T11, T12, T13 (or T20, T21, T22, T23 for DTE); these are Request packet timers. These are similar in function to X.25 parameters of the same name. |
Use the show x25 map EXEC command to display information about configured address maps.
show x25 mapThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 map command:
router# show x25 map
Serial0: IP 131.108.170.1 1311001 PERMANENT BROADCAST, 2 LCN: 3 4*
Serial0: appletalk 128.1 1311005 PERMANENT
Serial1: BRIDGE 1311006 PERMANENT
The display shows that three virtual circuits have been configured for the router, two for the Serial0 interface, and one for the Serial1 interface.
Table 1-6 describes significant fields shown in the first line of output in the display.
Use the show x25 remote-red EXEC command to display the one-to-one mapping of the host IP addresses and the remote BFE device's IP addresses.
show x25 remote-redThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 remote-red command:
router# show x25 remote-red
Entry REMOTE-RED REMOTE-BLACK INTERFACE
1 21.0.0.3 21.0.0.7 serial3
2 21.0.0.10 21.0.0.6 serial1
3 21.0.0.24 21.0.0.8 serial3
Table 1-7 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Entry | Address mapping entry. |
| REMOTE-RED | Host IP address. |
| REMOTE-BLACK | IP address of the remote BFE device. |
| INTERFACE | Name of interface through which communication with the remote BFE device will take place. |
Use the show x25 route EXEC command to display the X.25 routing table.
show x25 routeThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 route command:
router# show x25 route
Number X.121 CUD Forward To
1 1311001 Serial0, 0 uses
2 1311002 131.108.170.10, 0 uses
3 1311003 00 alias Serial0, 2 uses
Table 1-8 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Number | Number identifying the entry in the X.25 routing table. |
| X.121 address | X.121 address pattern associated with this entry. |
| CUD | Call User Data, if any, that has been configured for this route. |
| Forward To | Router interface or IP address to which the router will forward a CALL destined for the X.121 address pattern in this entry.
This field also includes the number of uses of this route. |
x25 route
Use the show x25 vc EXEC command to display the parameters and statistics of the active X.25 virtual circuit. To examine a particular virtual circuit, add an LCN argument to the show x25 vc command.
show x25 vc [lcn]
| lcn | (Optional.) Logical channel number (LCN). |
EXEC
For PVCs, the syntax of the third and sometimes fourth line(s) of show x25 vc output varies depending on whether the PVC is in a connected or disconnected state, and whether the connection is locally switched, or remotely tunneled over a TCP connection.
If the PVC is locally switched and connected, the syntax for the third line of output follows:
Switched PVC to interface name PVC #, connected
If the PVC is locally switched and not connected, the syntax for the third line of output follows:
Switched PVC to interface name PVC #, not connected, PVC state string
If the PVC is remotely tunneled and connected, the syntax for the third and fourth lines of output follows:
Tunneled PVC to ip address interface name PVC #, connected
via TCP connection from ip address, port to ip address, port, D-bit allowed
If the PVC is remotely tunneled and not connected, the syntax for the third line of output follows:
Tunneled PVC to ip address interface name PVC #, not connected, PVC state string
The PVC state string represents the state of a PVC. Some of these strings only apply to PVCs that are remotely tunneled over a TCP connection. The %X25-3-PVCBAD system error message (as documented in the System Error Messages publication), and the debug x25 all command (as documented in the Debug Command Reference publication) also use these PVC state strings. These PVC state strings follow:
awaiting PVC-SETUP reply
can't support flow control values
connected
dest. disconnected
dest. interface is not up
dest. PVC configuration mismatch
mismatched flow control values
no such dest. interface
no such dest. PVC
non-X.25 dest. interface
PVC setup protocol error
PVC/TCP connect timed out
PVC/TCP connection refused
PVC/TCP routing error
trying to connect via TCP
waiting to connect
The following is sample output from show x25 vc command for an SVC that carries encapsulated IP diagrams:
router# show x25 vc
LC1: 1, State: D1, Interface: Serial0
Started 0:55:03, last input 0:54:56, output 0:54:56
Connected to IP [10.4.0.32] <->000000320400 Precedent: 0
Window size input: 7, output: 7
Packet size input: 1024, output: 1024
PS: 2 PR: 6 Remote PR: 2 RCNT: 1 RNR: FALSE
Window is closed
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 1111/588 Packets 18/22 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 1-9 describes significant fields shown in the output.
| Field | Description |
|---|---|
| LCI | Virtual circuit number. |
| State | State of the virtual circuit (which is independent of the states of other virtual circuits); D1 is the normal ready state. (See the CCITT X.25 Recommendation for a description of virtual circuit states.) |
| Interface | Interface on which the virtual circuit is established. |
| Started | Time elapsed since the virtual circuit was created. |
| last input | Time of last input. |
| output | Shows time of last output. |
| Connected to | Network-protocol address, in brackets, and the X.121 address of the machine to which the router is locally connected. |
| Precedent | IP precedence (appears only if you have specified DDN encapsulation). |
| Window size | Window sizes for the virtual circuit. |
| Packet size | Maximum packet sizes for the virtual circuit. |
| PS | Current send sequence number. |
| PR | Current receive sequence number. |
| Remote | Last PR number received from the other end of the circuit. |
| RCNT | Count of unacknowledged input packets. |
| RNR | State of the Receiver Not Ready flag; this field is true if the network sends a receiver-not-ready packet. |
| Window is closed | Router cannot transmit any more packets until the remote end has acknowledged some outstanding packets. |
| Retransmits | Number of times a supervisory packet (RESET or CLEAR) has been retransmitted. |
| Timer | A nonzero time value if a packet has not been acknowledged or if virtual circuits are being timed for inactivity. |
| Reassembly | Number of bytes received for a partial packet (a packet in which the more data bit is set). |
| Held Fragments/Packets | Number of X.25 packets being held. (In this case, Fragments refers to the X.25 fragmentation of higher-level data packets.) |
| Bytes | Total number of bytes sent and received. The Packets, Resets, RNRs, REJs, and INTs fields show the total sent and received packet counts of the indicated types. (RNR is Receiver Not Ready, REJ is Reject, and INT is Interrupt). |
When the protocol type used for the connection is CMNS, the display generated with show x25 vc differs slightly from the display outlined in the preceding description.
