Chapter 12: AI2524 X.25 Configuration Steps
August 1997 Page 12-11
2524UM
destination of a received call if the destination ad d ress 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 modi fy the source or
destination addresses, thus preserving the addresses specified by the
source host. Routed (switched) X .2 5 simpl y 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 di git(s ) after the base
address. X.25 acts as the destination h ost 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 us e a s ubaddress can be
accepted if the trailing digit(s) are zeros; oth erwis e , 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 e nca ps u la tion) 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, config ur e an alias:
x25 route [
#position
]

x121-address-pattern

[cud

pattern

] alias
type number