|
|
Use the commands in this chapter to configure Link Access Procedure Balanced (LAPB), X.25, DDN X.25, and Blacker Front-end Encryption (BFE).
LAPB enables you to configure a simple, reliable serial encapsulation method. For historical background and a technical overview of X.25 and LAPB, see the Internetworking Technology Overview publication. For X.25 and LAPB configuration information and examples, refer to the "Configuring LAPB and X.25" chapter in the Access and Communication Servers Configuration Guide.
To configure an incoming access class on virtual terminals, use the access-class line configuration command.
access-class access-list-number in
access-list-number | An integer between 1 and 199 that you select for the access list |
in | Restricts incoming connections between a particular Cisco device and the addresses in the access list. |
No incoming access class is defined.
Line configuration
The access list number is used for both incoming TCP access and incoming PAD access.
In the case of TCP access, the communication server uses the IP access list defined using the access-list command.
For incoming PAD connections, the same numbered X.29 access list is referenced. If you only want to have access restrictions on one of the protocols, you can create an access list that permits all addresses for the other protocol.
The following example configures an incoming access class on virtual terminal line 4.
line vty 4
access-class 4 in
The dagger (†) indicates that the command is documented in another chapter of this manual.
access-list
line vty †
x29 access-list
Use the bfe EXEC command to set the communication server to participate in emergency mode or to end participation in emergency mode when your system is configured for x25 bfe-emergency decision and x25 bfe-decision ask.
bfe {enter | leave} interface type number
enter | Causes the communication server to send a special address translation packet that includes an enter emergency mode command to the BFE if the emergency mode window is open. If the BFE is already in emergency mode, this command enables the sending of address translation information. |
leave | |
interface | Permits you to specify an interface type and number. |
type | Interface type. |
number | Interface number. |
EXEC
The following example sets the communication server to participate in BFE mode:
bfe enter interface serial 0
encapsulation bfex25
x25 bfe-decision
x25 bfe-emergency
Use the clear x25-vc privileged EXEC command to clear virtual circuits.
clear x25-vc type number [lcn]
type | Interface type |
number | Interface number |
lcn | (Optional) Virtual circuit |
Privileged EXEC
This command without any arguments clears all X.25 virtual circuits at once.
The following example clears all virtual circuits:
clear x25-vc
x25 idle
To exchange datagrams over a serial interface using LAPB encapsulation, use the encapsulation lapb interface configuration command.
encapsulation lapb [dte | dce] [multi | protocol]
dte | (Optional) Specifies operation as a DTE. This is the default LAPB mode. |
dce | Optional) Specifies operation as a DCE. |
multi | (Optional) Specifies the use of multiple local-area network (LAN) protocols to be carried on the LAPB line. |
protocol | (Optional) A single protocol to be carried on the LAPB Line. It can be either ip or ipx (Novell IPX). IP is the default protocol. |
The default serial encapsulation is HDLC. You must explicitly configure a LAPB encapsulation method.
DTE operation is the default LAPB mode. IP is the default protocol.
Interface configuration
LAPB encapsulations are appropriate only for private connections, where you have complete control over both ends of the link. Connections to X.25 networks should use an x25 encapsulation configuration, which operates the X.25 Layer 3 protocol above a LAPB Layer 2.
One end of the link must be a logical DCE and the other end a logical DTE. (This assignment is independent of the interface's hardware DTE/DCE identity.)
Both ends of the LAPB link must specify the same protocol encapsulation.
A single-protocol LAPB encapsulation exchanges datagrams of the given protocol, each in a separate LAPB information frame. You should configure the interface with the protocol-specific parameters needed (for example, a link that carries IP traffic will have an IP address defined for the interface).
A multiprotocol LAPB encapsulation can exchange any or all of the protocols allowed for a single-protocol interface. It also exchanges datagrams, each in a separate LAPB information frame, although two bytes of protocol identification data precede the protocol data. You should configure the interface with all of the protocol-specific parameters needed for each protocol carried.
The following example sets the operating mode as DTE and specifies that IPX protocol traffic will be carried on the LAPB line:
interface serial 3
encapsulation lapb dte ipx
To specify an interface's operation as an X.25 device, use the encapsulation x25 interface configuration command.
encapsulation x25 [dte | dce] [[ddn | bfe] | [ietf]]
dte | (Optional) Specifies operation as a DTE. This is the default X.25 mode. |
dce | (Optional) Specifies operation as a DCE. |
ddn | (Optional) Specifies DDN encapsulation on a communication server using DDN X.25 standard Service. |
bfe | (Optional) Specifies BFE encapsulation on a communication server attached to a BFE device. |
ietf | (Optional) Specifies that the interface's datagram encapsulation should default to use of the IETF standard method, as defined by RFC 1356. |
The default serial encapsulation is HDLC. You must explicitly configure an X.25 encapsulation method.
