Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring Additional X.25 Routing FeaturesConfiguring X.25 and LAPBStep 3 Router(config)# x25 hunt-group name {rotary |vc-count}Step 4CommandRouter(config)# x25 route [#position][selection-options] [modification-options]disposition-options [xot-keepalive-options]PurposeCreates the hunt group.Adds the hunt group to the routing table.For examples of configuring X.25 load balancing, see the section “X.25 Load Balancing Examples” laterin this chapter.Verifying X.25 Load BalancingTo verify X.25 load balancing, use the following command in EXEC mode:CommandRouter# show x25 hunt-groupPurposeDisplays hunt groups and detailed interface statistics and distribution methods.Configuring XOT to Use Interface Default Flow Control ValuesWhen a connection is set up, the source and destination XOT implementations must cooperate todetermine the flow control values that apply to the SVC. The source XOT ensures cooperation byencoding the X.25 flow control facilities (the window sizes and maximum packet sizes) in the X.25 Callpacket; the XOT implementation of the far host can then correctly negotiate the flow control values atthe destination interface and, if needed, indicate the final values in the X.25 Call Confirm packet.When XOT receives a call that leaves one or both flow control values unspecified, it supplies the values.The values supplied are a window size of 2 packets and maximum packet size of 128 bytes; accordingto the standards, any SVC can be negotiated to use these values. Thus when XOT receives a call from anolder XOT implementation, it can specify in the Call Confirm packet that these flow control values mustrevert to the lowest common denominator.The older XOT implementations required that the source and destination XOT router use the samedefault flow control values on the two X.25 interfaces that connect the SVC. Consequently, connectionswith mismatched flow control values were created when this assumption was not true, which resulted inmysterious problems. In the Cisco IOS Release 12.2 XOT implementation, the practice of signalling thevalues used in the Call Confirm packet avoids these problems.Occasionally the older XOT implementation will be connected to a piece of X.25 equipment that cannothandle modification of the flow control parameters in the Call Confirm packet. These configurationsshould be upgraded to use a more recent version of XOT; when upgrade is not possible, the behavior ofXOT causes a migration problem. In this situation, you may configure the Cisco IOS software to causeXOT to obtain unspecified flow control facility values from the default values of the destinationinterface.To configure this behavior, use the following command when enabling X.25 routing in globalconfiguration mode:CommandRouter(config)# x25 routing [tcp-use-if-defs]PurposeEnables X.25 routing and optionally modifies XOT source ofunencoded flow control values.36