No proper Etherchannel load balancing

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Nov 10th, 2008
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We have etherchannel between cat6000 and cat2970. 2970 connected to many users using modems through ubr router. Etherchannel circuit is not load balancing the sent traffic towards 2970. I tried srce-dst-mac,src-dst-ip dst-ip. circuit utilization is high on single port.

I believe etherchannel load balancing is independent for each device.

i thought destination based forwarding would work but it is not.

There is no errors what so ever on interfaces

Can some one help me out.


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Giuseppe Larosa Tue, 11/11/2008 - 00:25
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Hello Chandu,

if I understand correctly your scenario is:

c6000 --- channel --- c2970 -- UBR NAS router --- users via modems

if at the other end there is only one user that is the UBR router load-balancing on MAC addresses provides no results.

Unfortunately the ubr router could be using L2TPv2 to concentrate user PPP sessions or other form of tunneling: if so even trying to load balance using IP addresses can be useless.

If you can access the UBR router is important to understand what type of traffic is sending out /receiving because it is possible that is all inside L2TP packets.

Hope to help


chandu.84 Tue, 11/11/2008 - 07:52
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Thnk you so much for your reply.

We have 802.1q tunnelin on c6000 and no type of tunnelin on cmts(ubr). I do not know how to get to know what type of traffic is passing through,..... can u kindly help me out with a suggestion.

Thnx a ton

Giuseppe Larosa Tue, 11/11/2008 - 11:19
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Hello Chandu,

I was thinking of possible reasons for a single IP flow.

The remote users accessing via modems are terminated on the UBR router ?

on the link of the UBR use

int fa0/0

ip accounting output-packets

these tell you the IP flows outgoing : inverting IP source and IP destination you should have an idea of the variety of traffic.


sh ip accounting

after some minutes

Another thought :

is the etherchannel a dot1q tunnel on the c6000 side ?

this could have an impact on what you see

Hope to help


dbellamkonda Tue, 11/11/2008 - 11:27
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Thnx yup,, etherchannel is dot1q trunk and 8021q tunnel. what impacts do we have


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