DTE operation is the default X.25 mode. Cisco's traditional X.25 encapsulation method is the default.
Interface configuration
One end of an X.25 link must be a logical DCE and the other end a logical DTE. (This assignment is independent of the interface's hardware DTE/DCE identity.) Typically, when connecting to a public data network (PDN), the customer equipment acts as the DTE and the PDN attachment acts as the DCE.
Cisco has supported the encapsulation of a number of datagram protocols for quite some time, using a standard means when available and proprietary means when necessary. More recently the IETF adopted a standard, RFC 1356, for encapsulating most types of datagram traffic over X.25. X.25 interfaces use Cisco's traditional method unless explicitly configured for IETF operation; if the ietf keyword is configured, that standard will be used unless Cisco's traditional method is explicitly configured. For details see the x25 map command.
When an X.25 interface is reconfigured, all of the interface's X.25 parameters are initialized except the x25 map commands. The x25 map statements that are configured for an interface are not deleted when the encapsulation is changed, so they will be retained if the interface is later reconfigured for X.25 operation.
A communication server attaching to the Defense Data Network (DDN) or to a Blacker Front End (BFE) device can be configured to use their respective algorithms to convert between IP and X.121 addresses by using the ddn or bfe options, respectively. An IP address should be assigned to the interface, from which the algorithm will generate the interface's X.121 address; for proper operation, this X.121 address should not be modified.
A communication server DDN attachment can operate as either a DTE or a DCE device.A BFE attachment can operate only as a DTE device. The ietf option is not available if either the ddn or bfe option is selected.
The following example configures the interface for connection to a Blacker Front End device.
interface serial 0
encapsulation x25 bfe
Use the lapb hold-queue interface configuration command to define the number of packets to be held until they can be sent over the LAPB connection. 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 packets. A hold queue limit of 0 allows an unlimited number of packets in the hold queue. This argument is optional with the no form of the command. |
12 packets
Interface configuration
The following example sets the X.25 hold queue to hold 25 packets:
interface serial 0
lapb hold-queue 25
To specify a period during which a link will remain connected, even if a brief hardware outage occurs, use the lapb interface-outage interface configuration command.
lapb interface-outage milliseconds
milliseconds | Number of milliseconds a hardware outage can last without having the protocol disconnect the service. The default is 0 milliseconds. |
0 milliseconds, which disables this feature.
Interface configuration
If a hardware outage lasts longer than the LAPB hardware outage period you select, normal protocol operations will occur. The link will be declared to be down and, when it is restored, a link set up will be initiated.
The following example sets the interface outage period to 100 milliseconds. The link will remain connected for outages equal to or shorter than that period.
encapsulation lapb dte ip
lapb interface-outage 100
To specify the maximum permissible number of outstanding frames, called the window size, use the lapb k interface configuration command.
lapb k window-size
window-size | Frame count. It can be a value from 1 to the modulo size minus 1. The default is 7 frames. |
7 frames
Interface configuration
If the window size is changed while the protocol is up, the new value will take effect only when the protocol is reset. The operator will be informed that the new value will not take effect immediately.
When using the LAPB modulo 128 mode (extended mode), the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high-speed links that have a low error rate.
This configured value should match the value configured in the peer X.25 switch. Nonmatching values will cause repeated LAPB REJ frames.
The following example sets the LAPB window size (the k parameter) to ten frames:
interface serial 0
lapb modulo
lapb k 10
To specify the LAPB basic (modulo 8) or extended (modulo 128) protocol mode, use the lapb modulo interface configuration command.
lapb modulo modulus
modulus | Either 8 or 128. The value 8 specifies LAPB's basic mode; the value 128 specifies LAPB's extended mode. The default is 8. |
Modulo 8
Interface configuration
The modulo parameter determines which of LAPB's two modes is to be used. The modulo values derive from the fact that basic mode numbers information frames between 0 and 7, whereas extended mode numbers them between 0 and 127. Basic mode is widely available and is sufficient for most links. Extended mode is an optional LAPB feature that may achieve greater throughput on high-speed links that have a low error rate.
The LAPB operating mode may be set on X.25 links as well as LAPB Links. The X.25 layer modulo is independent of the LAPB layer modulo. Both ends of a link must use the same LAPB mode.
When using modulo 128 mode, the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high-speed links that have a low error rate.
If the modulo value is changed while the protocol is up, the new value will take effect only when the protocol is reset. The operator will be informed that the new value will not take effect immediately.
