Configuring the IGPs for Traffic Engineering

For both IGPs, you must issue two commands to enable the IGP to support traffic engineering.

• IS-IS—Enable the flooding of MPLS traffic-engineering link information into the specified IS-IS level with the mpls traffic-eng command. You must also specify a stable router interface with the mpls traffic-eng router-id command.

  MPLS traffic engineering also 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 cannot interpret the new-style TLVs, use the metric-style transition command.

• OSPF—Enable OSPF areas for traffic engineering with the mpls traffic-eng area command. OSPF generates opaque LSAs—also known as type-10 opaque link area link states—to flood the traffic-engineering information to the specified area. OSPF builds a traffic-engineering database that it uses in the calculation of shortest path to destinations that satisfy specified traffic-engineering constraints. As with IS-IS, you must also specify a stable router interface with the mpls traffic-eng router-id command.

  To enable a multicast network and MPLS traffic engineering (TE) network to interoperate on a router running OSPF, use the mpls traffic-eng multicast-intact 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 designate the router as traffic engineering capable and to specify the router ID. For all tunnels that end at this node, set the tunnel destination to the destination node's traffic-engineering router identifier, because the traffic-engineering topology database at the tunnel ingress uses that for its path calculation.

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