Load balancing on lease line.

[kvashisht]

Hi,

I have two lease lines from two diffent ISP's & connected two a single router 1720 on wic-2t card. Now i want to forward my packet on both the links for gaining load balacing feature. how it can be possible.can i use "backup interface command" on serial port assigning the second serial port as backup.


Regds,
Kaushal Vashisht

 

[Piass]

A routing protocol such as OSPF should do equal cost load balancing. Then depending on the switching type, the router should load balance per destination or per packet.

 

[baddos]

Load balancing on two different ISP's using per packet mode isn't a good idea. This can lead to packets arriving out of order to their destination. The best way to load balancing across isps is on a per destination, but this will require taking a lot of routes from the isps.

I would recommend setting up BGP to take the ISP's customer routes and a default route. This way your router will have the closest route to the different isps and a default route for any other route it doesn't know.

 

[IllegalOperation]

To add to this question, I purchased two T1s from the same provider....as it was less costly than a single frac DS3.

If I have a 7204VXR, would I be able to effectively use load balancing with these two circuits? As in sending 50% of the traffic out one circuit, with the other 50% sent out the other circuit?

Thanks

 

[baddos]

Yeah... Try something like this

configure terminal
ip cef
interface ethernet 0
ip load-sharing per-packet


Make sure that you have two equal cost default routes too.

ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.1
ip route 0.0.0.0 0.0.0.0 xxx.xxx.xxx.2

Then it will loadbalance per-packet. Probably won't be an equal load since some packets are bigger than others, but it will be pretty close.

 

[tbilan]

There is no way to effectively load balance these circuits since the destinations and routes are not equivalent. You load-balance when you have 2 circuits running parallel path to a 2nd router to effectively give you a 3MB circuit. If you want a 3MB circuit you need to order two T1 from the same provider and have it connect to their same router.

In your situation what you want to do is throw out that 1720 and purchase a 3700 or 7200 with 128+ MB RAM and get BGP running two both of those ISPs so your router can do it's job by sending packets to the ISP with the shortest route to the destination. This is the best situation but also the most complicated.

A no-intelligence load-balancing config would be to do cheese routing and put some routes in your router to have it pick interfaces based on your input:
ip route 1.0.0.0 224.0.0.0 serial0
ip route 32.0.0.0 224.0.0.0 serial1
ip route 64.0.0.0 224.0.0.0 serial0
ip route 96.0.0.0 224.0.0.0 serial1
etc.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE