T1 Single router load balance recommendation

gravyboat · ‎09-01-2004

I have 2620 routers each with 2 T1 WICs load balancing between my two facilities. I had PPP multilink running and had some problems with it. I have since removed PPP multilink and just have the two links routing (using EIGRP).

My question is, will these load balance efficiently on their own or am I better off using multilink PPP or another load balancing configuration?

scottosan · ‎09-01-2004

EIGRP is very efficient with equal cost load balancing

vcjones · ‎09-02-2004

You don'tindicate why you gave up on PPP multilink (which would be my first choice). As you seem to have it currently configured, load balancing is on a per destination IP basis, so if most traffic is going to a single IP address on the other side, you are not getting the load balancing you are seeking.

If you don't want to use PPP multilink, your other option is to use CEF with per packet load balancing (look up the "ip cef" command, note that it is only available on recent IOS releases for the 26xx platform). Do NOT use "no ip route-cache" to get per packet load balancing, it will use even more CPU cycles than PPP multilink.

Incidentally, the only disadvantage to PPP multilink other than high CPU consumption is the potential for errors on one T1 to delay packets on the other T1. On the other hand, one advantage of PPP multilink is that it will maintain packet ordering even in the event of mismatched delays.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com

gravyboat · ‎09-02-2004

Hi Vincent,

Thanks for the reply. I stopped using PPP multilink because we had our T1's drop and the phone company (Verizon) insisted the lines were fine and we were having clocking errors on one of the lines.

In an effort to at least get one line up so that we didn't have one hospital down, I deleted the multilink group and as soon as I did one of the T1's came up. After removing the PPP statements from the 2nd T it also came up.

The lines seem to currently be load balancing using EIGRP, but I wasn't sure if this was as efficient as PPP multilink. I want to try and reconfigure it but bringing down a healthcare facility at any hour is a hard sell if things are currently working.

Thanks again for the info,

Rob