[c-nsp] MPLS TE auto-tunnel and ISIS metric

Peter Rathlev peter at rathlev.dk
Wed Oct 16 03:40:14 EDT 2013

On Tue, 2013-10-15 at 17:29 -0600, dip wrote:
> you should be able to see the configs with the help of "show derived
> config interface Tu65336"

Ooh, I didn't know that command. Very nice. :-)

    interface Tunnel65336
     ip unnumbered Loopback0
     no ip redirects
     no logging event link-status
     mpls ip
     tunnel mode mpls traffic-eng
     tunnel destination
     tunnel mpls traffic-eng autoroute announce
     tunnel mpls traffic-eng path-option 1 explicit name __dynamic_tunnel65336
     tunnel mpls traffic-eng fast-reroute
     no routing dynamic

> , one thing you would notice is that they
> are created with explicit path option not dynamic path option  and
> thats why you see that  its not following shortest path based on your
> IGP metric.Though it will detect that there is a better path


    dist-1#sh ip explicit-paths name __dynamic_tunnel65336
    PATH __dynamic_tunnel65336 (strict source route, path complete, generation 58, status non-configured)
        1: next-address
    dist-1#show ip route
    Routing entry for
      Known via "connected", distance 0, metric 0 (connected)
      Routing Descriptor Blocks:
      * directly connected, via TenGigabitEthernet5/4
          Route metric is 0, traffic share count is 1

Strangely (to me at least) is that the explicit path "next-address" is
actually the local address of the (wrong) interface, not the remote

    dist-1#show ip interface brief Te5/4
    Interface              IP-Address      OK? Method Status                Protocol
    TenGigabitEthernet5/4  YES NVRAM  up                    up      

I still don't understand why it would select this path and not the one
with the lowest cost.

>  ..So if
> you do "show mpls traffic-eng tunnels tunnel XYZ" , it should tell you
> the shortest unconstrained Path which is probably what you want it to
> follow .

It does exactly tell my that. Is there any way to make it use this? :-)


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