The following example configures a high-speed X.25 link to use LAPB's extended mode:
interface serial 1
encapsulation x25
lapb modulo 128
lapb k 40
clock rate 2000000
lapb k
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 32840; it must be a multiple of eight. |
12056 bits (1500 bytes)
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 organizations 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 8-1 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 | 8240 | 8256 |
2048 | 16440 | 16448 |
4096 | 32824 | 32832 |
Configuring N1 to be less than 2104 will generate a warning message that X.25 might 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 communication server so that 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 | Retransmission count from 1 through 255 |
20 retransmissions
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 a protocol on the LAPB line.
lapb protocol protocol
protocol | Protocol choice: ip and ipx (Novell IPX) |
IP
Interface configuration
The following example sets IP as the protocol on the LAPB line:
interface serial 1
lapb protocol ip
encapsulation lapb
encapsulation lapb-dce
Use the lapb t1 interface configuration command to set the limit retransmission timer period (the LAPB T1 parameter).
lapb t1 milliseconds
milliseconds | Number of milliseconds from 1 through 64000 |
3000 milliseconds
Interface configuration
The retransmission timer determines how long a transmitted frame can remain unacknowledged before the LAPB software polls for an acknowledgment.
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 20000 milliseconds:
interface serial 0
lapb t1 20000
To set the T4 idle timer, after which the system sends out a Poll packet to determine whether the link has suffered an unsignaled failure, use the lapb t4 interface configuration command.
lapb t4 seconds
seconds | Number of seconds between reception of the last frame and the transmission of the outgoing Poll; the default value is 0 seconds. |
0 seconds, which disables the T4 timer feature.
Interface configuration
Any non-zero T4 duration must be greater than T1, the LAPB retransmission timer period.
The following example will poll the other end of an active link if it has been 10 seconds since the last frame was received; if the far host has failed, the service will be declared down after N2 tries are timed out.
interface serial0
encapsulation x25
lapb t4 10
lapb t1
Use the show interfaces serial EXEC command to display information about a serial interface.
show interfaces serial number
number | Interface port number |
EXEC
The following is sample output from the show interfaces serial command for a serial interface using LAPB encapsulation:
cs# 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 8-2 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 to give to 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 sample output from the show interfaces serial command for a serial X.25 interface:
cs# 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
(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 8-3 describes significant fields shown in the display.
| Field | Description |
|---|---|
X25 address 000000010100 | Calling address used in the Call Request packet. |
state R1 | State of the interface. Possible values include:
If the state is R2 or R3, the device is awaiting acknowledgment for a Restart packet. |
modulo 8 | Modulo value; determines the packet sequence numbering scheme used. |
idle 0 | Number of minutes the communication server waits before closing idle virtual circuits. |
timer 0 | Value of the interface timer, which is zero unless the interface state is R2 or R3. |
nvc 1 | 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 size (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 communication server. |
Packet size: input 128, output 128 | Default packet size (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 communication server. |
Timers: T20 180, T21 200, T22 180, T23 180, TH 0 | Values of the Request packet timers:
|
Channels: Incoming-only none | Displays the channel sequence range 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. |
To display information about configured address maps, use the show x25 map EXEC command.
show x25 mapThis command has no arguments or keywords.
EXEC
The show x25 map command shows information about the following:
The following is sample output from the show x25 map command:
cs# show x25 map
Serial0: X.121 1311001 <--> ip 131.108.170.1
PERMANENT, BROADCAST, 2 VCS: 3 4*
Serial0: X.121 1311005 <--> ipx 128.1
PERMANENT
The display shows that two maps have been configured for the Serial0 interface.
Table 8-4 describes significant fields shown in the output displayed.
| Field | Description |
|---|---|
Serial0 | Interface on which this map is configured. |
X.121 1311001 | X.121 address of the mapped encapsulation host. |
IP 131.108.170.1 | Type and address of the higher-level protocol(s) mapped to the remote host. Bridge maps do not have a higher-level address; all bridge datagrams are sent to the mapped X.121 address. CLNS maps refer to a configured neighbor as identified by the X.121 address. |
PERMANENT | Address-mapping type that has been configured for the interface in this entry. Possible values include:
|
BROADCAST | If any options are configured for an address mapping, they will be listed; the example shows a maps that is configured to forward datagram broadcasts to the mapped host. |
2 VCS: | If the map has any active virtual circuits, they are identified. |
3 4* | Identifies the circuit number of the active virtual circuits. The asterisk marks the virtual circuit last used to send data. Note that a single protocol virtual circuit might be associated with a multiprotocol map. |
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:
cs# 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 8-5 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. |
To display information about active switched virtual circuits (SVCs) and permanent virtual circuits (PVCs), use the show x25 vc EXEC command.
show x25 vc [lcn]
lcn | (Optional) Logical channel number (LCN) |
EXEC
To examine a particular virtual circuit, add an LCN argument to the show x25 vc command.
This command displays information about virtual circuits that are used for any of the following:
The connectivity information displayed will vary according to the traffic carried by the virtual circuit. For multiprotocol circuits, the output varies depending on the number and identity of the protocols mapped to the X.121 address and the encapsulation method selected for the circuit.
This section provides three sample displays, which correspond to the four types of traffic information this command displays, and tables that describe the fields in each display.
