3Com MSR 50 Series, Configuration Manual

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1354 C
HAPTER
77: MPLS TE C
ONFIGURATION
RSVP-TE advertises its GR capability and relevant time parameters to its neighbors
by extended RSVP Hello packets. If a device and all its neighbors have the RSVP GR
capability and have exchanged GR parameters, each of them can function as the
GR helper of another device.
When a GR restarter reboots, its GR helpers cannot receive Hello packets from it in
three Hello periods and hereby conclude that it is GR rebooting. Then, the GR
helpers retain soft state information about the GR restarter and keep sending
Hello packets periodically to the GR restarter until the restart timer expires.
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 will be removed. If
the recovery timer expires, soft state information and forwarding entries that are
not restored during the GR restarting process will be removed.
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With GR enabled, the device can act as only a GR helper.
Traffic Forwarding For traffic to travel along an LSP tunnel, you need to make configuration after
creating the MPLS TE tunnel. Otherwise, traffic will be 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 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.
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For more information about static routing, refer to “Static Routing and Dynamic
Routing” on page 817 .
Policy routing
You can also use policy routing to route traffic over an MPLS TE tunnel. In this
approach, you need to 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.
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For more information about policy routing, refer to the “IP Unicast Policy Routing
Configuration” on page 639 .
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.