EIGRP Load-Balancing

Unanswered Question
Aug 14th, 2009

Hi there,

Given:

Two giglinks

Two ds3 links

vlan x,y,z are via two giglinks as primary path and backup ds3's if both giglinks fails.

vlan a,b,c are via two ds3's and backup giglinks if both ds3's fail.

Tweaking the metric, delay or applying variance is i'm thinking. No PBR if possible. All EIGRP load-balancing only. Just trying to find how can I set preferred routes to a destination address using EIGRP with single AS.

If it's not possible, floating static routes with tracking is my last resort pointing to the next hop with a lower metric or AD than 90.

Thanks in advance...

Gerard

I have this problem too.
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Mohamed Sobair Sat, 08/15/2009 - 00:35

Hi,

Its possible if the vlan a,b,c and vlan x,y,z are learned via EIGRP.

If its learned via eigrp, then the appropriate way is to use the (Offset-list) command.

The (offset-list) command is a mechanism to increase the delay of networks in both direction in OR out tp prefer a path over another.

In your case, you would increase the delay of routes for incomigly traffic on non desired path for that destination.

On the other hand, the (Variance) is a multiplier. you would only use the variance command if you want to loadbalance traffic across un-equal cost paths.

consider you have a Network x with 3 possible paths and their metrics are:

1- 2

2- 4

3- 6

To reach Network x,Eigrp will choose path 1 with a metric of 2 by default, if you want Eigrp to use path2,

you will set the variance to 2, likewise , if you want to use path 3 , you will set the variance to 3.

because (lowest metric * variance) > metric of path to be included

please refer to the links bellow for more information:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_cfg_eigrp.html

Regards,

Mohamed

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