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This chapter provides an introduction to using Cisco protocol translators. The emphasis here is on the various elements of a Cisco protocol translator's user interface. The following topics are addressed:
Please refer to the chapter, "First-Time Startup," for specifics concerning system configuration using the setup command facility. Refer to the chapter, "Configuring the System," for details about system-wide configuration features. See the chapter "Configuring Translation," about the translate command documented in this section. the chapter, "Managing the System," addresses facilities for monitoring and managing Cisco protocol translators. Configuration utilities associated with specific transmission protocols (TCP/IP, DEC LAT, IBM TN3270, X.25, and XRemote) are addressed in the"Transmission Protocols." section of this guide. If you have special applications, or wish to customize your connections, please refer to these other chapters for details.
Before exploring the specific connection commands provided with Cisco protocol translators, you should take time to familiarize yourself with the basic command line user interface. This section introduces you to the basic Cisco protocol translator user interface environment. This environment is generally referred to as the EXEC Command Interpreter (or EXEC).
The EXEC interprets the commands you type and carries out the corresponding operations. You can type commands when you see the system prompt, which is the host name followed by an angle bracket (>).
You may type commands in uppercase, lowercase, or both uppercase and lowercase letters. You may also abbreviate commands and other keywords to the number of characters that cause the command to be a unique abbreviation. For example, you can abbreviate the show command to sh.
If you make a typing mistake, you can erase characters with the Delete or the Backspace key. Press either key to erase the last character you typed. To erase the entire line, type Ctrl-U. (This notation means "Hold down the Ctrl key and press the U key.")
The protocol translator acts on most commands after you press the Return key. You can abort a command at any time by typing Ctrl-C.
To list available EXEC commands, type a question mark (?). You can often enter a question mark (help command) to obtain more information about commands. For example, type terminal ? to obtain a list of terminal commands or show ? to obtain a list of show commands.
Certain EXEC commands produce multiple screens of output. At the end of each screen, the EXEC pauses and displays:
-More-
Type a space to continue the output; type anything else to return to the system command prompt.
For security purposes, the EXEC has two levels of access: user and privileged. The commands available at the user level are a subset of the commands available at the privileged level. Because many of the privileged commands set protocol translator operating parameters, the privileged level should be password-protected to prevent its unauthorized use. The system prompt for the privileged level ends with a pound sign (#) instead of an angle bracket (>).
The enable command allows access to the privileged level, prompting for a password if one has been set with the enable password configuration command. For more information, see the "Establishing Passwords and System Security" section in the chapter "Configuring the System," of this manual. To list available EXEC commands, use the ? (question mark) command. At the user level, the ? command produces this list:
cpt>?
connect <host> Connect to host - same as typing just a host name
disconnect <cn> Break the connection specified by name or number
exit, quit Exit from the EXEC
lat <service> Connect to service using DEC LAT protocol
lock Lock the terminal
login Log in as a particular user
name-connection Give a connection a logical name
pad Connect to host using PAD protocol
resume Make the named connection be current
rlogin <host> Connect to host using rlogin protocol
show <cmd> Information commands, type "show ?" for list
systat Show terminal lines and users
telnet <host> Connect to host using telnet protocol
tn3270 <host> Connect to host using telnet protocol (3270)
terminal Change terminal's parameters, type "terminal ?"
where Show open connections
xremote Enter xremote mode
<cr> To resume connection
At the privileged level, the ? command lists the full protocol translator command set:
cpt#?
clear Reinitialization functions, type "clear ?" for list
configure Configure from terminal or over network
connect <host> Connect to host - same as typing just a host name
debug Enable debugging functions, type "debug ?" for list
disable Turn off privileged commands
disconnect <cn> Break the connection specified by name or number
enable Turn on privileged commands
exit, quit Exit from the EXEC
lat <service> Connect to service using DEC LAT protocol
lock Lock the terminal
login Log in as a particular user
name-connection Give a connection a logical name
pad Connect to host using PAD protocol
ping Send echo messages
reload Halt and reload system
resume Make the named connection be current
rlogin <host> Connect to host using rlogin protocol
send <line>|* Send message to a terminal line or lines
setup Initialize system configuration
show <cmd> Information commands, type "show ?" for list
systat Show terminal lines and users
telnet <host> Connect to host using telnet protocol
tn3270 <host> Connect to host using telnet protocol (3270)
terminal Change terminal's parameters, type "terminal ?"
