Setting load balancing using EIGRP - Link-loss detection

Posted on 2009-12-21
Medium Priority
Last Modified: 2012-06-27
I am designing a solution for load balancing.  I have two routers to two separate ISP's.  I have set up 2 static routes in EIGRP to to the next hope addresses which are the routers (see config).  I have configured variance with a multiplier of 2.  The firewall interfaces are not running EIGRP.  Now that I have this on paper I am seeing quite a few design issues.

Q: If there is a link loss to the ISP, how will the router (my 6513 super mod) know to remove the failed route from the routing table?   Presumably therw could be a failure on the outside firewall interface and since that is not part of the EIGRP process (hello's etc.) how will the router (6513) know to stop sending packets that way?

router eigrp 1
 variance 2
 redistribute static
ip route
ip route

S* [1/0] via
               [1/0] via

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Question by:every1isevil2
  • 3

Expert Comment

ID: 26096848
You would have to run some type of routing protocol with the ISP routers or with your firewall for this to work.  You are correct in that it would never detect if a link was down in between the firewall and the ISP routers if you just use static routes on the 6513 switch.  

Expert Comment

ID: 26096980
How are the firewalls learning routes?  Is it just a static default routes to the ISP routers?  Does the ISP offer routing protocols?  Basically what you have to do is get the 6513 Switch to learn the default routes some how from the firewall or the ISP routers.  If the 6513 Switch learns the default route via a protocol then once it loses it, it'll just send it out the other link.  Make sense?

Author Comment

ID: 26097180
I do not believe the ISP offers this.

The firewall are NAT firewalls and yes they are static route.

As far you as you know, with the exception of the link loss detection, EIGRP will still load balance though? Right?

Accepted Solution

itszasecret earned 2000 total points
ID: 26097480
Yes it should load balance them with the "variance" command.  I forgot that there may be a way to use Object Tracking to remove the one static route out of the routing table without using a protocol.  Here is a link... this should work for you but I've never actually implemented this...

LVL 50

Expert Comment

by:Don Johnston
ID: 26098894
>If there is a link loss to the ISP, how will the router (my 6513 super mod) know to remove the failed route from the routing table?

If the link loss is detectable (interface down or line protocol down), then any routes which use that link will be removed from the routing table. That router will then advertise those paths as invalid (down).

If the link loss is not detectable, there will be no change in the routing table.

In that situation, Object Tracking is used.


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