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Configuring X.25

Configuring X.25

This chapter describes how to configure a Cisco 1600 series router to connect to a central-site router over an X.25 line or over an Integrated Systems Digital Network (ISDN) line and provides verification steps and troubleshooting tips.

This chapter contains the following sections:

Before You Begin

The configurations in this chapter are based on the following assumptions:

Before you begin configuration, be aware of the following:

Note In order to use the verification steps described in this chapter, you must be familiar with Cisco IOS commands and command modes. When you use the verification steps, you need to change to different command modes. If you are not familiar with command modes, refer to the "Understanding Command Modes" section in the "Cisco IOS Basic Skills" chapter.

X.25

This section describes how to your router for a point-to-point X.25 WAN connection to the central-site router.

These are the major tasks when configuring your router:

Figure 6-1 illustrates the configuration used in this example.


Figure 6-1: X.25 Example Configuration



Configuring Global Parameters

Use this table to configure the router for some global parameters, including IPX routing and how log and debug messages are timestamped.

Step Task Router Prompt Command
1 . 
 Enter configuration mode. Router# configure terminal
2 . 
 Configure the router to show the date and time of all debug messages.

This command is optional, but recommended if you use debug commands to troubleshoot your configuration.

 Router(config)# service timestamps debug datetime msec
3 . 
 Configure the router to show the date and time of all log messages.

This command is optional, but recommended if you use the verification steps described in this guide. This feature is enabled for all the example command output shown in this guide.

 Router(config)# service timestamps log datetime msec
4 . 
 Enable IPX routing and configure the router with an IPX address. Router(config)# ipx routing 0060.834f.66dd

Configuring Security

Use this table to configure the router with some security measures, such as the router host name and the password used to prevent unauthorized access to the router.

Step Task Router Prompt Command
1 . 
 Configure the router with a host name, which is used in prompts and default configuration file names.

For Point-to-Point Protocol (PPP) authentication, the host name entered with this command must match the username of the central-site router.

 Router(config)# hostname 1600
2 . 
 Specify a password to prevent unauthorized access to the router. 1600(config)# enable password 1600user

Configuring the Ethernet Interface

Use this table to configure the Ethernet interface (which connects the router to your local network) for IP and IPX routing and network addresses.

Step Task Router Prompt Command
1 . 
 Enter configuration mode for the Ethernet interface. 1600(config)# interface Ethernet0
2 . 
 Configure this interface with an IP address and a subnet mask. 1600(config-if)# ip address 172.16.25.42 255.255.255.224
3 . 
 Configure this interface with an IPX network number. 1600(config-if)# ipx network ABC
4 . 
 Enable the interface and the configuration changes that you have just made on the interface. 1600(config-if)# no shutdown
5 . 
 Exit configuration mode for this interface. 1600(config-if)# exit

Configuring the X.25 Interface

Use this table to configure the X.25 interface for the following:

Step Task Router Prompt Command
1 . 
 Enter configuration mode for the serial interface. 1600(config)# interface Serial0
2 . 
 Configure this interface with an IP address. 1600(config-if)# ip address 172.16.26.1 255.255.255.0
3 . 
 Set the encapsulation type on this interface to X.25. 1600(config-if)# encapsulation x25
4 . 
 Enable IPX routing on this interface. 1600(config-if)# ipx network 9876
5 . 
 Set the X.121 address of this interface. 1600(config-if)# x25 address 5432
6 . 
 Set up the LAN protocols-to-remote-host mapping for IP and X.25. 1600(config-if)# x25 map ip 172.16.26.2 2345 broadcast
7 . 
 Set up the LAN protocols-to-remote-host mapping for IPX and X.25. 1600(config-if)# x25 map ipx 9876.0000.0c03.ecc6 2345 broadcast
8 . 
 Enable the interface and the configuration changes that you have just made on the interface. 1600(config-if)# no shutdown
9 . 
 Exit configuration mode for this interface. 1600(config-if)# exit

Verifying Your Configuration

You can verify your configuration to this point by

Confirming Connectivity to the Central-Site Router Over IP

Step 1 Confirm that the router is connected to the central-site router.

Step 2 From the privileged EXEC command mode, enter the ping command followed by the IP address of the central-site router:

Step 3 Confirm that the success rate shown in the output (shown in bold in the example) is 60 percent (3/5) or greater. This means that your router is successfully transferring data to the central-site router.