test Run hardware tests, type "test ?"
trace <address> Trace route to <address>
undebug Disable debugging functions, type "undebug ?" for list
where Show open connections
write Write configuration memory, type "write ?" for list
xremote Enter xremote mode
<cr> To resume connection
Protocol translation allows two systems running different networking protocols to communicate as if the protocols were the same. This can be a difficult task, as networking protocols may require different numbers of network connections to run an application, or may have different formats for their data and commands.
For this reason, there may never be a protocol translator that handles electronic mail or file transfer in a completely transparent manner. Fortunately, there are fewer differences among protocols that connect remote terminals to a computer (called virtual terminal protocols).
The protocol translator attempts to provide transparent protocol translation between systems running disparate protocols. Cisco protocol translation fully-supports two-way virtual terminal protocol translation between nodes running X.25, DEC LAT, and TCP/Telnet. Limited translation (two-step only) is supported for XRemote (to X.25 PAD environments) and TN3270 (to LAT, X.25, and TCP/Telnet). This allows terminal users on one network to access hosts (or host-like devices) on another network, despite differences in the native protocol stacks associated with the originating device and the target host. You can use either of two methods to accomplish this, as discussed in the following sections.
The one-step method invokes a translation session process to provide fully transparent protocol conversion. In this method, the protocol translator masquerades as two or more hosts on the same network. When a connection is made to the protocol translator, it determines which host the connection is for, and what protocol that host is using. It then establishes a new network connection, using the networking protocol required by that host.
This has the advantage of being simpler from the users' point of view. It is more efficient, and allows the protocol translator to act upon greater knowledge of the protocols in use, as the protocol translator acts as a network connection rather than a terminal. One disadvantage, however, is that the initiating computer or user does not know that two networking protocols are being used. This creates the limitation that parameters of the foreign network protocols cannot be changed, once the connections are established.
The exception to this limitation is the set of parameters common to both networking protocols. Any parameter in this set can be changed, from the first host to the final destination.
To support connections in each direction, you must specifically include translate command statements in the configuration file to handle bi-directional connections.
A typical one-step translation application might feature a UNIX workstation user attempting a connection to a remote X.25 host, named host1, over an X.25 PDN. In this case, the protocol translator automatically converts the Telnet connection request to an X.25 connection request and transmits the request as specified in the system configuration.
A connection is established by first entering the telnet command at the UNIX workstation system prompt, as follows:
unix%telnet host1
The protocol translator accepts the Telnet connection, and immediately forms an outgoing connection with the remotely-located host1 as specified in a translate command specified in your protocol translator's active configuration file. Next, host1 sets several X.3 parameters, including local echo. Since the Telnet connection is already set to local echo (at the UNIX host), no changes are made on the TCP connection.
The host1 connection prompts for a user name, which is provided (and echoed locally), as follows:
login name:
Then host1 sets the X.3 parameter to cause remote echo (the same process as setting X.3 PAD parameter 2:0), and prompts for a password. The protocol translator converts this to a Telnet option request on the UNIX host, which then stops the local echo mode.
At this point the user is connected to the PAD application and the application will set the X.3 PAD parameters (although they can always be overridden by the user). When the user is finished with the connection, he enters the escape character to exit back to the host connection, then enters the appropriate command to close the connection.
The host1 host immediately closes the X.25 connection. The protocol translator then drops the TCP connection, leaving the user back at the UNIX system prompt.
In the two-step method, a user explicitly establishes a network connection to a protocol translator, and from there establishes an outgoing network connection on a different type of network. The two steps are:
Step 1: Establish the incoming connection directly to the protocol translator.
Step 2: Establish the outgoing connection established from the protocol translator to another network host.
This process is similar to connecting a group of terminal lines from a PAD, to a group of terminal lines from a TCP terminal server. The difference is that you do not encounter the wiring complexity, unreliability, management problems, and performance bottlenecks that occur when two separate devices are connected via asynchronous serial lines. With the two-step connection process, a user can individually modify the parameters of either network connection, even while a session is in process.