The following is sample output from the show x25 vc command for two complementary interfaces, both running CMNS, and transmitting CMNS traffic to each other:
router# show x25 vc
LCI: 1, State: P4, Interface: Serial1
Started 0:23:00, last input never, output never
Connected to CMNS [37.1111] <--> 313131 via Ethernet1 LCN 4095 to 0000.0c01.487d
Window size input: 6, output: 6
Packet size input: 1024, output: 1024
PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
--More--
LCI: 4095, State: P4, Interface: Ethernet1
Started 0:23:01, last input never, output never
Connected to CMNS [36.3030.3030.3030.30] <--> 0000.0c01.487d
via Serial1 LCN 1to 313131
Window size input: 6, output: 6
Packet size input: 1024, output: 1024
PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0\
Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 1-10 describes significant fields shown in the display.
| Field | Description |
|---|---|
| LCI | Virtual circuit number; range is 1 through 4095. |
| State | State of the virtual circuit (which is independent of the states of other virtual circuits); P4 indicates the interface is in the data transfer state (See the CCITT X.25 recommendation for a description of virtual circuit states.) |
| Interface | Interface used for the virtual circuit. With CMNS, this can indicate Ethernet, Token Ring, and FDDI interfaces, as well as Serial. |
| Connected to Ethernet1 | NSAP address, in brackets, for the device at the indicated X.121 address. Logical Channel Number (LCN) used (1 through 4095) and the MAC address of the node to which the interface is connected. |
Use the x25 accept-reverse interface configuration command to instruct the router to accept all reverse charge calls. The no x25 accept-reverse command disables this facility.
x25 accept-reverseThis command has no arguments or keywords.
Disabled
Interface configuration
This command causes the interface to accept reverse charge calls by default. This behavior also can be configured on a per-peer basis using the x25 map interface configuration command.
The following example illustrates how to set acceptance of reverse charge calls:
interface serial 0
x25 accept-reverse
x25 map
Use the x25 address interface configuration command to set the X.121 address of a particular network interface.
x25 address X.121-address| X.121-address | Variable-length X.121 address. The address is assigned by the X.25 network service provider. |
DDN and BFE encapsulations have a default interface address generated from the interface IP address. Standard X.25 encapsulations do not have a default
Interface configuration
The following example sets the X.121 address for the interface:
interface serial 0
x25 address 00000123005
The address must match that assigned by the X.25 network service provider.
Use the x25 bfe-decision interface configuration command to direct how a router configured for x25 bfe-emergency decision will participate in emergency mode.
x25 bfe-decision {no | yes | ask}| no | Prevents the router from participating in emergency mode and from sending address translation information to the BFE device. |
| yes | Allows the router to participate in emergency mode and to send address translation information to the BFE when the BFE enters emergency mode. The router obtains this information from the table created by the x25 remote-red command. |
| ask | Configures the router to display an onscreen request to enter the bfe EXEC command. |
no
Interface configuration
The following example shows how to configure interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0
x25 bfe-emergency decision
x25 remote-red 21.0.0.12 remote-black 21.0.0.1
x25 bfe-decision ask
bfe
x25 bfe-emergency
x25 remote-red
Use the x25 bfe-emergency interface configuration command to configure the circumstances under which the router participates in emergency mode.
x25 bfe-emergency {never | always | decision}never
Interface configuration
The following example shows how to configure interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0
x25 bfe-emergency decision
x25 remote-red 21.0.0.12 remote-black 21.0.0.1
x25 bfe-decision ask
bfe
x25 bfe-decision
Use the x25 default interface configuration command to set a default protocol. Use the no x25 default command to remove the protocol specified.
x25 default protocol| protocol | Specifies the protocol; can only be IP, specified by the ip keyword. |
None
Interface configuration
This command specifies the protocol assumed by the router to interpret incoming calls with unknown Call User Data. If you do not use the x25 default interface configuration command, the router clears any incoming calls with unknown Call User Data.
The following example illustrates how to establish IP as the default protocol for X.25 calls:
interface serial 0
x25 default IP
x25 map
Use the x25 facility interface configuration command to force facilities on a per-call basis for calls originated by the router. Use the no x25 facility command to disable a facility.
x25 facility facility-keyword value| facility-keyword | User facility. |
| value | Facility value; see Table 1-11 for a list of supported facilities and their values. |
No facility sent
Interface configuration
The following example illustrates how to specify a transit delay value in an X.25 configuration:
interface serial 0
x25 facility transit-delay 24000
The following example illustrates how to set an RPOA name and then send the list via the X.25 user facilities:
x25 rpoa green_list 23 35 36
interface serial 0
x25 facility rpoa green_list
x25 rpoa
Use the x25 hic interface configuration command to set the highest incoming-only virtual circuit number.
x25 hic circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an incoming only virtual circuit range. Incoming is from the perspective of the X.25 DTE. If you do not want any outgoing calls from your DTE, configure both ends to disable the two-way range (set tc and htc to 0) and configure an incoming-only range. Any incoming-only range must come before (that is, must be numerically less than) any two-way range. Any two-way range must come before any outgoing-only range.
