[c-nsp] CEF Load balancing over Etherchannel (3750)

[Stig Johansen]

>Does anyone know how to make CEF load balancing work over etherchannels

>and actually load balance on the etherchannel?
>I have two GEC interfaces with 2 ports in each, and then I have two 
>routes multipath, one to each GEC interface
>The problem is that the CEF algorithm is the same as the etherchannel 
>algorithm and each one of the etherchannels ends up only sending out
one 
>of the two ports so it is not load balancing.   I have tried changing 
>the port-channel load-balance setting to various things (I can not use 
>MAC because it's from one router to another) and I have tried changing 
>the cef load sharing algorithm.
>Maybe this is a limitation of the 3750 platform? I have not tried this 
>on any of the other equipment.

Hi there,

I guess you have tried it, but here goes anyway..
Do you have several different source AND destinations IP-adresses using
these links? If so, setting the following should be of some help:

! Set etherchannel load-balancing to use a <source IP> XOR <dest IP>
hash
port-channel load-balance src-dst-ip
! Set CEF algorithm load-balancing to use a different seed for the
hashing
ip cef load-sharing algorithm universal 1

If you have only one source-IP, this could mess up the hashing somewhat
and reault in only one (or possibly a very skewed distribution) link in
each of the portchannels to be used.

If this is/has been tried and proven wrong, it was at least worth a try
:)

best regards,
Stig Meireles Johansen