The protocol translator supports the two-step model in both directions (for example, from Telnet to PAD, and the reverse).
If you use the two-step method to connect, you can change PAD and local terminal parameters dynamically during a session.
The following example shows how you might make a dynamic change during a session. Suppose that you wanted to type in some information at the Information Place, and need to change the X.3 PAD parameters that define the editing characters from the default Delete key setting to the Ctrl-D sequence.
To do this you would first enter the escape sequence to return to the protocol translator system EXEC:
Ctrl-^X
Then at the EXEC, type in the resume command (discussed in the chapter "Using the Protocol Translator") with the /set keyword and the desired X.3 parameters.
cpt>resume /set 16:4
You may also want to set the /debug switch to check that your parameter setting has not been changed by the host PAD. The /debug switch provides helpful information about the connection.
At the EXEC, you may also set a packet dispatch character or sequence using the terminal dispatch-character command. The dispatch-character line subcommand is discussed in the chapter "Configuring the System." This example shows how to set ESC as a dispatch character using the EXEC command version of dispatch-character:
cpt>terminal dispatch-character 27
To return to the PAD connection, simply enter:
cpt>resume
Now you may use your new settings for your session.
The first step in any two-step translation is to connect directly from a terminal or workstation to a protocol translator. For example, a user might make the following connection request:
unix_host%telnet cpt
If a protocol translator named cpt is reachable, it returns a login message and the user enters a user name and password. The next step then requires that the user connect from the protocol translator to some target system. For example, the user might attempt a connection to an X.25 host using the pad command. The user might enter the following:
cpt>pad 71330
Once the connection is established, the protocol translator immediately sets the PAD to single character mode with local echoing, since this is the behavior the protocol translator expects. The PAD responds with its login messages and a prompt for a password:
Trying 71330...Open
Welcome to the Information Place
Password:
As the password should not echo on the user's terminal, the PAD requests remote echoing so that characters will be exchanged between the PAD and the protocol translator, but not echoed locally or displayed. After the password is verified, the PAD again requests local echoing from the protocol translator, which it does from then on.
Eventually, the user logs off, and is returned to the protocol translator system EXEC prompt. From there, the user executes the quit command and the protocol translator drops the network connection to the PAD.
Please refer to the chapter, "Configuring X.25 and X.3," for details about the pad command.
Users can make simple automated terminal-to-host connections, or can establish custom terminal sessions tailored to specific terminal or application requirements. The following connection descriptions define the basic connection capabilities available to users and the syntax associated with each user level EXEC connection command. Refer to the appropriate chapters of this manual, "Transmission Protocols," for details about protocol-related customization of terminal characteristics. The commands outlined here represent the basic connection services provided by Cisco protocol translators for DEC LAT, Telnet, TN3270, XRemote, and X.25.
You can change the default connection protocols discussed in this section by using the transport commands. For more information about the transport commands refer to the chapter, "Configuring the System."
DEC's Local Area Transport (LAT) protocol is the protocol used most often to connect protocol translators to DEC hosts. LAT is a DEC-proprietary protocol. Cisco uses LAT technology licensed from DEC.
The LAT protocol is similar to TCP/IP's Telnet protocol in that it allows a user at one site to establish a connection to a host at another site, then passes the keystrokes from one system to the other. A user can establish a LAT connection through the protocol translator to a DEC host, simply by entering the host name.
Use the EXEC command lat to establish a connection to a LAT learned service. The command has this syntax:
lat name [node nodename| port portname | /debug]Enter this command at the EXEC prompt. It can be entered simply by typing the name of the service to which you want to attach, or with the optional keywords listed in the above syntax description. You can also enter the service name to make the connection.
The optional keyword node specifies connection to a specific LAT node which offers a service. Enter the name of the node in place of the nodename argument. If you do not include the node option, the node with the highest rating offering the service is used. Use the EXEC command show lat nodes to display information about all known LAT nodes (see the section "Monitoring LAT" in the chapter "Configuring LAT," for more information about this command).