The following sample display shows a virtual circuit that is being used to encapsulate traffic between the communication server and a remote host:
cs# show x25 vc 1024
SVC 1024, State: D1, Interface: Serial0
Started 0:00:31, last input 0:00:31, output 0:00:31
Connects 170090 <-->
compressedtcp 131.108.170.90
ip 131.108.170.90
multiprotocol cud pid, standard Tx data PID, Reverse charged
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Window is closed
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 8-6 describes the general fields shown in the output; Table 8-7 describes the fields specific to encapsulation virtual circuits shown in the output.
| Field | Description |
|---|---|
SVC 1024 | Identifies the type (switched or permanent) and the number of the virtual circuit. |
State | State of the virtual circuit (which is independent of the states of other virtual circuits); D1 is the normal ready state. (See the International Telecommunication Union Telecommunication Standardization Sector (ITU-T)1 X.25 Recommendation for a description of virtual circuit states.) |
Interface | Interface or subinterface 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. |
Connects...<-->... | Describes the traffic-specific connection information. See Table 8-7, Table 8-8, and Table 8-9 for more information. |
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. |
ACK | Last acknowledged incoming packet. |
Remote PR | 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 | This line appears if the communication server cannot transmit any more packets until the X.25 layer 3 peer has acknowledged some outstanding packets. |
Retransmits | Number of times a supervisory packet (RESET or CLEAR) has been retransmitted. |
Timer | A nonzero time value indicates that a supervisory packet has not been acknowledged yet or that the virtual circuit is being timed for inactivity. |
Reassembly | Number of bytes received and held for reassembly (packets with the More bit set are reassembled into datagrams for encapsulation virtual circuits; switched X.25 traffic does not reassemble). |
Held Fragments/Packets | Number of X.25 data fragments to transmit to complete an outgoing datagram, and the number of buffers held for transmission. |
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). |
| 1The ITU-T carries out the functions of the former Consultative Committee for International Telegraph and Telephone (CCITT). |
Table 8-7 describes the connection description fields for virtual circuits carrying encapsulation traffic.
| Field | Description |
|---|---|
170090 | The X.121 address of the remote host. |
ip 131.108.170.90 | The higher-level protocol and address values that are mapped to the virtual circuit. |
multiprotocol cud pid | Identifies the method used for the protocol identification (PID) in the Call User Data (CUD) field. Because PVCs are not set up using a Call packet, this field is not displayed for encapsulation PVCs. The available methods are as follows:
|
standard Tx data pid | Identifies the method used for protocol identification (PID) when sending datagrams. The available methods are as follows:
|
Reverse charged | Some important virtual circuit information might be displayed as needed; a DDN IP precedence encapsulation value, reverse charged virtual circuits, and virtual circuits that allow the D-bit procedure. |
The following sample display shows virtual circuits carrying locally switched X.25 traffic.
cs# show x25 vc
PVC 1, State: D1, Interface: Serial2
Started 0:01:26, last input never, output never
PVC <--> Serial1 PVC 1 connected
Window size input: 2, output: 2
Packet size input: 128, output: 128
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
SVC 5, State: D1, Interface: Serial2
Started 0:00:16, last input 0:00:15, output 0:00:15
Connects 170093 <--> 170090 from Serial1 VC 5
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 8-8 lists the connection description fields for virtual circuits carrying locally switched X.25 traffic.
| Field | Description |
|---|---|
PVC | Flags PVC information. |
Serial1 PVC1 | Identifies the other half of a local PVC connection. |
connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 8-10 for PVC status messages. |
170093 | Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. If the source host is a CMNS host, its MAC address will also be displayed. |
170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. If the destination host is a CMNS host, its MAC address will also be displayed. |
from Serial1 VC 5 | Indicates the direction of the call ("from" or "to") and the connecting interface and virtual circuit number. |
The following sample display shows virtual circuits carrying remotely switched X.25 traffic.
cs# show x25 vc
PVC 2, State: D1, Interface: Serial2
Started 0:01:25, last input never, output never
PVC <--> [131.108.165.92] Serial2/0 PVC 1 connected
XOT between 131.108.165.91, 1998 and 131.108.165.92, 27801
Window size input: 2, output: 2
Packet size input: 128, output: 128
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
SVC 6, State: D1, Interface: Serial2
Started 0:00:04, last input 0:00:04, output 0:00:04
Connects 170093 <--> 170090 from
XOT between 131.108.165.91, 1998 and 131.108.165.92, 27896
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 8-9 lists the connection description fields for virtual circuits carrying remotely switched X.25 traffic.
| Field | Description |
|---|---|
PVC | Flags PVC information. |
[131.108.165.92] | Indicates the IP address of the communication server remotely connecting the PVC. |
connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 8-10 for the PVC status messages. |
170093 | Identifies the Calling (source) Address if the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. |
170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. |
from | Indicates the direction of the call ("from" or "to"). |
XOT between... | Identifies the IP addresses and port numbers of the XOT connection. |
Table 8-10 lists the PVC states that can be reported. These states are also reported by the debug x25 command in PVC-SETUP packets (for remote PVCs only) as well as in the PVCBAD system error message. Some states apply only to remotely switched PVCs.
