AIS AI2524 user manual Understand X.25 Subaddresses, Configure an Interface Alias Address

Chapter 12: AI2524 X.25 Configuration Steps

destination of a received call if the destination address matches the in- terface's address.

The AI2524 X.25 software can also route X.25 calls, which involves placing and accepting calls, but the router is neither the source nor the destination for these calls. Routing X.25 does not modify the source or destination addresses, thus preserving the addresses specified by the source host. Routed (switched) X.25 simply connects two logical X.25 channels to complete an X.25 virtual circuit. An X.25 virtual circuit, is a connection between two hosts (the source host and the destination host) that is switched between routed X.25 links.

The null X.121 address (the X.121 address that has zero digits) is a special case. The router acts as the destination host for any call it re- ceives that has the null destination address.

Understand X.25 Subaddresses

A subaddress is an X.121 address that matches the digits defined for the interface's X.121 address, but has additional digit(s) after the base address. X.25 acts as the destination host for an incoming Packet As- sembler/Disassembler (PAD) call with a destination that is a subad- dress of the interface's address; the trailing digits specify which line a PAD connection is requesting. Other calls that use a subaddress can be accepted if the trailing digit(s) are zeros; otherwise, the router will not act as the call's destination host.

Configure an Interface Alias Address

You can supply alias X.121 addresses for an interface. This allows the interface to act as the destination host for calls having a destination ad- dress that is neither the interface's address, an allowed subaddress o the interface, nor the null address.

Local processing (for example, IP encapsulation) can be performed only for incoming calls whose destination X.121 address matches the serial interface or alias of the interface.

In global configuration mode, configure an alias:

x25 route [#position] x121-address-pattern [cud pattern] alias type number

August 1997	Page 12-11
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