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JUNOS Cookbook by Aviva Garrett

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14.11. Protecting an LSP's Path

Problem

You want to protect an LSP's traffic in the event of a link or router failure to ensure that it always arrives at the egress end of the LSP.

Solution

When you create an LSP, RSVP establishes a single path between the ingress and egress routers. One way to protect the LSP's path is to establish an end-to-end secondary path for the LSP. First, explicitly set up the primary LSP:

	[edit protocols mpls]
	aviva@R1# set label-switched-path R1-to-R5 to 10.0.0.5
	aviva@R1# set label-switched-path R1-to-R5 bandwidth 50m
	aviva@R1# set label-switched-path R1-to-R5 primary primary-path-R1-to-R5
	aviva@R1# set path primary-path-R1-to-R5

Then, configure a secondary path to the same egress router:

	[edit protocols mpls]
	aviva@R1# set label-switched-path R1-to-R5 secondary secondary-path-R1-to-R5 standby
	aviva@R1# set path secondary-path-R1-to-R5

Discussion

When you create a basic LSP on the ingress router, one route is set up to reach the egress router and all the LSP's traffic is forwarded along this route. If a failure occurs along the path—for instance, if a router's interface goes offline, if an entire router goes down, or if the physical link between two routers is cut—the ingress router recalculates the LSP's path and re-establishes the LSP if possible. However, until the ingress route learns of the LSP failure and recalculates a new LSP, all traffic going into the LSP is dropped and never reaches the egress. Depending on the length of the LSP, the speeds of ...

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