EIGRP equal cost load balancing

rramlal · ‎04-09-2015

Hi All,

I am trying to configure equal cost load balancing on a remote site that connects to the head office using a Cisco 2901 router. This router connects to two WAN links which has the same bandwidth. I connected both of them and hard set the bandwidth levels on the interfaces however the composite delays are different which makes one be preferred over the other.

How can I get these links to load balance? Is there a command on eigrp that would allow this to happen?

Thanks

Jon Marshall · ‎04-09-2015

Do you know why the composite metrics are working out differently ?

What is the WAN and where are the routes coming from in terms of devices at the HO site ?

You can always try playing with delay on one of the router interfaces to try and balance out the metrics or more likely use an offset list inbound on one of the routers to match up the metrics but first I would try and find out why they are not the same.

EIGRP can load balance over unequal cost links but you don't really want this if the bandwidth is the same on both links.

An alternative if this site only talks to the HO site is to configure two default routes rather than use EIGRP but I suspect you don't want to do this.

So what does the WAN consist of between HO and this site ?

Jon

Richard Burts · ‎04-09-2015

It would be helpful to know what interfaces you are using on the 2901. Would you post the output of show interface for these interfaces? It might also help us understand the issue if you would post the configuration of EIGRP.

HTH

Rick

HTH

Rick

rramlal · ‎04-27-2015

Hi All,

First of all, thanks for responding so promptly to my question. We recently changed out the head office router from a Cisco 3660 to a Cisco 3945 and surprising after that all the remote sites showed equal cost load balancing to the site.

This WAN topology consists of two WAN clouds, lets say WAN A provider and WAN B provider. The remote sites all connect to this cloud at 2MB for both WAN A and B but the head office connects to cloud for WAN A (25MB) and WAN B(10MB).

My questions are as follows:

1. How do I verify the bandwidth of the WAN links apart from what the provider is showing me for the head office? If we do a file transfer to the remote sites, it will be limited to the bandwidth allocated for the remote site. For instance transferring to remote site A will be a maximum of 2MB.

2. I would like to set up un-equal load balancing from the head office to other remote sites in the ratio of 2:1. Do you see any issues here?

I have attached some configs for a remote site and the head office.

paul driver · ‎04-10-2015

Hello

it sounds like you have unequal eigrp,paths!

Even though you have specified the same BW the delay values on the wan link paths are different and as by default eigrp uses the lowest BW and cumulative delay on the paths for composite metric calculation

sh ip eigrp topology x.x.x.x/yy

This will show you the current eigrp BW/delay and compsitic metrics values of each prefix

Another way to negate delay is to change the eigrp weight metric so only BW is used for calculation but I doubt if these peers are between a ISP you would and should not do this!

Example;

router eigrp xxx

metric weight 0 1 0 0 0 0

as for unequal Eigrp LB

1)

divide the two composite metric values of a path ( rounding the value up to the nearest whole number)

2)

then use use that number as a variance in the eigrp process

3)

router eigrp xxx

varience x

res

Paul

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Kind Regards
Paul

Alex Pfeil · ‎06-20-2018

It is also possible to modify the delay so the routes show up as equal. There are different posts on how to do this.

Thanks,

Alex