The following example illustrates how to set a valid incoming-only virtual circuit range of 1 to 5:
interface serial 0
x25 lic 1
x25 hic 5
x25 ltc 6
x25 lic
Use the x25 hoc interface configuration command to set the highest outgoing-only virtual circuit number.
x25 hoc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set tc and htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
The following example illustrates how to set a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0
x25 loc 2000
x25 hoc 2005
x25 loc
Use the x25 hold-queue interface configuration command to modify the maximum number of packets that can be held until a virtual circuit is able to transmit. Use the no x25 hold-queue command without an argument to remove this command from the configuration file and restore the default value.
x25 hold-queue queue-size| queue-size | Defines the number of packets. A hold queue value of 0 allows an unlimited number of packets in the hold queue. This argument is optional for the no form of this command. |
10 packets
Interface configuration
If you set the queue-size to 0 when using the no x25 hold-queue command, there will be no hold queue limit. While this will prevent drops until the router runs out of memory, it is only rarely appropriate. A virtual circuit hold queue value is determined when it is created; changing this parameter will not affect the hold queue limits of the existing VCs.
The following example illustrates how to set the X.25 hold queue to hold 25 packets:
interface serial 0
x25 hold-queue 25
A dagger (+) indicates that the command is documented in another chapter.
ip mtu +
x25 ips
x25 ops
Use the x25 hold-vc-timer interface configuration command to prevent overruns on some X.25 switches caused by Call Request packets. This command starts the hold-vc-timer to prevent additional calls to a destination for a given period of time. The no x25 hold-vc-timer command restores the default value for the timer.
x25 hold-vc-timer minutes| minutes | Number of minutes to prevent calls from going to a previously failed destination. Incoming calls still will be accepted. |
0
Interface configuration
Only Call Requests that the router originates will be held down; routed X.25 Call Requests are not affected by this parameter.
Upon receiving a Clear Request for an outstanding Call Request, the X.25 support code immediately tries another Call Request if it has more traffic to send, and this action might cause overrun problems.
The failed VC(s) may be observed with the show x25 vc command; they are renumbered to the illegal value 4096 and have the non-standard state X1.
The following example illustrates how to set the hold-vc-timer to 3 minutes:
interface serial 0
x25 hold-vc-timer 3
Use the x25 host global configuration command to define a static host name-to-address mapping. Use the no x25 host command to remove the host name.
x25 host name X.121-address [cud call-user-data]| name | Host name. |
| X.121-address | The X.121 address. |
| cud call-user-data | (Optional.) Specifies the Call User Data (CUD) field in the X.25 Call Request packet. |
None
Global configuration
The following example illustrates how to specify a static address mapping:
x25 host Willard 4085551212
The following example illustrates how to remove a static address mapping:
no x25 host Willard
Use the x25 htc interface configuration command to set the highest two-way virtual circuit number.
x25 htc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. |
1024 for X.25 network service interfaces; 4095 for CMNS network service interfaces.
Interface configuration
This command is applicable if you have the X.25 switch configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example illustrates how to set a valid two-way virtual circuit range of 5 to 25:
interface serial 0
x25 ltc 5
x25 htc 25
cmns enable
x25 ltc
The router can clear a switched virtual circuit (SVC) after a period of inactivity. Use the x25 idle interface configuration command to set this period.
x25 idle minutes| minutes | Number of minutes in the idle period. |
0 (causes the router to keep the SVC open indefinitely)
Interface configuration
Both calls originated and terminated by the router are cleared; switched virtual circuits are not cleared. To clear one or all virtual circuits at once, use the privileged EXEC command clear x25-vc.
The following example illustrates how to set a 5-minute wait period before an idle circuit is cleared:
interface serial 2
x25 idle 5
clear x25-vc
Use the x25 ip-precedence interface configuration command to enable the ability to open a new virtual circuit based on the IP precedence value. The command no x25 ip-precedence causes the precedence value to be ignored when opening virtual circuits.
x25 ip-precedenceThis command has no arguments or keywords.
The routers open one virtual circuit for all types of service.
Interface configuration
There is a problem associated with this feature in that some hosts send nonstandard data in the IP TOS field, thus causing multiple, wasteful virtual circuits to be created.
Four VCs may be opened based on IP precedence to encapsulate routine, priority, immediate, and all higher precedences.
The nvc limit specified for the map or the interface default nvc limit still applies.
Although an originated VC will be restricted to traffic of a particular precedence, VCs that are received and accepted have no precedence associated.
The following example illustrates how to allow new IP encapsulation virtual circuits based on the IP precedence:
interface serial 3
x25 ip-precedence
Use the x25 ips interface configuration command to set the interface default maximum input packet size to match that of the network.
x25 ips bytes| bytes | Byte count that is one of the following: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. |
128 bytes
Interface configuration
X.25 network connections have a default maximum input packet size set by the network administrator. Larger packet sizes require less overhead processing. To send a packet larger than the X.25 packet size over an X.25 virtual circuit, a router must break the packet into two or more X.25 packets with the M-bit ("more data" bit) set. The receiving device collects all packets with the
M-bit set and reassembles them.
The following example shows how to set the default maximum packet sizes to 512:
interface serial 1
x25 ips 512
x25 ops 512
x25 ops
Use the x25 lic interface configuration command to set the lowest incoming-only virtual circuit number.
x25 lic circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set tc and htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
This command is applicable if you have the X.25 switch configured for two way virtual circuit range.