| Field | Description |
|---|---|
waiting to connect | The PVC is waiting to be processed for connecting. |
dest. disconnected | The other end disconnected the PVC. |
PVC/TCP connection refused | A remote PVC XOT TCP connection was tried and refused. |
PVC/TCP routing error | A remote PVC XOT TCP connection routing error was reported. |
PVC/TCP connect timed out | A remote PVC SOT TCP connection attempt timed out. |
trying to connect via TCP | A remote PVC XOT TCP connection is established and is in the process of connecting. |
awaiting PVD-SETUP reply | A remote PVC has initiated an XOT TCP connection and is waiting fro a reply to the setup message. |
connected | The PVC is up. |
no such dest. interface | The remote destination interface was reported to be in error by the remote communication server. |
dest interface is not up | The target interface's X.25 service is down. |
non-X.25 dest. interface | The target interface isn't configured for X.25. |
no such dest. PVC | The targeted PVC does not exist. |
dest PVC config mismatch | The targeted PVC is already connected. |
mismatched flow control values | The configured flow control values do not match. |
can't support flow control values | The window sizes or packet sizes of the PVC cannot be supported by one of its two interfaces. |
Use the x25 accept-reverse interface configuration command to instruct the communication server 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 sets 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. |
No X.121 address is assigned.
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 communication server configured for x25 bfe-emergency decision will participate in emergency mode.
x25 bfe-decision {no | yes | ask}
no | Prevents the communication server from participating in emergency mode and from sending address translation information to the BFE device. |
yes | Allows the communication server to participate in emergency mode and to send address translation information to the BFE when the BFE enters emergency mode. The communication server obtains this information from the table created by the x25 remote-red command. |
ask | Configures the communication server to display an onscreen request to enter the bfe EXEC command. |
no
Interface configuration
The following example shows how to configure serial interface 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 communication server will prompt the administrator for EXEC command bfe enter to direct the communication server 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 communication server participates in emergency mode.
x25 bfe-emergency {never | always | decision}
never | Prevents the communication server from sending address translation information to the BFE. If it does not receive address translation information, the BFE cannot open a new connection for which it does not know the address. |
always | Allows the communication server to pass address translations to the BFE when it enters emergency mode and an address translation table has been created. |
decision | Directs the communication server to wait until it receives a diagnostic packet from the BFE device indicating that the emergency mode window is open. The window is only open when a condition exists that allows the BFE to enter emergency mode. When the diagnostic packet is received, the communication server's participation in emergency mode depends on how it is configured using the x25 bfe-decision command. |
never
Interface configuration
The following example shows how to configure serial interface 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 communication server will prompt the administrator for EXEC command bfe enter to direct the communication server 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. |
No protocol is set.
Interface configuration
This command specifies the protocol assumed by the communication server to interpret incoming calls with unknown Call User Data. If you do not use the x25 default interface configuration command, the communication server clears any incoming calls with unknown Call User Data.
The following example establishes 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 override the default facility settings on a per-call basis for calls originated by the communication server. Use the no x25 facility command to disable the facility.
x25 facility facility-keyword value
facility-keyword | User facility; see Table 8-11 for a list of supported facilities and their values. |
value | Facility value; see Table 8-11 for a list of supported facilities and their values. |
| Option | Description |
|---|---|
cug number | |
packetsize in-size out-size | Specifies input packet size (in-size) and output packet size (out-size) for flow control parameter negotiation. Both values must be one of the following values: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. |
windowsize in-size out-size | Specifies the packet count for input windows (in-size) and output windows (out-size) for flow control parameter negotiation. Both values must be in the range 1 to 127 and must not be greater than the value set for the x25 modulo command. |
reverse | Specifies reverse charging on all calls originated by the interface. |
throughput in out | |
transit-delay value | Specifies a network transit delay for the duration of outgoing calls for networks that support transit delay. The transit delay value can be between 0 and 65334 milliseconds. |
rpoa name | Specifies the name defined by the x25 rpoa command for a list of transit Recognized Private Operation Agencies (RPOAs) to use in outgoing Call Request packets. |
No facility is sent.
Interface configuration
The following example specifies a transit delay value in an X.25 configuration:
interface serial 0
x25 facility transit-delay 24000
The following example specifies 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 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 incoming only. Incoming is from the perspective of the X.25 DTE. If you do not want any outgoing calls from your DCE, configure the lic and hic values and set the ltc and htc values to 0.
The following example sets 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 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 sets 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 virtual circuit packet hold queue size. A hold queue value of 0 allows an unlimited number of packets in the hold queue. This argument is optional with 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. An unlimited hold queue might be appropriate if the interface is configured with a maximum transmission unit (MTU) and IP MTU larger than the X.25 input packet size and X.25 output packet size. If you have configured an MTU and IP MTU larger than these packet sizes, our X.25 software will fragment the encapsulated IP packet into multiple X.25 frames. This fragmentation might cause the X.25 window to close and the hold queue to become full.
