MPL Bidirection load sharing

Unanswered Question
Feb 2nd, 2009

Hi All,

I have two 2821 routers in my lab each with a VWIC-2MFT-T1-D1 having the two T1's multilinked. The routers are working and both back-to-back connected with a cross over cable. All data transfers are great during low usage.

My problem happens when I send large files across the multilink at the same time. What I see is one direction gets all the bandwidth while the data transfers in the other direction remains idle or very low resource allocated to it. Once the first transfer (the one that gets all the bandwidth) completes, the next transfers gets all the available bandwidth. I this behavior might be analogous to half duplex vs. full duplex.

I would think/hope that the bandwidth is shared for both up-stream and down-stream traffic at the same time without the need for any QOS set up.

Anyone have any ideas on a conf issue or other thoughts?

Thanks for any help,


I have this problem too.
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Giuseppe Larosa Mon, 02/02/2009 - 23:55

Hello Tom,

to help understand the issue post the output of the following command:

sh ppp multilink

and the configuration of the multilink interfaces on both routers

PPP multilink should be able to use the links fairly by using its own fragmentation process so that big packets are divided in two PPP fragments one using first the second using second link.

Hope to help



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