Discussion on Eigrp Load Balancing

[Chandhuru sekaran marimuthu]

Hello All,

Happy new year to everyone!!!

We have two WAN links Primary with 40 Mbps and Secondary with 10 Mbps link. 

Both routers are connected to Core switch, single core switch.

There is a EIGRP between these three devices. In Core switch, we have used one L3 VLAN. Same VLAN used in Routers connected  interface as L2 VLAN. 

So EIGRP neighbor forming between two routers on same interface as L3 VLAN

Hence we could see 2 Successor. And traffic is load balancing, sometime traffic takes secondary and it is 10 Mbps link. So users complaining slowness. 

If it is two Physical interface then we can configure Delay and make primary as metric value. but in this case how can we achieve Primary Router as Successor and Secondary router as Feasible successor?

Please help me on this. Thanks!!!

[Georg Pauwen]

Hello,

that leaves the last option: change the delay on the link that physically connects the core switch to the 10Mbps WAN router, e.g.:

Core Switch

interface GigabitEthernet0/1

description Uplink to 10Mbps WAN router

--> delay 1000

[Chandhuru sekaran marimuthu]

Hello George,

I have tried it. There is no change in metric value since it is L2 interface. 

[Georg Pauwen]

Hello,

is it an option to get rid of EIGRP on the Core Switch altogether ? If it is, you could use multiple static default routes to send traffic at a 4:1 ratio, which would actually leverage what you have, which is a second link (the 10Mbps link) that would otherwise go unused.

Here is how it works:

Let's say, the below are the IP addresses:

IWAN Router 1 (40Mbps Link)
IP address 192.168.13.2

WAN Router 2 (10Mbps Link)
IP address 192.168.13.3

First, you create routes to dummy IP addresses (make sure those don't exist anywhere in your network), with the respective WAN router IP address as the next hop:

ip route 10.0.1.1 255.255.255.255 192.168.13.2
ip route 10.0.1.2 255.255.255.255 192.168.13.2
ip route 10.0.1.3 255.255.255.255 192.168.13.2
ip route 10.0.1.4 255.255.255.255 192.168.13.2
ip route 10.0.2.1 255.255.255.255 192.168.13.3

Then, enter multiple static routes. Traffic will be sent at a 4:1 ratio:

ip route 0.0.0.0 0.0.0.0 10.0.1.1
ip route 0.0.0.0 0.0.0.0 10.0.1.2
ip route 0.0.0.0 0.0.0.0 10.0.1.3
ip route 0.0.0.0 0.0.0.0 10.0.1.4
ip route 0.0.0.0 0.0.0.0 10.0.2.1

[paul driver]

Hello @Georg Pauwen 

I would say there is no need to perform any kind of Load Balancing with static routing , if the OP wanted unequal load balancing then this can be accomplish relative easy with eigrp metric delay recalculation and variance.

[Georg Pauwen]

OP has no access to the WAN routers. That is why the offset list doesn't work, and the metric neither.

[Chandhuru sekaran marimuthu]

Hello Georg,

Instead of getting rid of EIGRP.

We can accomplish in EIGRP by configuring two L3 interface with two different /30 subnet in Core Switch for those two WAN routers connecting interfaces and configuring delay on 10Mbps WAN router interface in core switch to get it success right?

[Georg Pauwen]

Hello,

I guess that would work. Once you have the layer 3 interfaces, you can apply the 'delay'.

[Chandhuru sekaran marimuthu]

Thanks for your valuable time!!!

[paul driver]

Hello

Why are you applying it to the 10mb link and on the l3 switch ?
FYI - You don't change the delay value on the l3 switch you change the delay on one of the WAN rtrs interface facing the L3 switch-  Do this and test again.

Also as i stated in my last post  you can also redistribute changing the eigrp K values in particularly the route delay as i shown in my previous post, Again ths is done on the WAN RTR, However but before you do this can you post the configurations of the two wan rtr and the l3 switch into a file and attach to your OP

[Chandhuru sekaran marimuthu]

Hello Paul,

As i stated earlier, there is no scope/no access for us on those two WAN routers. So am trying to accomplish from Core Switch end itself.

[paul driver]

Hello
Okay I missed that part so apologies to all.

So before you make any other changes, can you post a topology diagram of your network and the output of the below into a file and attach to your OP

sh ip eigrp topology
sh ip route

[Chandhuru sekaran marimuthu]

Hello Paul,

Please find the attached file for your reference, 

[paul driver]

Hello

Have you tried to liaise with your ISP and ask them if they could advertise the prefixes from the 50mb circuit with a better metric than the 10mb circuit, or even for them to offest the 10mb circuit link to be less preferred?

[Chandhuru sekaran marimuthu]

Hello Paul,

We can do that. Lets try that option if there is no option from Core switch.

I thought of doing something from Core Switch itself, thats why created this discussion.

If there is no option, then i will take necessary step with ISP to make those Changes.

Am really thankful to all three of you @paul driver @Georg Pauwen @_|brt.drml|_ .

Thanks again for spending your valuable time and explained me a lot. 

[paul driver]

Hello

iam not saying you dont have options from the core perspective but the most simplistic solution i would say would be for the isp to make the necessary changes especially as it the same isp managing  both circuits