The following example sets 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 uses the Ignore Destination 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 communication server 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 following example sets the Ignore Destination 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 | |
x.121-address | The X.121 address. |
cud call-user-data | (Optional) Sets the Call User Data (CUD) field in the X.25 Call Request packet. |
No static host name-to-address mapping is defined.
Global configuration
The following example specifies a static address mapping:
x25 host Willard 4085551212
The following example removes 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
Interface configuration
This command is applicable if you have the X.25 switch configured for two-way.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0
x25 ltc 5
x25 htc 25
x25 ltc
The communication server 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 communication server to keep the SVC open indefinitely)
Interface configuration
Both calls originated and terminated by the communication server 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 sets a 5-minute wait period before an idle circuit is cleared:
interface serial 2
x25 idle 5
clear x25-vc
Use the x25 ips interface configuration command to set the interface default maximum input packet size to match those 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 communication server 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 sets the default maximum packet sizes to 512:
interface serial 1
x25 ips 512
x25 ops 512
x25 ops
Use the x25 ip-precedence interface configuration command to enable the ability to open a new virtual circuit based on the IP Type of Service (TOS) field. The command no x25 ip-precedence causes the TOS field to be ignored when opening virtual circuits.
x25 ip-precedenceThis command has no arguments or keywords.
The communication servers 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 TOS field, thus causing multiple, wasteful virtual circuits to be created.
The following example allows new virtual circuits based on the TOS field:
interface serial 3
x25 ip-precedence
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 incoming only. Incoming is from the perspective of the X.25 DTE. If you do not want any outgoing calls from your DCE, configure the lic and hic values and set the ltc and htc values to 0.
This command is applicable if you have the X.25 switch configured for two way virtual circuits.
The following example sets 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 disables 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 sets 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 two-way.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0
x25 ltc 5
x25 htc 25
x25 htc
To set up the LAN protocols-to-remote host mapping, use the x25 map interface configuration command. To retract a prior mapping, use the no form of the command with the appropriate network protocol(s) and X.121 address argument.
x25 map protocol1 address1 [protocol2 address2 [...[protocol9 address9]]] x.121-address
protocol | The protocol type. Supported protocols are entered by keyword, as listed in Table 8-12. You can specify as many as nine protocols in one command line. |
address | Protocol address. |
x.121-address | Specifies the X.121 address of the remote host. |
option | (Optional) Provides additional functionality or allows X.25 facilities to be specified for originated calls. Can be any of the options listed in Table 8-13. |
| Keyword | Protocol |
|---|---|
compressedtcp | TCP header compression |
ip | IP |
ipx | Novell IPX |
| Option | Description |
|---|---|
compress | |
method [cisco | ietf | snap | multi] | Specifies the encapsulation method. The choices are as follows:
|
no-incoming | Use the map only to originate calls. |
no-outgoing | Do not originate calls when using the map. |
idle minutes | Specifies an idle timeout for Calls other than the interface default; 0 minutes disables the idle timeout. |
reverse | Specifies reverse charging for outgoing calls. |
accept-reverse | Causes the communication server to accept incoming reverse-charged calls. If this option is not present, the system clears reverse charged calls unless the interface accepts all reverse charged calls. |
broadcast | Causes the system to direct any broadcasts sent through this interface to the specified X.121 address. This option also simplifies the configuration of OSPF; see "Usage Guidelines" for more detail. |
cug number | Specifies a closed user group number (from 1 to 99) for the mapping in an outgoing call. |
nvc count | Sets the maximum number of virtual circuits for this map/host. The default count is the x25 nvc setting of the interface. A maximum number of eight virtual circuits can be configured for each map. Compressed TCP may only use 1 virtual circuits. |
packetsize in-size out-size | |
windowsize in-size out-size | Proposes the packet count for input window (in-size) and output window (out-size) for an outgoing call. Both values are typically the same, must be in the range 1 to 127, and must be less than the value set by the x25 modulo command. |
throughput in out | |
transit-delay number | Specifies the transit delay value in milliseconds (0 to 65534) for an outgoing call, for networks that support transit delay. |
nuid username password | |
nudata string | |
rpoa name | Specifies the name defined by the x25 rpoa command for a list of transit RPOAs to use in outgoing Call Request packets. |
passive | Specifies that the X.25 interface should send compressed outgoing TCP datagrams only if they were already compressed when they were received. This option is available only for compressed TCP maps. |
No LAN protocol-to-remote host mapping is set up.
Interface configuration
Because no defined protocol can dynamically determine LAN protocol-to-remote host mappings, you must enter all of the information for each host with which the communication server may exchange X.25 encapsulated traffic.
