IS-IS Parameter Default ValueCircuit Type Level 1 and Level 2IS Type Level 1 and Level 2Equal Cost Multi Paths 16Configuration InformationTo use IS-IS, you must configure and enable IS-IS in two or three modes: CONFIGURATION ROUTERISIS, CONFIGURATION INTERFACE, and ( when configuring for IPv6) ADDRESS-FAMILY mode.Commands in ROUTER ISIS mode configure IS-IS globally, while commands executed in INTERFACEmode enable and configure IS-IS features on that interface only. Commands in the ADDRESS-FAMILYmode are specific to IPv6.NOTE: When using the IS-IS routing protocol to exchange IPv6 routing information and todetermine destination reachability, you can route IPv6 along with IPv4 while using a single intra-domain routing protocol. The configuration commands allow you to enable and disable IPv6routing and to configure or remove IPv6 prefixes on links.Except where identified, the commands described in this chapter apply to both IPv4 and IPv6 versions ofIS-IS.Configuration Tasks for IS-ISThe following describes the configuration tasks for IS-IS.• Enabling IS-IS• Configure Multi-Topology IS-IS (MT IS-IS)• Configuring IS-IS Graceful Restart• Changing LSP Attributes• Configuring the IS-IS Metric Style• Configuring IS-IS Cost• Changing the IS-Type• Controlling Routing Updates• Configuring Authentication Passwords• Setting the Overload Bit• Debuging IS-ISEnabling IS-ISBy default, IS-IS is not enabled.The system supports one instance of IS-IS. To enable IS-IS globally, create an IS-IS routing process andassign a NET address. To exchange protocol information with neighbors, enable IS-IS on an interface,instead of on a network as with other routing protocols.In IS-IS, neighbors form adjacencies only when they are same IS type. For example, a Level 1 router neverforms an adjacency with a Level 2 router. A Level 1-2 router forms Level 1 adjacencies with a neighboringLevel 1 router and forms Level 2 adjacencies with a neighboring Level 2 router.NOTE: Even though you enable IS-IS globally, enable the IS-IS process on an interface for the IS-ISprocess to exchange protocol information and form adjacencies.474 Intermediate System to Intermediate System
