Preface:
Reading through O'Reilly's Network Warrior in the chapter "Ethernet Resiliency he describes the following Scenario (Trying to keep this in the limits of fair use):
alt text http://www.kbrandt.com/files/HSRP_Limitation.png
"Assume that the link between New York
and Los Angeles suffers a partial
outage. Something has happened to
cause the serial interface on
NY-Primary to enter a state of
up/down, but the serial interface on
LA-Primary has stayed up/up. I’ve seen
this more than once on different kinds
of circuits.HSRP responds to the down interface on
the New York side by making the NY-
Backup router active because we’re
tracking the serial interface on
NY-Primary. Packets are forwarded to
NY-Backup, and then across the T1 to
LA-Backup, which forwards them to
their destinations. The return packets
have a problem, though. As the
LA-Primary router does not recognize
the link failure on the primary T1, it
has remained the active router. "
It then goes on to say:
"A more robust solution to a link-failover scenario is to incorporate an interior
gateway protocol running on all of the routers. A protocol like OSPF or EIGRP establishes neighbor adjacencies across links. When a link fails, the routing protocol knows
that the remote neighbor is unavailable, and removes the link from the routing table."
My Situation, and Question:
This seems like what I might be looking for. I will have to links from Datacenter provider and I have to routers I would like to have be redundant. HSRP can help me on the LAN side, but since their routers can't talk to mine, HSRP from them won't help with WAN redundancy because if one of routers fails the provider's won't know about it. Is EIGRP a possible solution in my scenario like the one described (Assuming a EIGRP ASN can be shared between my router and the datacenter, this normal?) ? Can anyone explain how this works with an example, or have a link to something I can read that shows examples of how this works?
In my case, the provider will own the address and not myself, so they advertise them on the internet and have redundant providers for the ip addresses. Also, my goal is failover, not balancing.
Here are some related questions on my recent exploration of network redundancy:
Network Redundancy Example
Getting Started with NIC and Switch Redundancy
Best Answer
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.
Your comment got me thinking, they could have you setup in 1 of 2 ways. The first is actually less likely.
You are directly connected to a router - in that case the their router would detect your router going down and adjust accordingly.
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.