4000 Router Series MPLS Configuration Guide

higher than the holding priority of the existing tunnel. Both setup and holding priorities are in the

range of 0 to 7. A smaller value indicates a higher priority.

To avoid flapping caused by improper preemptions, the setup priority of a tunnel must not be

higher than its holding priority, namely, the setup priority value must be equal to or greater than

the holding priority value.

• Explicit path

Explicit path specifies the nodes to pass and the nodes to not pass for a tunnel.

Explicit paths include the following types:

{ Strict explicit path—Among the nodes that the path must traverse, a node and its previous hop

must be connected directly.

{ Loose explicit path—Among the nodes that the path must traverse, a node and its previous hop

can be connected indirectly.

Strict explicit path precisely specifies the path that an MPLS TE tunnel must traverse. Loose explicit

path vaguely specifies the path that an MPLS TE tunnel must traverse. Strict explicit path and loose

explicit path can be used together to specify that some nodes are directly connected and some

nodes have other nodes in between.

Setting up a CRLSP through RSVP-TE

After calculating a path by using CSPF, MPLS TE uses a label distribution protocol to set up the CRLSP and

reserves resources on each node of the path.

The device supports the label distribution protocol of RSVP-TE for MPLS TE. Resource Reservation Protocol

(RSVP) reserves resources on each node along a path. Extended RSVP can support MPLS label

distribution and allow resource reservation information to be transmitted with label bindings. This

extended RSVP is called "RSVP-TE."

For more information about RSVP, see "Configuring RSVP."

Traffic forwarding

After an MPLS TE tunnel is established, traffic is not forwarded on the tunnel automatically. You must

direct the traffic to the tunnel by using one of the following methods.

Static routing

You can direct traffic to an MPLS TE tunnel by creating a static route that reaches the destination through

the tunnel interface. This is the easiest way to implement MPLS TE tunnel forwarding. However, when the

traffic to multiple networks is to be forwarded through the MPLS TE tunnel, you must configure multiple

static routes, which are complicated to configure and difficult to maintain.

For more information about static routing, see Layer 3—IP Routing Configuration Guide.

Policy-based routing

You can configure PBR on the ingress interface of traffic to direct the traffic that matches an ACL to the

MPLS TE tunnel interface.

PBR can match the traffic to be forwarded on the tunnel not only by destination IP address, but also by

source IP address, protocol type, and other criteria. Compared with static routing, PBR is more flexible

but requires more complicated configuration.

For more information about policy-based routing, see Layer 3—IP Routing Configuration Guide.