Step 4 To continue configuration, re-enter global configuration mode.

Confirming Connectivity to the Central-Site Router Over IPX

Step 1 Confirm that the router is connected to the central-site router.

Step 2 From the privileged EXEC command mode, enter the ping command.

Step 3 Respond to the prompts shown in the following example:

Step 4 Confirm that the success rate shown in the output (shown in bold in the example) is 60 percent (3/5) or greater. This means that your router is successfully transferring data to the central-site router.

Step 5 To continue configuration, re-enter global configuration mode.

Confirming That the Serial Interface Is Functioning Correctly

Step 1 From the privileged EXEC command mode, enter the show interface serial 0 command.

Step 2 Check that the "line protocol is up" and the "State CONNECT" messages (shown in bold in the example) appear in the command output:

Step 3 If you do not see these messages, refer to the following "Troubleshooting X.25 Problems" section for suggestions.

Step 4 To continue configuration, re-enter global configuration mode.

Confirming That the X.25 Map Is Configured Correctly

Step 1 From the privileged EXEC command mode, enter the show x25 map command:

Step 2 Confirm that your IPX network number and the central-site router IP address and IPX address appear in the command output (shown in bold in the example). The IP and IPX addresses shown in your output are different than those shown above.

Confirming Switched Virtual Circuit and Permanent Virtual Circuit Information

Step 1 From the privileged EXEC command mode, enter the show x25 vc command, as follows:

Step 2 Look for the following messages in the output (shown in bold in the example):

Step 3 To continue configuration, re-enter global configuration mode.

Configuring Command Line Access to the Router

Use this table to configure some parameters that control access to the router, including the type of terminal line used with the router, how long the router waits for a user entry before it times out, and the password used to start a terminal session with the router.

Step Task Router Prompt Command
1 . 
 Specify the console terminal line. 1600(config)# line console 0
2 . 
 Set the interval that the EXEC command interpreter waits until user input is detected. 1600(config-line)# exec-timeout 5
3 . 
 Specify a virtual terminal for remote console access. 1600(config-line)# line vty 0 4
4 . 
 Specify a password on the line. 1600(config-line)# password lineaccess
5 . 
 Enable password checking at terminal session login. 1600(config-line)# login

Troubleshooting X.25 Problems

If you are having problems or the output that you received during the verification steps is very different from what is shown, you can troubleshoot your router by taking some or all of the following actions:

Caution If you are not familiar with Cisco IOS debug commands, you should read the "Using Debug Commands" section in the "Cisco IOS Basic Skills" chapter before attempting any debugging.

X.25 Over ISDN B Channel

This section describes how to configure the router to encapsulate IP and IPX packets as X.25 and route them over an ISDN B-channel connection.

In addition to the assumptions described in the "Before You Begin" section in this chapter, this configuration is based on the assumption that you can only use one of the two ISDN B channels for this type of configuration.

These are the major tasks when configuring your router:

Figure 6-2 illustrates the configuration used in this example.


Figure 6-2: X.25 over ISDN B Channel Example Configuration



Configuring Global Parameters

Use this table to configure the router for some global parameters, including the ISDN switch type that the router is connected to through the ISDN line, IPX routing, and how log and debug messages are timestamped.

Step Task Router Prompt Command
1 . 
 Enter configuration mode. Router# configure terminal
2 . 
 Configure the router to show the date and time of all debug messages.

This command is optional, but recommended if you use debug commands to troubleshoot your configuration.

 Router(config)# service timestamps debug datetime msec
3 . 
 Configure the router to show the date and time of all log messages.

This command is optional, but recommended if you use the verification steps described in this guide. This feature is enabled for all the example command output shown in this guide.

