Policy-based routing, Automatic route advertisement – H3C Technologies H3C SR8800 User Manual
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NOTE:
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, 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.
NOTE:
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 routers but not in the
IGP shortcut approach. Therefore, TE tunnels are visible to other routers in the forwarding adjacency
approach but not in the IGP shortcut approach.
Figure 17 IGP shortcut and forwarding adjacency
As shown in
, a TE tunnel is present between Router D and Router C. With IGP shortcut enabled,
the ingress node Router D can use this tunnel when calculating IGP routes. This tunnel, however, is
invisible to Router A; therefore, Router A cannot use this tunnel to reach Router C. With forwarding
adjacency enabled, Router A can known the presence of the TE tunnel and thus forward traffic to Router
C to Router D though this tunnel.