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AIXLink/X.25 1.1 for AIX: Guide and Reference

xroute Command


Enables the routing of calls that use the COMIO emulation.


xroute  [  -s  ]


The xroute command enables the routing of calls that use COMIO emulation for X.25 support. For applications that do not use this emulation interface, the xroute command is unnecessary. Applications such as xtalk, or SNA-based applications, have their calls routed by the table maintained by the xroute command.

Note: The xroute command works with X.25 ports that have COMIO emulation configured. Refer to "Managing COMIO Emulation" for further information.

All applications that use the COMIO emulation and wish to receive incoming calls, submit listen requests. These requests identify table entries in the emulator's routing table. Calls that are received are passed up from the X.25 port to the emulator and it determines if any application is listening for that call. The emulator is one of a number of applications, such as TCP/IP or NPI, that will be listening for incoming calls. The emulator provides extra routing capability which allows it to route the calls that its applications are expecting. Calls for applications like TCP/IP are not affected by the xroute command. If the incoming call matches the criteria defined in the routing table for a specific application, the call will be routed to that application. A routing table is not needed if you are using only permanent virtual circuits (PVCs).

An application listening for an incoming call is associated with an entry name in the routing table. This entry specifies the criteria that must be satisfied for the application program to receive an incoming call.

The call user data (CUD) field of the call packet is generally used for routing but other conditions may also be tested, such as:


-s Download the table to the emulator.

Updating the X.25 Routing Table with the xroute Command

The default routing table is stored in the /etc/xrt.names file. You can update this table with the xroute command by logging on as the root user and entering the following command:

xroute -s

This command displays the menu shown in the following X.25 Communications XROUTE Menu figure.

This is the default routing table with predefined entries for SNA, the sample program and the xtalk command. The first six entries correspond to X.25/SNA protocols:

IBMELLC Identifies the SNA enhanced logical link control (LLC) used for peer-to-peer communications.
IBMPSH Identifies the physical-services header LLC used with the IBM-5793 network interface adapter (NIA).
IBMQLLC Identifies the SNA qualified logical link control (QLLC).

The two CUDs associated with each of these protocols identify their version.

To change a routing list entry move the cursor to the entry name you would like to change and type c for CHANGE.

The dialog screen contains the following fields:

Entry Name Specifies the name of the entry the listening program uses to find the routing criteria.
Call User Data Indicates the part of the data received in an incoming call packet. It can be used for any purpose, but it often specifies the protocol. The xroute command uses only the first 64 bytes of the CUD.

For example, the CCITT defines the first four bytes of user data in a call from a packet assembler/disassembler (PAD) as hex 01000000. Enter this hex value in the CUD field of the routing table entry associated with an incoming PAD. The AIX/X.25 "Licensed Program" Product PAD does not use the xroute table.

User Name Specifies the login name of the user who is allowed to start applications listening for incoming calls associated with this entry. An * (asterisk) indicates that any user can listen for calls using this entry. A user whose login name does not match this entry is not allowed to listen for calls corresponding to it.

For example, your routing list entry contains the user name marcel , as in the following entry:

Entry Name   ==>IBMXTALK
User Name   ==>marcel

If you try to start the command xtalk -l IBMXTALK as the user root , the system displays an error message like the following:

CIO Status 79 - X25_AUTH_LISTEN
You cannot listen to this name, because the routing list entry has a userid which excludes the user running the application.
X.25 Port Specifies the name of the X.25 port associated with the application for which the call is intended. Use an * (asterisk) to indicate any port.
Calling Address Specifies the network user address (NUA) from which the application will receive incoming calls. An * (asterisk) at the end of this entry indicates that any digits are acceptable in the remainder of the address. Another NUA trying to call this application will be rejected.
Called Subaddress Specifies the NUA subaddress used to route a call internally within a node. You can add additional digits to the end of an NUA up to the 15-digit limit. Use an * (asterisk) for this parameter to indicate any subaddress.
Calling Address Ext Specifies the address extension for the calling DTE. The 1984 version of the X.25 protocol allows you to specify up to 40 additional digits of address. Use an * (asterisk) in this field to indicate any address extension.
Called Address Ext Specifies the address extension for the called DTE. The 1984 version of the X.25 protocol allows you to specify up to 40 additional digits of address. Use an * (asterisk) in this field to indicate any address extension.
Priority (1-3) Indicates the field that specifies when an application receives a call. If two applications need to listen to the same routing information, the priority field specifies which application receives the call if both are listening. For example, IBMSAMP is defined as listening to any condition (* in all fields), but with the lowest priority (3). Thus a background daemon could listen to IBMSAMP and log any incoming call that is not received by another application.
Action (R,F) Indicates the field that specifies whether to forward or reject an incoming call. The field values are R to reject the incoming call, or F to forward the incoming call. The forward or reject conditions apply when no application is listening for the routing list entry which is the best match for the incoming call.

If this field is set to R and your application is not running when you try to establish a call, the call will be cleared with cause 0 and diagnostic 0. If the field is set to F , the next best match is selected, and so on until an entry that specifies R is selected and the call is rejected.

If a call does not match any entry in the routing table, it is cleared with cause 0 and diagnostic 0.

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