2 x 2Mb MPLS Connections to 1 Data Centre

Unanswered Question
Feb 27th, 2009

If we had 2 x 2Mb MPLS connections from a single site\subnetwork to a Data Centre could we make use of both of those connections simultaneously? I'm trying to get my head around how it could work, if at all possible?

I have this problem too.
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Edison Ortiz Fri, 02/27/2009 - 08:07

If the same routes are learned via both links, CEF will load-balance the traffic.




garybeach Fri, 02/27/2009 - 08:16

Hi Edison

Thanks for your quick response.

If I'm understanding you correctly, would we use one router with one Internal Interface for the LAN but with two External Interfaces, one connected to each MPLS line? And would this traffic be load balanaced?

Would the Data Centre Router route traffic to our site in a load balanced fashion down our 2 MPLS links?

How would this work in a BGP network config?



Edison Ortiz Fri, 02/27/2009 - 08:21


And would this traffic be load balanaced?

If you issue 'show ip route' and you have 2 routes installed in the routing table with different next-hop address, then that traffic will be load-balanced.

CEF uses the src-dst load-balanced. In other words, if a source is sending traffic to a destination - it will use one of the 2 links for the entire transmission. If the same source establishes another session with a different destination, the 2nd link may be used. CEF uses a very complicated algorithm thus is very hard to predict which link it will use for the src-dst pair but it will try to load-balance the traffic.




Joseph W. Doherty Fri, 02/27/2009 - 09:49

Also, CEF offers a per-packet load-balancing, which will better utilize your two links although at the risk of changing a flow's packet sequencing.


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