Load sharing across unequal wan links

[psalada]

We have two wan links of 512kbps and 256kbps. We are running EIGRP. The data is running at 90% saturation on the 512kbps link and NOTHING across the 265kbps link.

I have asked our management team to apply variance and traffic sharing to make packets flow on both links. We have a 7200 router with IOS (tm) 7200 Software (C7200-JS-M), Version 11.2(26)P4, RELEASE SOFTWARE (fc1).

I have been told that the links have to be the same. I think that this is nonsense and variance will work.

I need someone at CISCO to tell me if I am in error and if so, How do I fix this?

[giedriusa]

Hi,

under interface configuration, configure bandwith 512 and bandwith 256 as appropriate fot a particular interface on both routers and under EIGRP configuration use a command variance 2. Also, You might need a command maximum-paths 6 under eigrp configuration.

I am positive this works with IOS 12.0 - 12.2, but not sure about IOS 11.2, so an upgrade to later IOS might be needed.

HTH

Regards

Giedrius

[psalada]

Dear Giedrius,

Thank You for answering. I will inform my team that this will work. IOS 11.2 will work as well.

This is a very old problem that CISCO addressed years ago when routing was introduced.

If you have any other methods tha would work better please let me know.

[rsissons]

The router will load share with the variance option but be aware that it will be at the session level, rather than on a per packet basis, so, depending on your traffic, you may not see the utilisations you expect. With unequal bandwidth, this will mean some sessions are established over the highr speed link while some take the slower for all their traffic.

It is possible to load share on a per packet basis by disabling fast switching, 'no ip route-cache' on the interface, but this is not recommended as it will severely impact the performance of the router and, with unequal bandwidth, some frames will arrive out of sequence and require resequencing which will effectively throttle all the traffic to the lower speed link.

[psalada]

Thank you. I really appreciate the information.

Can you route the traffic depending on a type of packet ?

Could I make certain web traffic flow down the slower pipe ?

[loma]

hi,

You can use policy routing to send www traffic over the 256k line