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If a GR helper and the GR restarter reestablish a Hello session before the restart timer expires, the
recovery timer is started and signaling packet exchanging is triggered to restore the original soft state.
Otherwise, all RSVP soft state information and forwarding entries relevant to the neighbor are removed.
If the recovery timer expires, soft state information and forwarding entries that are not restored during the
GR restarting process are removed.
The switch, if configured with RSVP-TE GR, can act as both a GR restarter and a GR helper.
The devices that have no backup MPUs can act as only GR helpers when they are configured with
RSVP-TE GR.
Traffic forwarding
For traffic to travel along an LSP tunnel, you must perform the configuration after creating the MPLS TE
tunnel. Otherwise, traffic is IP routed.
Even when an MPLS TE tunnel is available, traffic is IP routed if you do not configure it to travel the tunnel.
For traffic to be routed along an MPLS TE tunnel, you can use static routing, policy-based routing, or
automatic route advertisement.
Static routing
Static routing is the easiest way to route traffic along an MPLS TE tunnel. You only need to manually
create a route that reaches the destination through the tunnel interface.
For more information about static routing, see Layer 3—IP Routing Configuration Guide.
Policy-based routing
You can also use policy-based routing to route traffic over an MPLS TE tunnel. In this approach, create a
policy that specifies the MPLS TE tunnel interface as the output interface for traffic that matches certain
criteria defined in the referenced ACL.
This policy should be applied to the incoming interface.
For more information about policy-based routing, see Layer 3—IP Routing Configuration Guide.
Automatic route advertisement
You can use automatic route advertisement to advertise MPLS TE tunnel interface routes to IGPs, allowing
traffic to be routed down MPLS TE tunnels.
Two approaches are available to automatic route advertisement—IGP shortcut and forwarding
adjacency.
OSPF and IS-IS support both approaches where TE tunnels are considered point-to-point links and TE
tunnel interfaces can be set as outgoing interfaces.
IGP shortcut, also known as autoroute announce, considers a TE tunnel as a logical interface directly
connected to the destination when computing IGP routes on the ingress of the TE tunnel.
IGP shortcut and forwarding adjacency are different in that in the forwarding adjacency approach,
routes with TE tunnel interfaces as outgoing interfaces are advertised to neighboring devices but not in
the IGP shortcut approach. Therefore, TE tunnels are visible to other devices in the forwarding adjacency
approach but not in the IGP shortcut approach.
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