EIGRP load balancing

[john-lam]

Need some ideas on how to load balancing setup.    I have 2 routers, each with a layer GE WAN connection and receives eigrp routes.  The routers also have a layer 3 connection between them and are exchanging eigrp.  

I want to have traffic reach router 1 and goes out on the wan link on that router.  I also want router 1 to send some of that traffic to router 2 so that both wan circuit would be used instead of sitting idle.   Metrics  on routes received from  from router 2 are a little higher because of the interconnecting layer 3 link and never get put into the routing table.    I tried using the variance command, played with offset, load, delays and was able to equalized the metrics between the 2 sources andhave both paths into the routing table.  But can't get it to work on router2 since the metrics was increased due to the metric manipulation that I did on router 1 had affected the routes learned.  

Thanks 

so no matter what I do, the routes coming from the other routers would always be a little bit higher than the routes learned from the WAN link.   

Any ideas on how I can get the router to 'ignore' the increase in metric being learned from the interlink?

[Seth Beauchamp]

I would think you could use an offset list on router 1 in increase the metric of some subnets so that metrics are better from router 2. How did you have this configured?

Are you getting a default route from these WAN connections? If so, you could filter out (distribute-list) some prefixes on each WAN link, allowing a default route to take over if one became unavailable.

If you have control over the other side of the WAN, you could possibly summarize some of the routes on one of them so that the other receives more specific routes.

What does the LAN side look like? If you have multiple subnets using HSRP between the two routers for the gateways you can make one router active for some subnets, and the other router active for other subnets so that some subnets use router 1 as the gateway and some use router 2 as the gateway and route according to the local routing table on each router.

[john-lam]

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@Seth Beauchamp wrote:
I would think you could use an offset list on router 1 in increase the metric of some subnets so that metrics are better from router 2. How did you have this configured?

Are you getting a default route from these WAN connections? If so, you could filter out (distribute-list) some prefixes on each WAN link, allowing a default route to take over if one became unavailable.

If you have control over the other side of the WAN, you could possibly summarize some of the routes on one of them so that the other receives more specific routes.

What does the LAN side look like? If you have multiple subnets using HSRP between the two routers for the gateways you can make one router active for some subnets, and the other router active for other subnets so that some subnets use router 1 as the gateway and some use router 2 as the gateway and route according to the local routing table on each router.

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I have tried using offset to increase the metrics from the WAN link by the metric increased with the extra hop.  That get 1 router to work. But as the router passes that route over to the router, the metric caused 2nd router to not have equal cost paths.    

Would be easy if I have controller over the up stream router but I don't.  As far as the lan side is concern, I have tried HSRP, GLBP.   

[john-lam]

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@Seth Beauchamp wrote:
I would think you could use an offset list on router 1 in increase the metric of some subnets so that metrics are better from router 2. How did you have this configured?

Are you getting a default route from these WAN connections? If so, you could filter out (distribute-list) some prefixes on each WAN link, allowing a default route to take over if one became unavailable.

If you have control over the other side of the WAN, you could possibly summarize some of the routes on one of them so that the other receives more specific routes.

What does the LAN side look like? If you have multiple subnets using HSRP between the two routers for the gateways you can make one router active for some subnets, and the other router active for other subnets so that some subnets use router 1 as the gateway and some use router 2 as the gateway and route according to the local routing table on each router.

---

I have tried using offset to increase the metrics from the WAN link by the metric increased with the extra hop.  That get 1 router to work. But as the router passes that route over to the router, the metric caused 2nd router to not have equal cost paths.    

Would be easy if I have controller over the up stream router but I don't.  As far as the lan side is concern, I have tried HSRP, GLBP.   

[Seth Beauchamp]

Sounds like you were trying to do ECMP with the offset list, that probably isn't going to work. Config example for what im suggesting below. The idea is to prefer one router for certain subnets, and the other router for other subnets. Its not going to give you perfect load balancing though. I would also agree with Joseph about avoiding variance.

Router 1:
access-list 1 permit 10.1.2.0 0.0.0.255

router eigrp 1
offset-list 1 in 200 GigabitEthernet1

Router 2:

access-list 2 permit 10.1.5.0 0.0.0.255

router eigrp 1
offset-list 2 in 200 GigabitEthernet1

Subnet 10.1.2.0/24 should be preferred on R2 while 10.1.5.0 is preferred on R1.

[Joseph W. Doherty]

BTW, one of our original hall-of-fame-members very much recommended against using EIGRP variable load balancing.

If you're routers can support it, you might look into Cisco's PfR technology (which can dynamically load balance).