No proper Etherchannel load balancing

Unanswered Question
Nov 10th, 2008

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.


I have this problem too.
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Giuseppe Larosa Tue, 11/11/2008 - 00:25

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

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

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

Thnx yup,, etherchannel is dot1q trunk and 8021q tunnel. what impacts do we have


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