The following example shows how to set a valid incoming-only virtual circuit range of 1 to 5:
interface serial 0
x25 lic 1
x25 hic 5
x25 ltc 6
x25 hic
Use the x25 linkrestart interface configuration command to force a packet-level restart when the link level resets. This command restarts X.25 Level 3 when errors occur in Level 2 (LAPB). The no x25 linkrestart command disables this function.
x25 linkrestartThis command has no arguments or keywords.
Forcing packet-level restarts is the default and is necessary for networks that expect this behavior.
Interface configuration
The following example illustrates how to disable the link level restart:
interface serial 3
no x25 linkrestart
Use the x25 loc interface configuration command to set the lowest outgoing-only virtual circuit number.
x25 loc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for outgoing only. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls from your DTE, configure the loc and hoc values and set the ltc and htc values to 0.
The following example illustrates how to set a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0
x25 loc 2000
x25 hoc 2005
x25 hoc
Use the x25 ltc interface configuration command to set the lowest two-way virtual circuit number.
x25 ltc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. |
1
Interface configuration
This command is applicable if you have the X.25 switch configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example illustrates how to set a valid two-way virtual circuit range of 5 to 25:
interface serial 0
x25 ltc 5
x25 htc 25
x25 htc
Use the x25 map interface configuration command to set up the LAN protocol-to-X.121 address mapping for the host. Because no defined protocol can dynamically determine such mappings, you must enter a mapping for each host with which the router will exchange traffic. Use the no x25 map command with the appropriate network protocol and X.121 address arguments to retract a network protocol-to-X.121 mapping.
x25 map protocol-keyword protocol-address X.121-address [option]| protocol-keyword | Selects the protocol type. Supported protocol keywords are listed in Table 1-12. |
| protocol-address | Specifies the protocol address. |
| X.121-address | Specifies the X.121 address. Both addresses specify the network protocol-to-X.121 mapping. |
| option | (Optional.) Provides additional functionality or the X.25 essential user facilities to the mapping specified. Can be any of the options listed in Table 1-13). |
| Keyword | Protocol |
|---|---|
| ip | IP |
| decnet | DECnet |
| xns | XNS |
| novell | Novell IPX |
| appletalk | AppleTalk |
| vines | VINES |
| apollo | Apollo Domain |
| bridge | Bridging |
| clns | OSI Connectionless Network Service |
| cmns | OSI Connection-Mode Network Service |
| compressedtcp | TCP header compression |
None
Interface configuration
The broadcast keyword simplifies the configuration of OSPF for nonbroadcast networks that will use X.25.
OSPF treats a nonbroadcast, multiaccess network such as X.25 much the same way it treats a broadcast network in that it requires selection of a designated router. In previous releases, this required manual assignment in the OSPF configuration using the neighbor interface router configuration command. When the x25 map command is included in the configuration with the broadcast keyword, there is no need to configure any neighbors manually. OSPF will now automatically run over the Frame Relay network as a broadcast network.
The broadcast keyword directs any broadcasts sent through this interface to the specified X.121 address. The following example illustrates how to map IP address 131.08.2.5 to X.121 address 000000010300:
interface serial 0
x25 map ip 131.08.2.5 000000010300 broadcast
The following example illustrates how to set an RPOA name for use in the connection:
x25 rpoa green_list 23 35 36
interface serial 0
x25 facility rpoa green_list
x25 map ip 131.108.170.26 10 rpoa green_list
The following example shows how to add a network user identifier (NUI) to the address map:
interface serial 0
x25 map IP 131.108.174.32 2 nudata "Network User ID 35"
Strings can be quoted, but quotes are not required unless embedded blanks are present.
x25 map bridge
x25 map cmns
x25 map compressedtcp
Use the x25 map bridge interface configuration command to configure bridging over X.25. The command specifies Internet-to-X.121 address mapping.
x25 map bridge X.121-address broadcast [options-keywords]| X.121-address | The X.121 address. |
| broadcast | Required keyword for bridging X.25 frames. |
| options-keywords | (Optional.) Services that can be added to this map; see Table 1-13 earlier in this chapter for a list of supported services. |
None
Interface configuration
The following example illustrates how to configure bridging of X.25 frames using a maximum of six VCs:
interface serial 1
x25 map bridge 000000010300 broadcast nvc 6
x25 map
Use the x25 map cmns interface configuration command to map NSAP addresses to either MAC-layer addresses or X.121 addresses after enabling CMNS on a nonserial interface. To retract a mapping, use the no x25 map cmns command with the appropriate address arguments.
x25 map cmns nsap mac-address| nsap | NSAP address. The NSAP can be either the actual DTE NSAP address or the prefix of the NSAP address. The NSAP prefix is sufficient for a best match to route a call. |
| mac-address | MAC-level address. |
| X.121-address | (Optional.) X.121 address. |
None
Interface configuration
The address arguments specify the NSAP address-to-MAC address or NSAP address-to-X.121 address mappings. A mapping to a MAC address is only valid on a non-serial interface. A mapping to an X.121 address is only valid on a serial interface.
The following example shows how to switch traffic intended for any NSAP address with prefix 38.8261.17 to MAC address 000.0C02.5F56 over interface Ethernet 0:
interface ethernet 0
cmns enable
x25 map cmns 38.8261.17 000.0C02.5F56.
cmns enable
x25 map
Use the x25 map compressedtcp interface configuration command to map compressed TCP traffic to X.121 addresses. The no x25 map compressedtcp command deletes a TCP header compression map for the link.
x25 map compressedtcp ip-address X.121-address [options]| ip-address | The IP address. |
| X.121-address | The X.121 address. |
| options | (Optional.) The same options as those for the x25 map command described in Table 1-13. |
None
Interface configuration
TCP header compression is supported over X.25 links. The implementation of compressed TCP over X.25 uses a virtual circuit (VC) to pass the compressed packets. The noncompressed packets use separate VCs. The NVC map option cannot be used for TCP header compression, as only one VC can carry compressed TCP header traffic to a given host.
The following example establishes packet compression on interface serial 4:
interface serial 4
ip tcp header-compression
x25 map compressedtcp 131.108.2.5 000000010300
ip tcp header-compression
x25 map
Use the x25 modulo interface configuration command to set the window modulus).
x25 modulo modulus| modulus | Either 8 or 128. The value of the modulo parameter must agree with that of the device on the other end of the X.25 link. |
8
Interface configuration
X.25 supports flow control with a sliding window sequence count. The window counter restarts at zero upon reaching the upper limit, which is called the window modulus. Modulo 128 operation is also referred to as extended packet sequence numbering, which allows larger packet windows.
The following example illustrates how to set the window modulus to 128:
interface serial 0
x25 modulo 128
x25 win
x25 wout
x25 facility windowsize
Use the x25 nvc interface configuration command to specify the maximum number of switched virtual circuits (SVCs) that a protocol can have open simultaneously to one host. To increase throughput across networks, you can establish up to eight switched virtual circuits to a host protocol.
x25 nvc count| count | Circuit count from 1 to 8. A maximum of eight VCs can be configured for each protocol/host pair. Protocols that do not tolerate out-of-order delivery, such as encapsulated TCP header compression, will only use one virtual circuit despite this value. |
1
Interface configuration
When the windows and output queues of all existing connections to a host are full, a new virtual circuit will be opened to the designated circuit count. If a new connection cannot be opened, the data is dropped.
The following example illustrates how to set the default maximum number of switched virtual circuits that can be open simultaneously to 4:
interface serial 0
x25 nvc 4
Use the x25 ops interface configuration command to set the interface default maximum output packet size to match that of the network.
x25 ops bytes| bytes | Byte count that is one of the following: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. |
128 bytes
Interface configuration
X.25 networks use maximum output packet sizes set by the network administration. Larger packet sizes are better because smaller packets require more overhead processing. To send a packet larger than the X.25 packet size over an X.25 virtual circuit, a router must break the packet into two or more X.25 packets with the M-bit ("more data" bit) set. The receiving device collects all packets with the M-bit set and reassembles them.
The following example shows how to set the default maximum packet sizes to 512:
interface serial 1
x25 ips 512
x25 ops 512
x25 ips
Use the encapsulating version of the x25 pvc interface configuration command to establish an encapsulation permanent virtual circuit (PVC). To delete the PVC, use the no x25 pvc command with the appropriate channel number, protocol keyword, and protocol address.
x25 pvc circuit protocol-keyword protocol-address [option]| circuit | Virtual-circuit channel number which must be less than the virtual circuits assigned to the switched virtual circuits (SVCs). |
| protocol-keyword | Protocol type. Supported protocols are listed in Table 1-14. |
| protocol-address | Address of the host at the other end of the PVC. |
| option | (Optional.) PVC's flow control parameters if they differ from the interface defaults. The option arguments add certain features to the mapping specified and can be either of the options listed in Table 1-15. |
| Keyword | Protocol |
|---|---|
| ip | IP |
| decnet | DECnet |
| xns | XNS |
| novell | Novell IPX |
| appletalk | AppleTalk |
| vines | VINES |
| apollo | Apollo Domain |
| bridge | Bridging |
| clns | OSI Connectionless Network Service |
| compressedtcp | TCP header compression |
None; the PVC window and maximum packet sizes default to the map values or the interface default values.
Interface configuration
PVCs are not supported for ISO CMNS.
You must specify the required network protocol-to-X.121 address mapping with an x25 map command before you can set up a PVC.
The following example shows how to establish a PVC on a channel with a VINES host attached:
interface serial 0
x25 map vines 60002A2D:0001 11110001
x25 pvc 2 vines 60002A2D:0001
x25 map
Use the switched version of the x25 pvc interface configuration command to configure a switched permanent virtual circuit (PVC) for a given interface.
x25 pvc pvc-number1 interface interface-name pvc pvc-number2 [option]| pvc-number1 | PVC number that will be used on the local interface (as defined by the primary interface command). |
| interface | Required keyword to specify an interface. |
| interface-name | Remote interface type and unit number (serial 0, for example). |
| pvc | Required keyword to specify a switched PVC. |
| pvc-number2 | Number that will be used on the remote interface. |
| option | (Optional.) Adds certain features to the mapping specified; can be either option listed in Table 1-16. |
None; the PVC window and maximum packet sizes default to the interface default values.
Interface configuration
You can configure X.25 PVCs in the X.25 switching software. This means that DTEs that require permanent circuits can be connected to the router acting as an X.25 switch and have a properly functioning connection. X.25 RESETs will be sent to indicate when the circuit comes up or goes down.
PVC circuit numbers must come before (that is, be numerically smaller than the circuit numbers allocated to any SVC range.
The following example configures a PVC connected between two serial interfaces on the same router. In this type of interconnection configuration, the alternate interface must be specified along with the PVC number on that interface. To make a working PVC connection, two commands must be specified, each pointing to the other as this example illustrates.
interface serial 0
encapsulation x25
x25 ltc 5
x25 pvc 1 interface serial 1 pvc 1
interface serial 1
encapsulation x25
x25 ltc 5
x25 pvc 1 interface serial 0 pvc 1
Use the tunnel version of the x25 pvc interface configuration command to connect two PVCs across a TCP/IP LAN.
x25 pvc pvc-number1 tunnel ip-address interface serial string pvc pvc-number2 [options]
| pvc-number1 | PVC number of the connecting device. |
| tunnel | Indicates two PVCs will be connected across a TCP/IP LAN. |
| ip-address | IP address of the router to which you are connecting. |
| interface serial | Indicates the interface is serial. |
| string | Serial interface specification that accepts either a number or a string in model 7000 format (number/number) to denote the serial interface. |
| pvc | Indicates a PVC. |
| pvc-number2 | Remote PVC number on the target interface. |
| options | (Optional.) Adds certain features for the connection; can be either option listed in Table 1-17. |
None; the PVC window and packet sizes default to the interface default values.
