multilink load sharing ?

Unanswered Question
May 21st, 2007

If I have a multilink of 4 serial T1 interfaces how does traffic share across the circuits ?

Can this be changed with CEF ?

I am wondering if traffic would fill the T1's in sequential order or does it put packets across all four at once ?

I may have one bad T1, trying to see what I can do or if I should just take it out of the multilink bundle.


I have this problem too.
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Richard Burts Mon, 05/21/2007 - 13:06


Configuration of CEF (or removing CEF) or changing its loadsharing method will not affect the way that multilink distributes traffic. Multilink manages its own usage of the links and should spread the packet data across all available links in the bundle all four at once.

If you think that you have a bad T1 you might remove it from the multilink bundle and see if performance changes. This would also make the T1 available for testing purposes.



dangal.43 Mon, 05/21/2007 - 13:11

rick, somewhere i read that in multilink Data Packet is fragmented as per the number of link participating in the Mulitlink group. for exam ple if you are bundle the 4 T1 link then it will fragment the single packet in to 4 small fragment of same size and then send the each fragment on each link.

is that correct?

Richard Burts Mon, 05/21/2007 - 13:18


In general (especially with equal capacity pipes) I believe that is what it does.



dangal.43 Mon, 05/21/2007 - 14:55

what are the others loadbalancing feature we can configure on the multilink?

minumathur Mon, 05/21/2007 - 19:05


Multilink sharing there own to distribute data, so no relation with CEF, if you have 4 E1 in multilink configuration and any of the link will having high error, there one command to put thresold limit.


Richard Burts Tue, 05/22/2007 - 05:34


I do not believe that there are any other load sharing features that you can configure on multilink. The multilink is treated as a single entity for routing purposes and has a single IP address which is used for any traffic going over any of the links within the bundle. The routing process gives IP packets to the multilink to forward and you have no control after that.




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