load balance between links

[arvenugopal]

i have a query how to do a load balance and fall back with when wan link fails.in a given scenario like this.

serial link 256 ISP1 serial link 256 ISP2

| |

router1 router2

================

|l3 swich

=================================

+++ +++ +++ +++

access switch

1) 50% of users in ISP1, rest in another ISP

2) if router 1 link fails. has to fall back to second link. and vice versa

)

[c.crocker · Accepted solution]

One option is two HSRP groups on the routers. RTR1 Primary for group 1 and RTR2 primary for group 2. This would require assigning two static default routes on your layer 3 switch.

Another option is running an IGP such as OSPF between the routers and the layer 3 switch. The routers could advertise default to the switch. The switch will place two equal cost OSPF default routes in the table.

The load-balancing in these scenarios would depend on the source-destination pair in the switches layer 2 tables.

I would also recommend adding an additional layer 3 switch and run HSRP. Reduce the single points of failure as much as possible.

[ankurbhasin]

Hi Arven,

I think the best option for you will be to run HSRP on your router LAN interface and do the laod balancing. If you have everything is same subnet on your LAN you can load balance in same subnet also using multiple groups also if you have multiple subnets you can again load share with multiple group assigning few vlans/subnets for one router and anoyther for second router.

Also configure tracking for your serial interfaces so that incase your serial interface goes down HSRP can find out that your router serial is down and can make the sstandby router alsoactive for the rest of the groups.

Read this link for more details

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/cs009.htm

HTH

Ankur