Interface configuration
Use the PVC tunnel commands to tell the router to what the far end of the PVC is connected. The incoming and outgoing packet sizes and window sizes must match the remote PVC outgoing and incoming sizes.
The following example illustrates how to enter the parameters for one side of a connection destined for a router platform other than the model 7000:
interface serial 0
x25 pvc 1 tunnel 131.108.1.2 interface serial 1 pvc 2
The following example illustrates how to enter the parameters for one side of a connection destined for a model 7000:
interface serial 0
x25 pvc 1 tunnel 131.108.1.2 interface serial 1/1 pvc 2
See the section "LAPB and X.25 Configuration Examples" in the Router Products Configuration Guide for more complete configuration examples.
Use the x25 remote-red interface configuration command to set up the table that lists the BFE nodes (host or gateways) to which the router will send packets.
x25 remote-red host-ip-address remote-black blacker-ip-address| host-ip-address | IP address of the host or a router that the packets are being sent to. |
| remote-black | Delimits the addresses for the table being built. |
| blacker-ip-address | IP address of the remote BFE device in front of the host to which the packet is being sent. |
None
Interface configuration
The table that results from this command provides the address translation information the router sends to the BFE when it is in emergency mode.
The following example sets up a short table of BFE nodes for interface serial 0:
interface serial 0
x25 remote-red 131.108.9.3 remote-black 131.108.9.13
x25 remote-red 192.108.15.1 remote-black 192.108.15.26
x25 bfe-decision
show x25 remote-red
Use the x25 route global configuration command to create an entry in the X.25 routing table. Enter the no x25 route command with the appropriate arguments and keywords to remove an entry from the table.
x25 route [# position] X.121-address [cud pattern] interface interface number| # position | (Optional.) A pound sign (#) followed by a number to designate a positional parameter at which to insert the new entry. If no position parameter is given, the entry is appended to the end of the routing table. |
| X.121-address | The called X.121 address pattern. This argument can be either an actual X.121 destination address or a regular expression such as 1111*, representing a group of X.121 addresses. |
| cud pattern | (Optional.) Call User Data pattern which is specified as a printable ASCII string. The Call User Data field may be present in a call packet and is commonly 4 bytes long. |
| interface interface number | Specifies the destination interface (type followed by the unit or port number); for example, interface Ethernet 0. |
| ip ip-address | Specifies an IP address of the network interface or DTE for connections routed through a LAN. Optionally, up to five alternate IP addresses can be listed and each in turn will be tried in the event that the first destination fails, thus allowing alternate routes and decreasing the likelihood of failure. |
| alias interface number | Configures an interface alias. Specify the interface type followed by the unit or port number of the interface. Encapsulation calls are normally accepted when the destination address is that of the interface (or the zero-length X.121 address). Aliases allow the specified interface to accept calls with other destination addresses. |
| substitute-source rewrite-pattern | (Optional.) Specifies the calling X.121 address to replace in locally routed X.25 calls. The backslash (\) character is treated specially in the argument rewrite-pattern; it indicates that the digit immediately following it selects a portion of the original called address to be inserted in the new called address. The characters \0 are replaced with the entire original address. The characters \1 through \9 are replaced with the strings that matched the first through ninth parenthesized parts of X.121-pattern. See Table 1-18 and Table 1-19 for summaries of pattern and character matching, respectively. |
| substitute-dest rewrite-pattern | (Optional.) Specifies the called X.121 address to replace in locally routed X.25 calls. (For backwards compatibility, the substitute keyword will be accepted as substitute-dest and written to nonvolatile memory in the new format.) The backslash (\) character is treated specially in the argument rewrite-pattern; it indicates that the digit immediately following it selects a portion of the original called address to be inserted in the new called address. The characters \0 are replaced with the entire original address. The characters \1 through \9 are replaced with the strings that matched the first through ninth parenthesized parts of X.121-pattern. See Table 1-18 and Table 1-19 for summaries of pattern and character matching, respectively. |
None
Global configuration
The X.25 routing table is consulted when an incoming call is received that should be forwarded to its destination. Two fields are used to determine the route: the called X.121 network interface address (or destination host address), and the X.25 packet's Called User Data (CUD) field. When the destination address and the CUD of the incoming packet fit the X.121 and CUD patterns in the routing table, the call is forwarded.
The order in which X.25 routing table entries are specified is significant; the list is scanned for the first match. The optional argument # position (# followed by a number) designates the line number at which to insert the new router. If no position parameter is given, the entry is appended to the end of the routing table.
The argument X.121-address can be either an actual X.121 destination address or a regular expression such as 1111*, representing a group of X.121 addresses.
The optional Call User Data pattern can be specified as a printable ASCII string. Both the X.121 address and Call User Data can be written using UNIX-style, regular expressions. The Call User Data field is matched against any data in the call, which is commonly 4 bytes long.
