Thursday, March 5, 2009

IE SP Vol2 Lab 4 Task 4

4.1 Complete, no issues
4.2 Complete, no issues
4.3 Complete, no issues. neighbor send-label tells bgp to send the lables.
4.4 and 4.5 Complete--lots of issues!!!

Tasks 4.4 and 4.5 were a major pain. I'm still having a tough time with TE, but I'm getting there slowly but surely. I refused to look up the answers on these tasks and kept pounding away at it until I got it figured out.

Here's a little checklist for getting it setup.

1. Keep in mind that TE tunnles are unidirectional. A tunnel interface does NOT need to exist on both sides, as is common with gre/ipsec tunnels. It is for one-way transfer of traffic. As a matter of fact, by setting up tunnels on both directions, it can exhaust rsvp bandwidth and make bringing up all of the tunnels impossible.

2. mpls traffic-engineering tunnels must be configured globally and at the interface level on all routers in the path, including the head.

3. ip rsvp bandwidth must be reserved on all links in the path, including the head

4. The tunnel must have an ip address (unnumbered is fine), priority, and path configured.

5. If an explicit path is used, all hops must be valid and the correct name or idenitifer must be used.

And here is a list of verification steps:

1. Check sh ip rsvp int on all routers to ensure rsvp is enabled
2. Check sh mpls traf tun on the head to look for error messages and tunnel state
3. Check sh mpls traf top path to see the path the tunnel is taking

For establishing the explicit path, I like to do the following:
1. Configure the tunnel for dynamic
2. Shut down some links to force the tunnel to dynamically take the path you want
3. Configure the explicit-path list to mirror the output of sh mpls traf top path
4. Reconfigure the tunnel with the explicit-path

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