CEF vs. Multilink

IT Man

Greetings,

I have two routers connected using two T1 lines per router for load balancing. Right now we are using cef with the default per destination setting. At times, we see that one line will be using around 90% while the other is barely at 25% and vice versa. I was wondering, from your expert opinions, would you recommend using cef per packet or set up a multilink on each router and let that handle the load balancing.

Thanks

PS -- It is only data being transferred, not voice.

gojericho0

In a lot of our setups we use multi link for the T1s and it works really well. My customer has not complained at all as well.

IT Man

gojericho0 wrote:

In a lot of our setups we use multi link for the T1s and it works really well. My customer has not complained at all as well.

Have you ever set up a VPN connection between 2 sites using the multilink interfaces?

joshgibson82

we had a similar issue once before where we had two T1 MPLS circuits coming in and CEF was causing one link to be over-utilized. I can't remember what exactly had to be done to fix it though. We connected to two different PE routers and there might've been some BGP tweeks done to correct the issue. I'll check around and try to find out exactly what happened.

marlon23

I would go for CEF per-packet load balancing. I would prefer it becouse with multilink you would have additional PPP header overheat which is not that much, however you can run into MTU issues and your voice traffic wouldn't like it as well. Another advantage would be that if want to avoid out of order voice packets, you can use policy routing to put voice traffic to use only one of 2 T1 links (Dont know how to do it with multilink).

The magic whisper for your interface sounds : "ip load-sharing per-packet"