Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring an X.25 Datagram TransportConfiguring X.25 and LAPBsubinterface, the X.25 encapsulation process must be able to map the destination address of the datagramto a configured encapsulation command. If the routing process cannot find a map for the datagramdestination address, the encapsulation will fail.NoteBecause of the complex operations dependent on a subinterface and its type, the router will not allow asubinterface’s type to be changed, nor can a subinterface with the same number be reestablished once ithas been deleted. After a subinterface has been deleted, you must reload the Cisco IOS software (byusing the reload command) to remove all internal references. However, you can easily reconstitute thedeleted subinterface by using a different subinterface number.To configure subinterfaces on your X.25 network, perform the tasks in the section “Creating andConfiguring X.25 Subinterfaces,” next.Creating and Configuring X.25 SubinterfacesTo create and configure a subinterface, use the Step 1 command and one or both of the Step 2 commandsbeginning in global configuration mode:Step 1Step 2CommandRouter(config)# interface serial type number.subinterface-number[point-to-point | multipoint]Router(config-subif)# x25 map protocol address [protocol2 address2[... [protocol9 address9]]] x121-address [option]and/orRouter(config-subif)# x25 pvc circuit protocol address [protocol2address2 [...[protocol9 address9]]] x121-address [option]PurposeCreates a point-to-point ormultipoint subinterface.Configures an X.25encapsulation map for thesubinterface.Establishes an encapsulationPVC for the subinterface.For an example of configuring an X.25 subinterface and using multiple encapsulation commands for asingle destination address, see the section “Point-to-Point Subinterface Configuration Example” later inthis chapter.For more general information about configuring subinterfaces, refer to the chapter “Configuring SerialInterfaces” in the Cisco IOS Interface Configuration Guide.When configuring IP routing over X.25, you might need to make adjustments to accommodate splithorizon effects. Refer to the chapter “Configuring RIP” in the Cisco IOS IP Configuration Guide fordetails about possible split horizon conflicts. By default, split horizon is enabled for X.25 attachments.Mapping Protocol Addresses to X.121 AddressesThis section describes the X.25 single-protocol and multiprotocol encapsulation options that areavailable and describes how to map protocol addresses to an X.121 address for a remote host. Thefollowing sections include reference information about how protocols are identified:• Understanding Protocol Encapsulation for Single-Protocol and Multiprotocol VCs• Understanding Protocol IdentificationPerform the mapping tasks in the following sections, as necessary:20