The optional keyword port specifies a destination LAT port name. This keyword is ignored in most timesharing systems, but is used by terminal servers offering reverse LAT services. Enter the port name in the format of the remote system in place of the portname argument.
Reverse LAT services are discussed in the section "Inbound Session Support," in the chapter "Configuring LAT." Generally, reverse LAT involves connecting to a terminal server from a protocol translator. In this case, the target terminal server runs the host portion of the protocol.
The optional keyword /debug is a switch that, when enabled, prints parameter changes and other special messages on the terminal.
The following example establishes a LAT connection from the protocol translator named cpt to the host Eng2.
cpt>lat eng2
Trying ENG2...Open
ENG2 - VAX/VMS V5.2
Username:JSmith
Password:
Welcome to VAX/VMS version V5.2 on node ENG2
Last interactive login on Friday, 6-APR-1990 19:46
The LAT protocol is explicitly specified in this example. You specify the protocol when your preferred transport is set to "none" or to another protocol. The protocol translator responds with "Trying <system>..." and then "Open." If the connection were not successful you would receive a failure message. Refer to the chapter, "Configuring the System," for more information about setting terminal preferences.
The rlogin command starts a connection using the UNIX rlogin protocol. The full syntax of the command follows:
rlogin host [debug]The argument host is a host name or an Internet address. The optional keyword debug enables debugging output from the rlogin protocol.
An alternative to the Telnet protocol, the rlogin protocol provides superior flow control and output suppression. The Cisco implementation of rlogin does not subscribe to the "trusted" host model. That is, a user cannot automatically log onto a UNIX system from the protocol translator, but must provide a user ID and a password for each connection.
For more information concerning rlogin connections, please refer to the chapter, "Configuring TCP/IP," later in this manual.
This section addresses the basics of making Telnet connections. For more information concerning TCP/IP connections, please refer to the chapter, "Configuring TCP/IP," later in this manual.
Use the EXEC command connect or telnet to start a Telnet connection. The command has this syntax:
{connect | telnet} host [port] [/keyword]The argument host is a host name or an Internet address. The optional argument port is a decimal TCP port number; the default is the Telnet server port (decimal 23) on the host. The optional argument keyword is one of the following:
cpt>connect mathom /route:kl.sri.com 10.1.0.11 mathom
The protocol translator assigns a logical name to each connection; several commands use these names to identify connections. The logical name is the same as the host name, unless that name is already in use or you change the connection name with the EXEC command name-connection. If the name is already in use, the protocol translator assigns a null name to the connection.
If your network administrator has configured an appropriate default terminal type, then using the EXEC command tn3270 is all you need to enter to start a tn3270 session via a Cisco protocol translator. The syntax for this command is as follows:
tn3270 hostnameThe argument hostname is the name of a specific host on a network that is reachable by the protocol translator. The default terminal emulation mode allows access using a VT100 emulation. If your terminal requires a different emulation, you must configure your protocol translator to support different terminal types.
The following example use of the EXEC command tn3270 results in the Cisco protocol translator attempting to establish a terminal session with an IBM host named finance.
cpt>tn3270 finance
Establishing connections using alternative configurations (which must be included in the Cisco protocol translator configuration) is explained in the next section. The process for configuring the Cisco protocol translator to include alternative (and custom) terminal emulations is outlined in the chapter, "Configuring TN3270," later in this manual.
If your host computer includes a server for XDMCP, such as the xdm program included in X11R4, you can use automatic session startup to initiate an XRemote session on an NCD X terminal.
The EXEC command used to initiate XRemote using XDMCP is xremote xdm. This command has the following syntax:
xremote xdm hostnameThis command causes an XDMCP session start-up request to be made to the computer specified (hostname). If a hostname is not specified, a broadcast message is sent to all hosts. The first host to respond by starting up a session is used.
The protocol translator and X terminal stay in XRemote mode until either the display manager terminates the session, or a reset request is received from the X terminal.
Cisco protocol translators support the use of X.25 as a transport mechanism for IP-based traffic. As you would expect, this capability covers Telnet, connect and rlogin connection commands, but also extends to XRemote and TN3270. Refer to the chapter, "Configuring X.25 and X.3," for complete details concerning configuration requirements for setting up X.25 encapsulation on protocol translators.
