Interesting EIGRP Scenario

Well members I've been stumping my way through a scenario that has been
driving me nuts all afternoon.

MPLS cloud and Tunnel cloud .

I had a route that was getting advertised as an internal eigrp network of
10.2.4.0/24 over the tunnel preferred route R3. The network was also learned
over the MPLS BGP neighbor on a different router R1 and redistributed into
eigrp. R2 would learn the route from R3 as eigrp internal and from R1 as
eigrp external. R1 R2 and R3 are connected in a triangle.

ROUGH TOPOLOGY:
      /--------------10.1.4.0/24------------\
    / \
Tunnel R3-gig-R2-gig-R1 MPLS AS200
                   \--fastE----/

If R3 ever hiccupped and the Tunnel was down a loop would occur. After the
tunnel came back up, eigrp would show that R1 advertized the network to R2 as
Eigrp internal, that R2 advertized the network as eigrp internal on R3, and
that R3 advertized the network to R1 as eigrp internal.

The weird thing is the route now shows a tag of 200 after the tunnel came back
up. I could shut this tunnel down again and it would still show everything as
eigrp internal instead of being advertised as external from BGP to EIGRP on
R1.

I've got a temporary solution of kicking the Delay way up on the Fast E
between the R3 and R1 but I'm a bit baffled at this point why or what process
is going on that would keep the network advertised as eigrp internal and then
tag it with 200 off the external redistributable route from BGP

Patrick Laidlaw - Deployment Engineer
E: patrick.laidlaw_at_wwt.com<mailto:patrick.laidlaw_at_wwt.com>

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Received on Mon Jun 13 2011 - 19:37:14 ART