Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring X.25 RoutingConfiguring X.25 and LAPBConfiguring an X.25 RouteAn X.25 route table enables you to control which destination is selected for several applications. Whenan X.25 service receives a call that must be forwarded, the X.25 route table determines which X.25service (X.25, CMNS, or XOT) and destination should be used. When a PAD call is originated by therouter, either from a user request or from a protocol translation event, the route table similarlydetermines which X.25 service and destination should be used.You create the X.25 route table and add route entries to it. You can optionally specify the order of theentries in the table, the criteria to match against the VC information, and whether to modify thedestination or source addresses. Each entry must specify the disposition of the VC (that is, what is donewith the VC). Each route can also specify XOT keepalive options.The route table is used as follows:• VC information is matched against selection criteria specified for each route.• The table is scanned sequentially from the top.• The first matching route determines how the VC is handled.• Once a matching entry is found, the call addresses can be modified and the call disposed of(forwarded or cleared) as instructed by the entry.Each application can define special conditions if a route will not be used or what occurs if no routematches. For instance, switched X.25 will skip a route if the disposition interface is down and clear acall if no route matches. X.25 PAD and PAD-related applications, such as protocol translation usingX.25, will route the call to the default X.25 interface, which is the first X.25 interface configured.To configure an X.25 route (thus adding the route to the X.25 routing table), use the following commandin global configuration mode:CommandRouter(config)# x25 route [#position] [selection-options][modification-options] disposition-options [xot-keepalive-options]PurposeConfigures an X.25 route.The following options offer versatility and flexibility when you use the x25 route command:• #position—Position in the table. You can use the optional #position element to indicate the numberof the entry in the route able. For example, #9 indicates the ninth entry from the top. The route tableis always searched sequentially from the top, and the first match found will be used.• selection-options—Criteria to define to which VCs the route will apply. You can match against zeroto four of the following optional selection elements:– destination-pattern– source source-pattern– dest-ext nsap-destination-pattern– cud user-data-pattern• modification-options—Modifications to the source or destination address for address translation.You can use neither, one, or both of the following optional modification elements to change thesource or destination address before forwarding the call to the destination:– substitute-source rewrite-source– substitute-dest rewrite-destination32