Configuring the Ingress and Egress Router Addresses for LSPs

The following sections describe how to specify the addresses of an LSP’s ingress and egress routers:

Configuring the Ingress Router Address for LSPs

The local router always is considered to be the ingress router, which is the beginning of the LSP. The software automatically determines the proper outgoing interface and IP address to use to reach the next router in an LSP.

By default, the router ID is chosen as the address of the ingress router. To override the automatic selection of the source address, specify a source address in the from statement:

from address;

You can include this statement at the following hierarchy levels:

The outgoing interface used by the LSP is not affected by the source address that you configure.

Configuring the Egress Router Address for LSPs

When configuring an LSP, you must specify the address of the egress router by including the to statement:

to address;

You can include this statement at the following hierarchy levels:

When you are setting up a signaled LSP, the to statement is the only required statement. All other statements are optional.

After the LSP is established, the address of the egress router is installed as a host route in the routing table. This route can then be used by BGP to forward traffic.

To have the software send BGP traffic over an LSP, the address of the egress router is the same as the address of the BGP next hop. You can specify the egress router’s address as any one of the router’s interface addresses or as the BGP router ID. If you specify a different address, even if the address is on the same router, BGP traffic is not sent over the LSP.

To determine the address of the BGP next hop, use the show route detail command. To determine the destination address of an LSP, use the show mpls lsp command. To determine whether a route has gone through an LSP, use the show route or show route forwarding-table command. In the output of these last two commands, the label-switched-path or push keyword included with the route indicates it has passed through an LSP. Also, use the traceroute command to trace the actual path to which the route leads. This is another indication whether a route has passed through an LSP.

You also can manipulate the address of the BGP next hop by defining a BGP import policy filter that sets the route’s next-hop address.

Preventing the Addition of Egress Router Addresses to Routing Tables

You must configure an address using the to statement for all LSPs. This address is always installed as a /32 prefix in the inet.3 or inet.0 routing tables. You can prevent the egress router address configured using the to statement from being added to the inet.3 and inet.0 routing tables by including the no-install-to-address statement.

Some reasons not to install the to statement address in the inet.3 and inet.0 routing tables include the following:

To prevent the egress router address configured using the to statement from being added to the inet.3 and inet.0 routing tables, include the no-install-to-address statement:

no-install-to-address;

You can include this statement at the following hierarchy levels:

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