Configuring IS-IS for MPLS

IS-IS has several commands to provide support for MPLS. See JunosE BGP and MPLS Configuration Guide, for a detailed discussion of MPLS. If you configure your tunnel with the tunnel mpls autoroute announce isis command, MPLS attempts to register the tunnel endpoint with IS-IS. You must enable this registration with IS-IS by issuing the mpls traffic-eng command.

When you configure a node as the downstream endpoint of an LSP, you must provide a stable interface as the router ID for the endpoint. Typically you select a loopback interface because of its inherent stability. Use the mpls traffic-eng router-id command to specify the router ID.

By default, IS-IS always uses the MPLS tunnel to reach the MPLS endpoint. Best paths determined by IS-IS SPF calculations are not considered. You can enable the consideration of best paths by issuing the mpls spf-use-any-best-path command. As a result, IS-IS considers metrics for IGP paths and the tunnel metric, and might forward traffic along a best path, through the MPLS tunnel, or both.

Several show commands enable monitoring of MPLS information. See Monitoring IS-IS for more information.

MPLS traffic engineering requires that IS-IS generate the new-style TLVs that enable wider metrics. Use the metric-style wide command to generate the new-style TLVs. If you are using some IS-IS routers that still do not understand the new-style TLVs, use the metric-style transition command. See Extensions for Traffic Engineering and Configuring Global IS-IS Parameters for detailed information about using the metric-style commands.