Solved

EIGRP problem

Posted on 2011-03-17
11
458 Views
Last Modified: 2012-05-11
At work I look after 4 data centres, with a router utilizing 4/4 IPMAN cross connects. Each of these routers has atleast one link to this IPMAN, over which we run EIGRP as the IGP.

Now everything had been working fine till a few months ago, when one of the links, connecting Colo B ---- Colo C went down. I noticed the EIGRP neighbor relationship was no longer forming on Colo C side (nothing in the debugs) and on Colo B side the neighbor as Colo C would show up, RTO would expire, and it would go down/up again. We tried everything (link speeds, duplexes, EIGRP statements, no static routes) - but resigned it as a hardware/link fault which we would need to chase up with the IPMAN provider.

A few months down the line, everything was working fine but yesterday the neighbor relationship between Colo B ---- Colo D went down. The issue was exactly the same, this time no debugs or neighbors (with Colo D) showing up on Colo B , and Colo D keeps trying to form a relationship with Colo B, times out, and starts over again.

This is pretty strange and since Colo B --- Colo D link is critical for business operation, I am keen to figure out the cause of this.  Currently i'm routing the traffic through another router with static routes and all is well, but would love some feedback to see what your opinions are. Is it a link fault? Is there anything I could do to confirm this?

There are no CRC/errors on the actual interfaces, the routers are all fine with rest of the links working well. No duplex/speed issues as this was working well just yesterday.

Appreciate all the comments guys.
0
Comment
Question by:demon777
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
11 Comments
 
LVL 5

Expert Comment

by:shubhanshu_jaiswal
ID: 35165056
It is very hard to visualize the topology from the written description..could you please post a diagram which will show all the routers involve in the EIGRP Process...
0
 
LVL 6

Expert Comment

by:602650528
ID: 35166001
Hi demon777,

Eigrp is very finicky about MTU size and the problem doesn't show up immediately. I strongly suspect this issue has to do with different mtu size on the interface of the eigrp neigbours. Can you check the mtu size and make sure they are same across a link between neigbours.
0
 
LVL 18

Expert Comment

by:decoleur
ID: 35166232
what do the debugs show you during these failures? capture them from both sides with a common time source and see if that doesn't help.

-t
0
Are You Headed to Black Hat USA 2017?

Getting ready for Black Hat next week? Kick things off with the WatchGuard Badge Challenge and test your puzzle and cipher skills. Do you have what it takes to earn our limited edition Firebox Badge? Get started today - https://crimsonthorn.net

 
LVL 17

Expert Comment

by:rochey2009
ID: 35166922
It looks like a service provider problem.

Can you ping from one end of the link to the other?
0
 
LVL 28

Expert Comment

by:mikebernhardt
ID: 35166953
Colo B has no debugs at all? There's got to be something, unless the appropriate interface is not part of the EIGRP process anymore. If you can post the EIGRP config and the appropriate interface config from both sides, that would help.
0
 
LVL 28

Expert Comment

by:mikebernhardt
ID: 35166970
Also, remember that in a multipoint configuration on subinterfaces (if you have that), you may need to enter neighbor statements since multicast doesn't work well.
0
 
LVL 28

Expert Comment

by:asavener
ID: 35167775
I've seen EIGRP fail to establish neighbor relationships dynamically, but adding neighbor statements will cause the relationship to start working.

Have you tried adding static neighbor statements?
0
 
LVL 24

Expert Comment

by:rfc1180
ID: 35172665
If you seriously want help with the issue you are going to have to post your configs and provide a detailed network diagram. It is really hard to comment on your issue as what you are experiencing could be related to just about anything. If you cannot provide this information, I would then recommend that you hire a engineer in your local area that can assist, what you describe can be a lengthy process to diagnose the issue.

Billy
0
 
LVL 1

Accepted Solution

by:
demon777 earned 0 total points
ID: 35228279
Sorry to update this late guys, unfortunately none of the answers were correct.
The router dropped two more neighbours and had to be finally rebooted, and all neighbours came back online. It was indeed a hardware issue and we will be looking at replacing this router sometime in the future.

We've had MTU issues in the network and all interfaces operate on a standardized size. Static neighbour statements were not an issue as other neighbours in the same range were forming a relationship fine, over the same common IPMAN link.

Debugs on the other end showed nothing (yes, nothing!) which was what was weird about the whole thing - well its all good now thank you for the answers.
0
 
LVL 28

Expert Comment

by:mikebernhardt
ID: 35243349
Most likely it's not a hardware issue, but an IOS software issue. You might look into upgrading the software with the latest maintenance release.
0
 
LVL 1

Author Closing Comment

by:demon777
ID: 35292532
None of the answers stated were correct.
0

Featured Post

Ready to trade in that old firewall?

Whether you need to trade-up to a shiny new Firebox or just ready to upgrade from whatever appliance you're using now, WatchGuard has the right appliance for you! Find your perfect Firebox today with appliance sizing tool!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In the hope of saving someone else's sanity... About a year ago we bought a Cisco 1921 router with two ADSL/VDSL EHWIC cards to load balance local network traffic over the two broadband lines we have, but we couldn't get the routing to work consi…
Quality of Service (QoS) options are nearly endless when it comes to networks today. This article is merely one example of how it can be handled in a hub-n-spoke design using a 3-tier configuration.
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
Monitoring a network: why having a policy is the best policy? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the enormous benefits of having a policy-based approach when monitoring medium and large networks. Software utilized in this v…
Suggested Courses
Course of the Month10 days, 13 hours left to enroll

628 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question