Two methods are available to encapsulate traffic, Cisco's long-available encapsulation method and the IETF's standard method (defined in RFC 1356); the latter allows hosts to exchange several protocols over a single virtual circuit. Cisco's encapsulation method is the default (for backward compatibility, unless the interface configuration specified ietf).
When you configure multiprotocol maps, you can specify a maximum of nine protocol and address pairs in an x25 map command. However, you can specify a protocol once only. For example, you can specify the IP protocol and an IP address, but you cannot specify another IP address. If compressedtcp and ip are both specified, the same IP address must be used.
Bridging is supported only using Cisco's traditional encapsulation method. For correct operation, bridging maps must specify the broadcast option.
Because most datagram routing protocols rely on broadcasts or multicasts to send routing information to their neighbors, the broadcast keyword is needed to run such routing protocols over X.25.
Encapsulation maps might also specify that traffic between the two hosts should be compressed, thus increasing the effective bandwidth between them at the expense of memory and computation time. Each compression virtual circuit requires memory and computation resources, so compression should be used with care and monitored to maintain acceptable resource usage and overall communication server performance.
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 communication server. 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, and the ip ospf network command (with the broadcast keyword) is configured, there is no need to configure any neighbors manually. OSPF will now run over the X.25 network as a broadcast network. (Refer to the ip ospf network interface command for more detail.)
You can modify the options of an x25 map command by restating the complete set of protocols and addresses specified for the map, followed by the desired options. To delete a map command, you must also specify the complete set of protocols and addresses; the options can be omitted when deleting a map.
Once defined, a map's protocols and addresses cannot be changed; this is because the communication server cannot determine whether you want to add to, delete from, or modify an existing map's protocol and address specification (or simply mistyped the command). To change a map's protocol and address specification, you must delete it and create a new map.
A given protocol/address pair cannot be used in more than one map on the same interface.
The following example maps IP address 131.08.2.5 to X.121 address 000000010300. The broadcast keyword directs any broadcasts sent through this interface to the specified X.121 address.
interface serial 0
x25 map ip 131.08.2.5 000000010300 broadcast
The following example sets an RPOA name to be used when originating connections:
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 specifies a network user identifier (NUID) facility to send on calls originated for the address map:
interface serial 0
x25 map IP 131.108.174.32 2 nudata "Network User ID 35"
Strings can be quoted, but quotation marks are not required unless embedded blanks are present.
A dagger (†) indicates that the command is documented in another chapter.
ip ospf network †
show x25 map
x25 compress
x25 map bridge
x25 map cmns
x25 map compressedtcp
x25 rpoa
Use the x25 map compressedtcp interface configuration command to map compressed TCP traffic to X.121 addresses. The no x25 map compressedtcp command disables TCP header compression 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 8-13. |
No mapping of compressed TCP traffic to X.121 addresses.
Interface configuration
The Call User Data of compressed TCP calls is the single byte 0xD8.
TCP header compression is supported over X.25 links. The implementation of compressed TCP over X.25 uses a virtual circuit to pass the compressed packets. The noncompressed packets use another virtual circuit. The NVC map option cannot be used for TCP header compression, as only one virtual circuit can carry compressed TCP header traffic to a given host.
The following example establishes packet compression on serial interface 4:
interface serial 4
ip tcp header-compression
x25 map compressedtcp 131.08.2.5 000000010300
x25 map
Use the x25 modulo interface configuration command to set the packet numbering modulo.
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.
The following example sets the window modulus to 128:
interface serial 0
x25 modulo 128
x25 win
x25 wout
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.
x25 nvc count
count | Circuit count from 1 to 8. A maximum of eight virtual circuits 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 sets the maximum number of SVCs 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 those of the network.
x25 ops bytes
bytes | Byte count in the range of 16 through 1024 |
128 bytes
Interface configuration
X.25 networks use maximum input 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 communication server 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 sets the default maximum packet sizes to 512:
interface serial 1
x25 ips 512
x25 ops 512
x25 ips
To establish an encapsulation permanent virtual circuit (PVC), use the encapsulating version of the x25 pvc interface configuration command. To delete the PVC, use the no x25 pvc command with the appropriate channel number.
x25 pvc circuit protocol address [protocol address] x.121-address [option]
circuit | Virtual-circuit channel number, which must be less than the virtual circuits assigned to the switched virtual circuits (SVCs). |
protocol | Protocol type, entered by keyword. Supported protocols are listed in Table 8-14. As many as nine protocol and address pairs can be specified in one command line. |
address | Protocol address of the host at the other end of the PVC. |
option | (Optional) Provides additional functionality or allows X.25 parameters to be specified for the PVC. Can be any of the options listed in Table 8-15. |
| Keyword | Protocol |
|---|---|
ip | IP |
novell | Novell IPX |
compressedtcp | TCP header compression |
| Option | Description |
|---|---|
broadcast | Causes the communication server to direct any broadcasts sent through this interface to this PVC. This option also simplifies the configuration of OSPF; see the "Usage Guidelines" section for more information. |
method {cisco | ietf | snap | multi} | Specifies the encapsulation method. The choices are as follows:
|
packetsize in-size out-size | |
passive | Specifies that transmitted TCP datagrams will be compressed only if they were received compressed.This option is available only for PVCs carrying compressed TCP header traffic. |
windowsize in-size out-size |
No encapsulation PVC is established. 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 no longer need to specify a datagram protocol/address mapping before you can set up a PVC; a map is implied from the PVC configuration. Configurations generated by the communication server will no longer specify a map for encapsulating PVCs.
