Cisco – Using EIGRP to Advertise a VPN Tunnel Route

I would look for an MTU issue.

With an MPLS tunnel the packets must be slightly larger than the payload -- 4 bytes for the MPLS label, for each encapsulation (ie if you're going to put MPLS tunnels into an MPLS tunnel, the outside tunnel will be 8 bytes larger than the payload). Here's a discussion of this.

Hopefully you're not filtering ICMP messages -- if you are you'll be dropping the "use a smaller MTU" packets the network will be sending to your hosts if indeed you are sending too-large packets over the wire. This discusses issues related to MTU...

One thing you can try on your end without involving your ISP is you can shrink your MTU on your border device -- that way it negotiates a proper MTU with your inside network for traffic going over the MPLS link.

I don't think that you will be able to talk your data center provider into sharing an EIGRP ASN, think of them as your ISP and an external network. Also if you have overlapping ip's that could cause an issue especially if you broadcast the wrong network(s) into the ASN.

Now that being said, you are probably getting an Ethernet drop from your data center correct? I don't believe you would see this failure condition (UP/DOWN on one side, UP/UP on the other) with a strait Ethernet drop. The author specifically points out SONET networks - due to link integrity being local on both sides - for doing this. Since link integrity with Ethernet is not local to each side, you would be more likely to see an Up/down & Up/down condition, which would cause both routers to fail over to the secondary links preventing this kind of issue.

BTW: Network Warrior is an excellent book - one of the few tech books i've read cover-to-cover and not just used as a reference.

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Your comment got me thinking, they could have you setup in 1 of 2 ways. The first is actually less likely.

1. You are directly connected to a router - in that case the their router would detect your router going down and adjust accordingly.

2. You are connected to a edge or core switch (most likely) - In this case you are going to have to talk to them to see how they handle fail-over if your link goes down and work from there. Thinking about it a little more, they would have to be running some sort of routing protocol to detect this kind of failure. My guess though is it is more likely to be BGP or OSPF than EIGRP. But in any case they should have a "way they do that" already.