This capability is most useful on protocol translators with a serial network interface. From a user's point of view, connections are relatively transparent when making a remote connection over a PDN. In general, users simply make a connection request.
ts>telnet far_host
If properly configured, the protocol translator takes this connection request, encapsulates the IP-based frame in an X.25 packet and sends it over the X.25 PDN to a specified location (based on the X.121 address). At the remote location, a Cisco router takes the request, de-encapsulates the X.25 packet, and puts the IP-based frame on the appropriate network. If all goes well, a virtual terminal connection is then made between the originating node and the target host.
The protocol translator supports connections to an X.3 PAD host.
To make a connection to a PAD host, enter the pad command followed by the X.25 host address and press Return. The basic syntax is as follows:
pad X.121-addressIf the X.25 host name has been defined with the x25 host name command, you can enter the host name rather than the host address. In addition, one-word PAD connections are supported, allowing you to simply enter the host name or X.121 address to make a connection.
When you are finished, logging off the host will end your connection. The EXEC terminates any connection after 10 minutes of inactivity or when you enter the exit command.
The pad command offers options that allow it to support X.3 functionality and to display the PAD parameters set by either a host or an application. These options and PAD Recommendation X.3 are discussed in the chapter, "Configuring X.25 and X.3."
The following user level commands and facilities are applicable to all transmission protocols supported by Cisco protocol translators using the two-step translation method:
You can have several concurrent connections open and switch back and forth between them. The number of connections that may be opened is defined by the session-limit command. Refer to the chapter, "Configuring the System." To switch between connections, first type the escape sequence, which by default is Ctrl-^, X (press the Ctrl, Shift and ^ key simultaneously, let go, then press the X key), to return to the system command prompt.
To make a new connection, use the procedure described in "Starting a Telnet Connection," or "Starting an Rlogin Connection," above. To get back to an existing connection, use the resume command, described next. Use the where command to list your open connections.
The EXEC resume command returns to a previous connection. The general form is available with all connection protocols supported by the protocol translator. The general command syntax is as follows:
resume [connection]The optional argument connection is the connection name or number; the default is the most recent connection.
You can omit the command word resume and simply type the connection number to resume a connection. You can also return to the most recent session by just pressing the Return key.
Use the EXEC command login to log in to a system with a specific user name. This command can be used to change your login name. One reason to change your login name is that an outgoing access list may depend on the specification of a particular user name. Refer to the discussion regarding Cisco's TACACS (and other user authentication) facilities in the chapter, "Configuring the System." In addition, IP access lists are discussed in the chapter, "Configuring TCP/IP." The syntax for the login command is:
loginThe system returns prompts for user name and password. If both are entered correctly, your session becomes associated with the specified user name. If there is no match, your connection to the terminal server reverts to the user name with which the login command attempt was made, if applicable. If no login name and password were originally required, the connection reverts to a session that is not associated with any name.
In the example below a user named foouser wants to change the login name being used to sloan. After entering the login command, the new name is entered along with an incorrect password. The system rejects the attempt to change user name. Next foouser attempts to change the login name to klaus. This time the correct password is entered and the user is now allowed access at the user level prompt under the user name of klaus.
sys-prompt>login
Username:sloan
Password:
% Access denied
Still logged in as "foouser"
sys-prompt>login
Username:klaus
Password:
sys-prompt>
If you want to prevent access to your protocol translator session while keeping your connection sessions online, use the lock EXEC command. This command has the following syntax:
lockThe effect of this command is to lock your keyboard. It requires that the global configuration command lockable be included in your system configuration (described in the chapter, "Configuring the System"). The lock EXEC command remains in effect until the clear line privileged EXEC command (described in the chapter "Managing the System") is executed. If you are able to lock your session, you will be prompted to specify a password, which can be any arbitrary string. Enter the password you want to assign. The screen clears and displays the message "Locked." To regain access to your sessions, reenter the password. The protocol translator honors session timeouts on a locked line.