X.121 address and Call User Data are used to find a matching routing table entry. The list is scanned from the beginning to the end and each entry is pattern-matched with the incoming X.121 address and Call User Data to the X.121 and Call User Data in the routing table entry. If the pattern match for both entries succeeds, then that route is used. If the incoming call does not have any Call User Data, then only the X.121 address pattern match need succeed with an entry that only contains an X.121 pattern. If Call User Data is present, and while scanning, a route is found that matches the X.121 address but does not have a Call User Data pattern, then that route is used when an exact match cannot be found. Regular expressions are used to allow pattern-matching operations on the X.121 addresses and Call User Data. A common operation is to do prefix matching on the X.121 DNIC field and route accordingly. For example, the pattern ^3306 will match all X.121 addresses with a DNIC of 3306. The caret (^) is a special regular expression character that anchors the match at the beginning of the pattern.
If a matching route is found, the incoming call is forwarded to the next hop depending on the routing entry. If no match is found, the call is cleared. If the route specifies a serial interface running X.25, the router will attempt to forward the call over that interface. If the interface is not operational the remaining routes will be checked for forwarding to an operational interface. If the interface is operational but out of available virtual circuits, the call will be cleared. Otherwise, the expected Clear Request or Call Accepted message will be forwarded back toward the originator. The "null 0" interface can be used as the destination to refuse calls to specific locations. A call cannot be forwarded out the interface it arrived on.
If the matching route specifies an IP address, a TCP connection will be established to port 1998 at the specified IP address, which must be another Cisco router. The Call Request packet will be forwarded to the remote router, where it will be processed in a similar fashion. If a routing table entry is not present or the serial interface is down or out of virtual circuits, a Clear Request will be sent back and the TCP connection will be closed. Otherwise, the call will be forwarded over the serial interface and the expected Clear Request or Call Accepted packet will be returned. Incoming calls received via TCP connections that match a routing entry specifying an IP address will be cleared. This restriction prevents Cisco routers from establishing a TCP connection to another router that would establish yet another TCP connection. A router must always connect to the remote router with the destination DTE directly attached.
See Table 1-18 and Table 1-19 for summaries of pattern and character matching. A more complete description of the pattern-matching characters is found in Appendix C.
Note that address substitution is only performed on routes to an interface. When running X.25 over IP, address substitution can be performed on the destination IP system if the destination system is configured with the appropriate X.25 routing commands.
Use the show x25 route command to display the X.25 routing table. The interface routes will show up after any routes used for translation commands. Because the interface routes are expected to be less specific, they should come last. This is done automatically.
| Pattern | Description |
|---|---|
| \0 | Replaces the entire original address. |
| \1...9 | Replaces strings that match the first through ninth parenthesized part of the X.121 address. |
| * | Matches 0 or more sequences of the regular expressions. |
| + | Matches 1 or more sequences of the regular expressions. |
| ? | Matches the regular expression of the null string. |
| Character | Description |
|---|---|
| ^ | Matches the null string at the beginning of the input string. |
| $ | Matches the null string at the end of the input string. |
| \char | Matches char. |
| . | Matches any single character. |
The following example illustrates how to use regular expression pattern matching characters to match just the initial portion of the complete X.25 address:
x25 route ^3107 interface serial 0
In the following example, if a call comes in on interface serial 0 and matches any X.121-address pattern, the call will be accepted for encapsulating traffic configured for the interface using x25 map commands:
x25 route .* alias serial 0
In the following example, a call will be accepted if destined for either the VAX X.121 address or the address given in the x25 address interface command:
x25 route vax-x121-address alias serial 0
The following example illustrates how to configure alternate IP addresses for the routing table. In the event the first address listed is not available, the next address is tried, and so on until a connection is made:
x25 route ^3106 ip 131.08.2.5 131.08.7.10 131.08.7.9
show x25 route
Use the x25 routing global configuration command to enable X.25 switching or tunneling. The command no x25 routing disables the forwarding of X.25 calls.
x25 routing [USE-TCP-IF-DEFS]| USE-TCP-IF-DEFS | (Optional.) May be used to modify the acceptance of calls received over TCP. |
Disabled
Global configuration
The x25 routing command enables local switching or tunneling, which is used for remote switching to allow routing X.25 traffic through a LAN. X.25 calls will not be forwarded until this command is issued. The USE-TCP-IF-DEFS flag may be needed when receiving remotely routed calls from Cisco routers using older software versions. Normally calls received over a TCP connection (remote routing reception) will have the flow control parameters (window sizes and maximum packet sizes) indicated, because proper operation of routed X.25 requires that these values match at both ends of the connection. Some previous versions of our software, however, do not ensure that these values are present in al calls. In this case the router normally forces universally acceptable flow control values (window sizes of 2 and maximum packet of 128) on the connection. Because some equipment disallows modification of the flow control values in the call confirm, the USE-TCP-IF-DEFS will cause the router to use the default flow control values of the outgoing interface and indicate the resulting values in the call confirm. This modified behavior may allow easier migration to newer versions of the router code.
The following example illustrates how to enable X.25 switching:
x25 routing
Use the x25 rpoa global configuration command to specify a sequence of packet network carriers. The no x25 rpoa command removes the specified name.
x25 rpoa name number| name | Recognized Private Operating Agency (RPOA), which must be unique with respect to all other RPOA names. It is used in the x25 facility and x25 map interface configuration commands. |
| number | A sequence of 1 or more numbers used to describe an RPOA; up to 10 numbers are accepted. |
None
Global configuration
This command specifies a list of transit RPOAs to use, referenced by name.
The following example illustrates how to set an RPOA name and then send the list via the X.25 user facilities:
x25 rpoa green_list 23 35 36
interface serial 0
x25 facility rpoa green_list
x25 map ip 131.108.170.26 10 rpoa green_list
x25 facility
x25 map
Use the x25 suppress-called-address interface configuration command to omit the destination address in outgoing calls. Use the no x25 suppress-called-address command to reset this command to the default state.
x25 suppress-called-addressThis command has no arguments or keywords.