 Router(config)# service timestamps log datetime msec
4 . 
 Enable IPX routing and configure the router with an IPX address. Router(config)# ipx routing 0060.834f.66dd
5 . 
 Configure the type of central office switch being used on the ISDN interface. Use the keyword that matches the ISDN switch type that you are using:

  • basic-ts013 --Australian TS013 switches

  • basic-1tr6 --German 1TR6 ISDN switches

  • basic-nwnet3--Norway NET3 switches (phase 1)

  • basic-net3--NET3 ISDN switches

  • vn2--French VN2 ISDN switches

  • vn3--French VN3 ISDN switches

  • ntt--Japanese NTT ISDN switches

  • basic-5ess--AT&T basic rate switches

  • basic-dms100--NT DMS-100 basic rate switches

  • basic-ni--National ISDN-1 switches

  • basic-nznet3--New Zealand Net3 switches

Router(config)#

isdn switch-type basic-ni
6 . 
 Enter configuration mode for the ISDN interface. Router(config)# interface bri0
7 . 
 Enable the ISDN switch type configuration for the ISDN interface. Router(config-if)# no shutdown
8 . 
 Exit configuration mode for the ISDN interface. Router(config-if)# exit

Verifying Your Configuration

You can verify your configuration to this point by confirming the ISDN line status as follows:

Step 1 From the privileged EXEC command mode, enter the show isdn status command.

Step 2 Confirm that the "State = MULTIPLE_FRAME_ESTABLISHED" message (shown in bold in the example) appears on the command output:

Step 3 If you don't see the message, do the following:

Step 4 To continue configuration, re-enter global configuration mode.

Configuring Security

Use this table to configure the router with some security measures, including the password used to access the router and the username and password used for Challenge Handshake Authentication Protocol (CHAP) and Password Authentication Protocol (PAP) authentication with the central-site router.

Step Task Router Prompt Command
1 . 
 Configure the router with a host name, which is used in prompts and default configuration file names.

For Point-to-Point Protocol (PPP) authentication, the host name entered with this command must match the username of the central-site router.

 1600(config)# hostname 1600
2 . 
 Specify a password to prevent unauthorized access to the router. 1600(config)# enable password 1600user
3 . 
 Specify the password used during caller identification and CHAP and PAP authentication.

For CHAP and PAP authentication, the username entered with this command must match the host name of the central-site router.

 1600(config)# username HQ password guessme

Configuring the Ethernet Interface

Use this table to configure the Ethernet interface with an IP address.

Step Task Router Prompt Command
1 . 
 Enter configuration mode for the Ethernet interface. 1600(config)# interface Ethernet0
2 . 
 Configure this interface with an IP address. 1600(config-if)# ip address 192.168.38.42 255.255.255.0
3 . 
 Enable the interface and the configuration changes that you have just made on the interface. 1600(config-if)# no shutdown
4 . 
 Exit configuration mode for this interface. 1600(config-if)# exit

Configuring the ISDN Interface for X.25

Use this table to configure the ISDN interface for X.25 packet encapsulation and IP and IPX routing parameters.

Step Task Router Prompt Command
1 . 
 Enter configuration mode for the ISDN interface. 1600(config)# interface BRI0
2 . 
 Configure this interface with an IP address. 1600(config-if)# ip address 192.168.41.41 255.255.255.0
3 . 
 Set the encapsulation type on this interface to X.25. 1600(config-if)# encapsulation x25
4 . 
 Enable snapshot routing. Because your router is dialing into a central-site router, it is considered the client router.

The first number is the amount of "active time" (in minutes) during which routing updates are exchanged between your router and the central-site router.

The second number is the amount of "quiet time" (in minutes) during which routing entries are frozen and remain unchanged.

 1600(config)# snapshot client 5 60
5 . 
 Enable IPX routing on this interface. 1600(config-if)# ipx network 9876
6 . 
 Set the X.121 address of this interface. 1600(config-if)# x25 address 5432
7 . 
 Set up the LAN protocols-to-remote-host mapping for X.25 to IP. 1600(config-if)# x25 map ip 192.168.39.40 2345 broadcast
8 . 
 Set up the LAN protocols-to-remote-host mapping for IPX and X.25. x25 map ipx 9876.0000.0c03.ecc6 2345 broadcast
9 . 
 Configure this interface to place a call to multiple sites and to authenticate calls from multiple sites based on IP address and dialer string.

The name you enter after the name keyword in this command must match the name entered with the username command in the previous "Configure Security" section.

 1600(config-if)# dialer map ip 192.168.39.40 name HQ 5558461
10 . 
 Configure this interface to place a call to multiple sites and to authenticate calls from multiple sites based on IP address and dialer string.