An X.121 address must be specified for the PVC, much as is done for an x25 map command, although the address does not appear in the PVC data exchange. When configuring a PVC to carry CLNS traffic, the X.121 address is used as the SNPA to associate the PVC with a CLNS neighbor configuration.
x25 map
Use the x25 remote-red interface configuration command to set up the table that lists the BFE nodes (host or gateways) to which the communication server will send packets.
x25 remote-red host-ip-address remote-black blacker-ip-address
host-ip-address | IP address of the host or a communication server 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. |
No BFE node is set up.
Interface configuration
The table that results from this command provides the address translation information the communication server sends to the BFE when it is in emergency mode.
The following example sets up a short table of BFE nodes for serial interface 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
Use the x25 rpoa global configuration command to set the packet network carrier. The no x25 rpoa command removes the specified name.
x25 rpoa name number1 [number2...number10]
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 | Number that is used to describe an RPOA; up to 10 numbers are accepted. |
No packet network carrier
Global configuration
This command lists transit RPOAs, referenced by name.
The following example sets an RPOA name and then sends 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 called 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 suppresses or omits 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 calling 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 suppresses or omits the calling address in Call Request packets:
interface serial 0
x25 suppress-calling-address
Use the x25 t10 interface configuration command to set the limit for the Restart Request 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 limit for the Call Request Completion 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 limit for the Reset Request 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 limit for the Clear Request 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 limit for 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 limit for the Call Request Completion 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 limit for 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 limit for 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 instruct the communication server to send an acknowledgment packet when it has received a threshold of data packets it has not acknowledged, instead of waiting until its input window is full. 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 delayed acknowledgment strategy)
Interface configuration
The communication server sends acknowledgment packets 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 communication server can send an acknowledgment per input packet.
The following example sends five Receiver Ready acknowledgments per packet as an input packet delay:
interface serial 1
x25 th 5
x25 win
x25 wout
Use the x25 win interface configuration command to change the default maximum number of unacknowledged incoming packets for the interface.
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 how many packets the communication server 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 must 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 maximum number of unacknowledged packets to allow.
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 the communication server 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 an upper limit of five for the number of outstanding unacknowledged packets for the output window:
interface serial 1
x25 wout 5
x25 modulo
x25 th
x25 win
To limit access to the communication server from certain X.25 hosts, use the x29 access-list global configuration command. To delete an entire access list, use the no form of this command.
x29 access-list access-list-number {deny | permit} x.121-address
access-list-number | Number of the access list. It can be a value between 1 and 199. |
deny | Denies access and clears call requests immediately. |
permit | Permits access to the protocol translator. |
x.121-address | X.121 address, with or without regular expression pattern-matching characters, with which to compare for access. |
No access lists are defined.
Global
An access list can contain any number of access list items. The list are processed in the order in which you entered them, with the first match causing the permit or deny condition. If an X.121 address does not match any of the regular expression in the access list, access will be denied.
Access lists take advantage of the message field defined by Recommendation X.29, which describes procedures for exchanging data between two PADs or a PAD and a DTE device.
The UNIX-style regular expression characters allow for pattern matching of characters and character strings in the address. Various pattern-matching constructions are available that will allow many addresses to be matched by a single regular expressions. Refer to the "Regular Expressions" appendix in this manual for more information.
The following example permits connections to hosts with addresses beginning with the string 31370:
x29 access-list 2 permit ^31370
To create a PAD profile script for use by the translate command, use the x29 profile global configuration command.
x29 profile name parameter:value [parameter:value]
name | Name of the PAD profile script. |
parameter:value | X.3 PAD parameter number and value separated by a colon. You can specify multiple parameter-value pairs. |
No PAD profile script is created.
Global configuration
When an X.25 connection is established, the communication server acts as if an X.29 SET PARAMETER packet had been sent containing the parameters and values set by the x29 profile command and sets the communication server accordingly.
The following profile script turns local edit mode on when the connection is made and establishes local echo and line termination upon receipt of a Return. The name "linemode" is used with the translate command to effect use of this script.
x29 profile linemode 2:1 3:2 15:1
A dagger (†) indicates that the command is documented in another chapter.
translate †
Posted: Mon Oct 21 12:22:13 PDT 2002
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