EIGRP Unequal cost load balancing

[ali007]

Hi,

I have two layer 3 switches and each have a WAN connection connected. currently each switch is using the direct WAN connection as primary so I thought I will use variance 2 so that each switch can use both links. however, after applying variance it still uses the direct link only.

upon checking I have realised that both switchesEIGRP is not seelting a feasible successor as the reported distance for the secondary link is equal to the Feasible distance of the primary but I believe it should be less than the primary.

when I type

show ip eigrp topology

it only shows a single link e.g. :

P 0.0.0.0/0, 1 successors, FD is 256028160
via 10.150.16.1 (256028160/256000000), GigabitEthernet1/0/1

but if I type in

show ip eigrp topology

all I see both links e.g.:

P 0.0.0.0/0, 1 successors, FD is 256028160, serno 82
via 10.150.16.1 (256028160/256000000), GigabitEthernet1/0/1
via 10.150.1.1 (256028416/256028160), Vlan100

vlan 100 has delay of 10 and bandwidth of 1000000

while gi1/0/1 has a delay of 100 and bandwidth of 100000

can anyone help me with this?

thanks.

[David Ruess]

Hello,

It looks like the RD of the FS route is equal to the FD of the Successor route. I believe it needs to be lower. Can you lower the Delay of VLAN 100 to a delay of 9 to lower the FS RD below the Successors FD and see if that resolves the issue?

-David

[ali007]

HI David,

thanks for the response. I don;t think I can reduce the delay as its already set to 10micro seconds i.e. the minimum it can go.

unless you know how to?

Regards

[David Ruess]

Whoops I think you're right. My mistake. Then you can increase the Gig interface to be more delay. Just to increase it slightly.

You could also apply an offset list to the incoming routes from the primary connection to add to its current metric to make it a bit higher.

-David

[ali007]

thanks David.

do you have an example of the offset list?I did study it one many years ago but would be nice to have a working sample configuration.

kind regards 

[David Ruess · Accepted solution]

Of course.

Enter your eigrp AS mode and you can configure it there. Or if using Named mode it would be under topology base. But the config is the same.

router eigrp <AS#>

offset-list 0 in 100 g1/0/1

or

router eigrp <name>

address-family ipv4 unicast autonomous-system <AS#>

topology base

offset-list 0 in 100 g1/0/1

This command will add 100 to the metric to all incoming routes on that interface. (That's from the "0" in the command. It means all without specifying an ACL) you shouldn't have to add much metric thats why I only put 100 on there. Let me know if that works.

-David

[MHM Cisco World]

Please share config here, i will analysis it.

[paul driver]

Hello
try a varience on 1 and post the output of:

sh ip eigrp topology 0.0.0.0/0
sh ip route 0.0.0.0

[ali007]

HI all,

thank you for your response but the using the offset resolved our issue. much appreciated.

[MHM Cisco World]

BTW I do small LAB but not finish Yet,
three router connect in triangle design, 
one router must learn prefix from the two other neighbor, but the router only prefer the direct the neighbor connect, I change the variance many times but I could not find result, so I will start hop tonight find why that happened.
for all if I get something I will update.

[MHM Cisco World]