The name you enter after the name keyword in this command must match the name entered with the username command in the previous "Configure Security" section.

 1600(config-if)# dialer map ipx 9876.0000.0c03.e336 name HQ 5558461
11 . 
 Assign this interface to a dialer group. 1600(config-if)# dialer-group 1
12 . 
 Define a DDR dialer list to control dialing based on access lists and IP packets. 1600(config-if)# dialer-list 1 protocol ip permit
13 . 
 Define a DDR dialer list to control dialing based on access lists and IPX packets. 1600(config-if)# dialer-list 1 protocol ipx permit

Verifying Your Configuration

You can verify your configuration to this point by:

Confirming Connectivity with the Central-Site Router Over IP

Step 1 Confirm that your router X.25 connection is active.

Step 2 From the privileged EXEC command mode, enter the ping command followed by the IP address of the central-site router:

Step 3 Confirm that the success rate shown in the output (shown in bold in the example) is 60 percent (3/5) or greater. This means that your router is successfully transferring data to the central-site router.

Step 4 To continue configuration, re-enter global configuration mode.

Confirming Connectivity to the Central-Site Router Over IPX

Step 1 Confirm that your router X.25 connection is active.

Step 2 Enter the ping command followed by the IPX address of the central-site router:

Step 3 Confirm that the success rate shown in the output (shown in bold in the example) is 60 percent (3/5) or greater. This means that your router is successfully transferring data to the central-site router.

Step 4 To continue configuration, re-enter global configuration mode.
Confirming That the X.25 Map Is Configured Correctly

Step 1 From the privileged EXEC command mode, enter the show x25 map command:

Step 2 Confirm that the following addresses (shown in bold in the example) appear in the command output:

Step 3 To continue configuration, re-enter global configuration mode.

Confirming Switched Virtual Circuit and Permanent Virtual Circuit Information

Step 1 From the privileged EXEC command mode, enter the show x25 vc command.

Step 2 Confirm that the X.25 address is associated with the correct IP and IPX addresses (shown in bold in the example).

Step 3 To continue configuration, re-enter global configuration mode.

Configuring Command Line Access to the Router

Use this table to configure some parameters that control access to the router, including the type of terminal line used with the router, how long the router waits for a user entry before it times out, and the password used to start a terminal session with the router.

Step Task Router Prompt Command
1 . 
 Specify the console terminal line. 1600(config)# line console 0
2 . 
 Set the interval that the EXEC command interpreter waits until user input is detected. 1600(config-line)# exec-timeout 5
3 . 
 Specify a virtual terminal for remote console access. 1600(config-line)# line vty 0 4
4 . 
 Specify a password on the line. 1600(config-line)# password lineaccess
5 . 
 Enable password checking at terminal session login. 1600(config-line)# login
6 . 
 Exit configuration mode. 1600(config-line)# end

Troubleshooting Problems with X.25 over ISDN B Channel

If you are having problems or the output that you received during the verification steps is very different from what is shown, you can troubleshoot your router by taking some or all of the following actions:

Caution If you are not familiar with Cisco IOS debug commands, you should read the "Using Debug Commands" section in the "Cisco IOS Basic Skills" chapter before attempting any debugging.

How X.25 Works

X.25 is a method of packet-switching that is used for communication between user devices (such as routers, bridges, and host machines) and network devices (such as switching nodes and modems). User devices are called data terminal equipment (DTE) and network devices are called data circuit-terminating equipment (DCE)

With X.25, one computer calls another to request a communication session. The called computer can accept or refuse the connection. If the call is accepted, the two computers begin full-duplex information transfer. Either computer can terminate the connection at any time.

User devices communicate with a bidirectional association called a virtual circuit. Devices on a network use virtual circuits to communicate through intermediate nodes without being directly, physically connected to each other. Virtual circuits are permanent or switched (temporary). Permanent virtual circuits (PVCs) are typically used for the most-often-used data transfers and switched virtual circuits (SVCs) are used for sporadic data transfers.

Basic Rate Interface (BRI) is an ISDN interface consisting of two B channels (B1 and B2) and one D channel. The B channels are used to transfer data, voice, and video. The D channel carries signal and call setup information. IPX, AppleTalk, transparent bridging, XNS, DECnet, and IP can all be encapsulated as X.25 over the ISDN B channels.

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