Just like OSPF or RIP, EIGRP can do load balancing but it has one more trick in its hat. RIP and OSPF both can do load-balancing but the paths have to be equal.
EIGRP can do something cool…unequal load-balancing! Even better it will share traffic in a proportional way, if you have a feasible successor that has a feasible distance which is 5 times worse than the successor then traffic will be shared in a 5:1 way.
Let’s take a look at an example of how EIGRP can do load balancing:
We’ll view this topology from R1’s perspective. Let’s fill in the successor, feasible successor, advertised and feasible distance in a table. If you have no idea how this works please read my introduction to EIGRP first.
|
Advertised Distance |
Feasible distance |
|
|
| R2 |
15 |
20 |
|
| R3 |
10 |
15 |
SUCCESSOR |
| R4 |
14 |
114 |
FEASIBLE SUCCESSOR |
This is our first example where we found out the successor and feasible successor. If you look at the routing table you will only find the successor there. Now we are going to change things so we’ll see the feasible successor in the routing table as well so it will load-balance.
You can do this by using the variance command. The variance command works as a multiplier:
Hi Rene,
If we have three path to destination and we configure variance to use the three path just like in your example here :-
https://networklessons.com/eigrp/eigrp-variance-command-example/
My question is :-
The traffic will be shared in which way ? to be more clarify, In the begging of this article you said " if the feasible successor has a feasible distance which is 5 times worse than the successor then traffic will be shared in a 5:1 way " so what the rate will be if we have three path to destination ( the successor and tow feasible successors ) ?
i didn’t understand this
... Continue reading in our forumcould you explain more details about this . that will be hard when the numbers are high .
and i show command its show me share count
Hello Florain
The FS is a FS only if it is not in the routing table. If it is in the routing table it has the best metric and is thus considered a successor, even if there are more than one such as is the case with EIGRP load balancing.
... Continue reading in our forumHello Marcel
All routes learned via EIGRP are contained within the topology table, whether they are actively being used (in the routing table) or not. These routes are examined by EIGRP and only the route with the best metric is placed within the routing table. The rest of the routes still exist in the topology table however.
So, the routing table will only have a single route to a particular destination by default (unless two routes have an equal metric of course). In order to determine if a route can be used for unequal load balancing, the variance value i
... Continue reading in our forum@shashank.mohan89 Thanks for sharing this, it’s indeed less or equal. And @lagapides, thanks for labbing this up
I just fixed it 
Rene