10G wan etherchannel bundling between 12410 routers or between CRS-1 router

Unanswered Question
Jan 5th, 2009

How etherchannel/bundle ether will behave on the N*10G wan links between the 12410 routers and when running between the 12410 and CRS-1 routers and also when running between 2 CRS-1 routers ??

How it is advantageous compared to the normal CEF based load balancing on these above routers without etherchannel or bundle ether configured on them.

Any suggestions on this ??

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Giuseppe Larosa Tue, 01/06/2009 - 02:37

Hello Rajesh,

I would recommend to use CEF on parallel IP links.

Etherchannel on routers can create problems: first of all load balancing can be unfair

some network management options can be a problem (for example some years ago on a GEC on 12000 was not possible to monitor traffic with netflow).

I would stay away from bundle of 10GE ports on GSRs or CRSs you can have up to 16 IP parallel links.

Hope to help


rsivasubramanian Tue, 01/06/2009 - 08:58

hi giuseppe

thanks for the reply.But etherchannel in crs-1 routers has different load balancing methods like ports,ip and some others.

whereas cef will do src n dest load balancing?

can it make any difference

Giuseppe Larosa Tue, 01/06/2009 - 10:11

Hello Rajesh,

we are speaking of high end routers that are expected to process tens of thousands of flows per second even just differentiating on source and destination ip addresses there should be enough variety in your traffic to use the parallel CEF links in a fair way.

CEF uses an EXOR of ip source and ip destination and an hash seed that changes only when the system is reloaded.

etherchannel can use EXOR of different fields:


IP SA exor IP DA

L4 SA port exor L4 DA port

but only one of them applies to a type of traffic at a specific time.

Or you expect a few very high volume flows on the links (DR or DB synchronization just to say)

So to answer your question, unless used for connecting two data centers, I don't expect to gain in fairness by using a bundle.

Hope to help



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