Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring X.25 and LAPBConfiguring X.25 RoutingWhen the connection is made locally, the switching configuration is used; when the connection is acrossa LAN, the XOT configuration is used. The basic function is the same for both types of connections, butdifferent configuration commands are required for each type of connection.The X.25 switching subsystem supports the following facilities and parameters:• D-bit negotiation (data packets with the D-bit set are passed through transparently)• Variable-length interrupt data (if not operating as a DDN or BFE interface)• Flow control parameter negotiation:– Window size up to 7, or 127 for modulo 128 operation– Packet size up to 4096 (if the LAPB layers used are capable of handling the requested size)• Basic CUG selection• Throughput class negotiation• Reverse charging and fast selectThe handing of these facilities is described in the appendix “X.25 Facility Handling.”To configure X.25 routing, perform the tasks in the following sections:• Enabling X.25 Routing• Configuring an X.25 Route• Configuring a PVC Switched Between X.25 Interfaces• Configuring X.25 Switching Between PVCs and SVCsSee the section “Configuring Additional X.25 Routing Features” for further configuration options foryour network.Enabling X.25 RoutingYou must enable X.25 routing to use switch VCs.To enable X.25 routing, use the following command in global configuration mode:CommandRouter(config)# x25 routing [use-tcp-if-defs]PurposeEnables X.25 routing.The use-tcp-if-defs keyword is used by some routers that receive remote routed calls from older versionsof XOT; it might be needed if the originating router cannot be updated to a new software release. Theuse of this keyword is described in the section “Configuring XOT to Use Interface Default Flow ControlValues” later in this chapter.For examples of configuring X.25 routing, see the sections “X.25 Route Address Pattern MatchingExample” and “X.25 Routing Examples” later in this chapter.31