The EXEC command where displays information about all open Telnet or rlogin connections associated with the current terminal line. The command has this simple syntax:
whereFollowing is a sample display:
cpt>where
Conn Host Address Byte Idle Conn Name
1 STUFT 131.108.19.50 0 0 STFUT
* 2 OTTER 192.31.7.24 0 0 OTTER
The information it displays includes the host name, address, number of characters waiting to be sent to the terminal, idle time, and connection name. An asterisk (*) indicates the current connection.
The name-connection command assigns a logical name to a connection. The EXEC prompts for the connection number and name to assign when you enter this command. The where command displays a list of the assigned logical connection names.
The following example checks the connection number for the host Eng1, assigns the logical name my host to it, and then confirms the assignment.
cpt>where
Conn Host Address Byte Idle Conn Name
* 1 Eng1 192.31.6.22 0 0 Eng1
2 Term2 192.33.6.21 0 0 Term2
cpt>name-connection
Connection number:1
Enter logical name: my host
Connection 1 to Eng1 will be named "my host" [confirm]
cpt>where
Conn Host Address Byte Idle Conn Name
* 1 Eng1 192.31.6.22 0 0 my host
The EXEC command disconnect aborts a connection, and has this syntax:
disconnect [connection]The optional argument connection is a connection name or number; the default is the current connection. To list your open connection, use the where command.
The following example checks the open connections, and closes the connection to Eng1, which has the logical name of my host.
cpt>where
Conn Host Address Byte Idle Conn Name
* 1 Eng1 192.31.6.22 0 0 my host
2 Term2 192.33.6.21 0 0 Term2
cpt>disconnect my host
Closing connection to Eng1 [confirm]
To display information about your active terminal sessions, use the show sessions EXEC command. This command has the following syntax:
show sessions
Conn Host Address Byte Idle Conn Name
* 1 GUN 131.222.3.11 0 0 GUN
2 BIG 131.222.3.14 0 5 BIG
The information it displayed includes the host name, address, number of characters waiting to be sent to the terminal, idle time, and connection name. An asterisk (*) indicates the users's current session.
The EXEC command show terminal displays the configuration parameter settings for the current terminal line. Enter this command at the EXEC prompt:
show terminalFollowing is a sample display of the command's output:
cpt>show terminal
Line 3, Location: "Library x1234", Type: ""
Length: 24 lines, Width: 80 columns
Baud rate (TX/RX) is 9600/9600, no parity, 2 stopbits, 8 databits
The escape character is "^^", followed by "x"
The local hold character is disabled
No flowcontrol in effect.
Status: Ready, Active
Capabilities: none
Idle EXEC timeout is 10 minutes.
Idle session timeout is not set.
Modem answer timeout is 15 seconds
Dispatch timeout is not set.
Allowed transports are telnet rlogin. Preferred is telnet
Disconnect character is not set
Activation character is ^M (13)
No output characters are padded
Characters causing immediate data dispatching:
Char ASCII
The display includes a comprehensive report on the terminal settings in effect, including the preferred transport protocol.
The EXEC command systat displays information about the active ports of the protocol translator, and has this syntax:
systat [all]A sample display follows:
cpt>systat all
Line User Host(s) Idle Location
0 con 0 otter console
1 tty 1 Bill x1234
2 tty 2 DAVE-SS2 1:32 Dave x1235
* 3 tty 3 STUFT 0 Denise x1236
4 tty 4 incoming 11:17 remote.host.com
5 tty 5 Sam- ROM emulator
6 tty 6 CD4 ???
7 tty 7 Teresa x1236
10 tty 10 STUFT 3 Mark x1237
11 tty 11 HEAT 1 Eng32-1
12 tty 12 STUFT 17:32 CD8 ???
13 tty 13 1525: Sandy x1238
14 tty 14 MEDDLE 23 Marsha x1239
15 tty 15 Randy x1240
16 tty 16 Kevin x2120
17 tty 17 Robert x2141
20 tty 20 Bill x2142
21 tty 21 Laser printer
22 tty 22 ""
The information it displays includes the line number, connection name, idle time, and terminal location. The optional keyword all requests information about both active and inactive ports.
The exit or quit command terminates the EXEC command parser and closes any active terminal sessions. Enter either command when you are finished with all sessions.
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