The called address is sent by default.
Interface configuration
This command omits the called (destination) X.121 address in Call Request packets and is required for networks that expect only subaddresses in the called address field.
The following example illustrates how to suppress or omit the called address in Call Request packets:
interface serial 0
x25 suppress-called-address
Use the x25 suppress-calling-address interface configuration command to omit the source address in outgoing calls. Use the no x25 suppress-calling-address command to reset this command to the default state.
x25 suppress-calling-addressThis command has no arguments or keywords.
The calling address is sent by default.
Interface configuration
This command omits the calling (source) X.121 address in Call Request packets and is required for networks that expect only subaddresses in the calling address field.
The following example illustrates how to suppress or omit the calling address in Call Request packets:
interface serial 0
x25 suppress-calling-address
Use the x25 t10 interface configuration command to set the value of the Restart Indication retransmission timer (T10) on DCE devices.
x25 t10 seconds| seconds | Amount of time in seconds. |
60 seconds
Interface configuration
The following example sets the T10 timer to 30 seconds:
interface serial 0
x25 t10 30
Use the x25 t11 interface configuration command to set the value of the Incoming Call timer (T11) on DCE devices.
x25 t11 seconds| seconds | Amount of time in seconds. |
180 seconds
Interface configuration
The following example sets the T11 timer to 90 seconds:
interface serial 0
x25 t11 90
Use the x25 t12 interface configuration command to set the value of the Reset Indication retransmission timer (T12) on DCE devices.
x25 t12 seconds| seconds | Amount of time in seconds. |
60 seconds
Interface configuration
The following example sets the T12 timer to 30 seconds:
interface serial 0
x25 t12 30
Use the x25 t13 interface configuration command to set the value of the Clear Indication retransmission timer (T13) on DCE devices.
x25 t13 seconds| seconds | Amount of time in seconds. |
60 seconds
Interface configuration
The following example sets the T13 timer to 30 seconds:
interface serial 0
x25 t13 30
Use the x25 t20 interface configuration command to set the value of the Restart Request retransmission timer (T20) on DTE devices.
x25 t20 seconds| seconds | Amount of time in seconds. |
180 seconds
Interface configuration
The following example sets the T20 timer to 90 seconds:
interface serial 0
x25 t20 90
Use the x25 t21 interface configuration command to set the value of the Call Request timer (T21) on DTE devices.
x25 t21 seconds| seconds | Amount of time in seconds. |
200 seconds
Interface configuration
The following example sets the T21 timer to 100 seconds:
interface serial 0
x25 t21 100
Use the x25 t22 interface configuration command to set the value of the Reset Request retransmission timer (T22) on DTE devices.
x25 t22 seconds| seconds | Amount of time in seconds. |
180 seconds
Interface configuration
The following example sets the T22 timer to 90 seconds:
interface serial 0
x25 t22 90
Use the x25 t23 interface configuration command to set the value of the Clear Request retransmission timer (T23) on DTE devices.
x25 t23 seconds| seconds | Amount of time in seconds. |
180 seconds
Interface configuration
The following example sets the T23 timer to 90 seconds:
interface serial 0
x25 t23 90
Use the x25 th interface configuration command to set the data packet acknowledgment threshold. When set, this parameter will instruct the router to send acknowledgment packets when it is not busy sending other packets, even if the number of input packets has not reached the input window size count. This command improves line responsiveness at the expense of bandwidth.
x25 th delay-count| delay-count | Value between zero and the input window size. A value of 1 sends one Receiver Ready acknowledgment per packet at all times. |
0 (which disables the acknowledgment threshold)
Interface configuration
The router sends an acknowledgment packet when the number of input packets reaches the count you specify, providing there are no other packets to send. For example, if you specify a count of 1, the router will send an acknowledgment per input packet if unable to "piggyback" the acknowledgment of an outgoing data packet.
The following example sends an explicit Receiver Ready acknowledgment when it has received five data packets that it has not acknowledged:
interface serial 1
x25 th 5
x25 win
x25 wout
Use the x25 use-source-address interface configuration command to over-ride the X.121 addresses of outgoing calls forwarded over a specific interface. Use the no x25 use-source-address command to prevent updating the source addresses of outgoing calls.
x25 use-source-addressThis command has no arguments or keywords.
Disabled
Interface configuration
Some X.25 calls, when forwarded by the X.25 switching support, need the calling (source) X.121 address updated to that of the outgoing interface. This is necessary when forwarding calls from private data networks to public data networks.
The following example shows how to prevent updating the source addresses of outgoing X.25 calls on interface serial 0 once calls have been forwarded:
interface serial 0
no x25 use-source-address
Use the x25 win interface configuration command to change the default incoming window size to match that of the network.
x25 win packets| packets | Packet count that can range from 1 to one less than the window modulus. |
2 packets
Interface configuration
This command determines the default number of packets a VC can receive before sending an X.25 acknowledgment. To maintain high bandwidth utilization, assign this limit the largest number that the network allows.
The following example specifies that five packets may be received before sending an X.25 acknowledgment:
interface serial 1
x25 win 5
x25 modulo
x25 th
x25 wout
Use the x25 wout interface configuration command to change the default outgoing window size to match that of the network.
x25 wout packets| packets | Packet count that can range from 1 to the window modulus. |
2 packets
Interface configuration
This command determines the default number of packets a VC can send before waiting for an X.25 acknowledgment. To maintain high bandwidth utilization, assign this limit the largest number that the network allows.
The following example specifies a default limit of five for the number of outstanding unacknowledged packets for VCs:
interface serial 1
x25 wout 5
x25 modulo
x25 th
x25 win
|
|