Eigrp Load Balancing

shams_ejaz · ‎11-22-2006

Hello All,

We are planning to do Eigrp load balancing between three locations

Previously we have direct connection between location1 PPP via DDN line T1 128kbps and location2

We are using Cisco 1721 With Eigrp protocol redistribution of Rip V2

Now we want to connect

Location1 to Location2

And Location2 to location3

And location 3 to location1

In triangle shape for the purpose of load balancing and failover because location1 is connected to data center and location 2 is connected to other locations.

Location1 Cisco 1721 Configuration

!

interface FastEthernet0

ip address 192.168.100.101 255.255.252.0

speed auto

!

Interface Serial 0

Bandwidth 128

Ip address 192.168.50.253 255.255.255.248

Encapsulation ppp

Description Connected to location 2

!

Interface Serial 1

Bandwidth 128

Ip address 192.168.60.253 255.255.255.248

Encapsulation ppp

Description Connected to location 3

!

Router eigrp 1

Network 192.168.100.0

Network 192.168.50.0

Network 192.168.60.0

No auto-summary

No eigrp log-neighbor-changes

!

ip classless

Location2 Cisco 1721 Configuration

interface FastEthernet0

ip address 192.168.50.1 255.255.255.128

speed auto

!

Interface Serial 0

Bandwidth 128

Ip address 192.168.50.254 255.255.255.248

Encapsulation ppp

Description Connected to location1

!

Interface Serial 1

Bandwidth 128

Ip address 192.168.60.252 255.255.255.248

Encapsulation ppp

Description Connected to location 3

!

Router eigrp 1

Network 192.168.100.0

Network 192.168.50.0

Network 192.168.60.0

No auto-summary

No eigrp log-neighbor-changes

!

ip classless

Location3 Cisco 1721 Configuration

interface FastEthernet0

ip address 192.168.60.1 255.255.255.128

speed auto

!

Interface Serial 0

Bandwidth 128

Ip address 192.168.60.254 255.255.255.248

Encapsulation ppp

Description Connected to location

!

Interface Serial 1

Bandwidth 128

Ip address 192.168.50.252 255.255.255.248

Encapsulation ppp

Description Connected to location 3

!

Router eigrp 1

Network 192.168.100.0

Network 192.168.50.0

Network 192.168.60.0

No auto-summary

No eigrp log-neighbor-changes

!

ip classless

All these links will be DDN line T1 128kbps

How does this can work and what will be router configuration to make load balancing

As I know that eigrp can do unequle cost load balancing. so Please me help

As I do not have the links online so I cannot do testing

Thanks,

Shams

zubairjalal · ‎11-22-2006

Hi.

You need to give the variance command under Router eigrp 1.

It should be like this.

Router eigrp 1

variance 20

Network 192.168.100.0

Network 192.168.50.0

Network 192.168.60.0

--Pls rate if this helps--

alsayed · ‎11-24-2006

Hi

Kindly;i have to know why u have using variance command under the eigrp & why u have give 20 for the variance

10xs

amit-singh · ‎11-25-2006

Hi,

By-default EIGRP does equal-cost path load-balancing upto 4 equal cost paths. Here in this case if you dont use "maximum-paths" command under the EIGRP configuration it will take only one path into account. If you want EIGRP to do equal cost-path load-balancing you can use maximu-paths command to set the paths to it.

We use " Varience " command under the EIGRP process to make it do the un-equal cost path load-balancing. When we have the varience factor under the EIGRP process like "20 " in this case, the feasible distance or the metric will be multiplied with the varience factor. The paths/routes with the metric less than resulted value of the above calculation will all become eligible to forward the packets to the destination using the different un-equal cost path routes.

The fesaibility condition should be met in order to do the equal-path load-balancing.

HTH,

-amit singh

devang_etcom · ‎11-26-2006

hi ali,

variance command will halp you to include the number of available path to the same destination in to the routing table... here is the good example of the variance...

lets assume that you have various path with the cost of 2,4,7 and 9. (this cost vlaues are just for simplified the explanation) now as per the rule routing table include only the best path in routing table it means only the lowest cost path towards the destination will appear in to the routing table... so here path with the cost of 2 is the lowest cost path towards the destination so there will be only the path with cost of 2 will appear in the routing table... here you have various cost path connecected to the destination but because of limitation you will utilize only single path which is best path... but now you want to go for the loadbalancing or you can say you want to utilize your all the path... now variance come into the picture... now i will explain you the variance with different vlue so you will have proper idea of the VARIANCE command...

VARIANCE with the value of 3...

here first of all take lower cost path...

here in our case lower cost path is 2...

now multiply lower cost path with the variance vlaue which we are going to use in this case variance is 3... therefor 2x3=6

now this six indicate that path with the cost 6 or less then cost 6 only will appear in to the routing table... so now we have two path with the cost less then 6...and they are path with cost 2 and 4

if you use variance with the value 3... then only path with the cost of 2 and 4 will apear in the routing table...

VARIANCE with the value of 4...

total number of path in routing table= lowest cost x variance... here 2x4=8

here we have three path whose cost is less then 8 and they are 2,4 and 7...

now here we have three path in routing table in order to loadbalance... whereas in early case we have only two path for loadbalancing in routing table...

if you use variance with the value 4... then only path with the cost of 2,4 and 7 will apear in the routing table...

now Variance with value 5...

total number of path in routing table= lowest cost x variance

here we have 2x5=10 so now we have all four path with cost 2,4,7 and 9 will appear in routing table and we can have load balancing on all four path...

so just remember that variance is the value which is multiply with the lowest past cost availalbe among the multiple path... and routing table include only the path wich the cost wichi is equal to or less then the multiplication of the variance and lowest cost path...

hope this will help you to clear the idea of variance...

rate this post if it helps

regards

Devang