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QOS on port channel

What is the recommended way to do QOS on a etherchannel bundle ? I have 4 gig ports (Copper) between two 4506 which are port channeled. Should QOS be applied on all four physical ports or on the port-channel interface ?

New Member

Re: QOS on port channel

If you are going to do QOS for voice, I think (?) you will have to remove the port channel config and config QOS on the individual interfaces because of 2 reasons:

1) I found the excerpt from the "Understanding PortChannel" section of the 4500 Switch Config docs:

Note QoS does not propagate to members. The defaults, QoS cos = 0 and QoS dscp = 0, apply on the port-channel. Input or output policies applied on individual interfaces are ignored.

(VERY CONFUSING, as it makes it seem like you CAN'T even config QOS for port-channel??)

2) If all the member interfaces' QOS config parameters don't match EXACTLY you will get errors such as this:

I couldn't find anything in SRND or best practices, so, like I said, I would stick with getting rid of the port-channel config and adding it to the individual interfaces.

Re: QOS on port channel


Appreaciate your reply.

Getting rid of the port-channel is not an option as these two switches are core switches, and do need that kind of b/w (4 gigs) between the two switches.

I forgot to mention that i am looking at QOS for voice. Looks like I may have to live with no qos config, unless I get rid of the port channel config.

New Member

Re: QOS on port channel

hanky, I really respect your depth of knowledge. I am amazed with the stuff you put on here! Way to go...

For the QOS for port channel (and other similar virtual load balancing interfaces) you can apply the qos config right to the physical member interfaces. I did this on a 3750, and it seemed to work. the junk data was limited by mqc's "shape average" down to 1mb. I was matching with an ACL. I would open a tac case, and perhaps put the results here...

One caveat, on the 2811's I have worked with, we applied the "service-policy" on the multli-link 1 interface when we used MLPPP with 2 or more T-1's.

Re: QOS on port channel


I tried this on a 6500 last week on physical ports and that seem to work. I will go ahead and check it out on the 4500...

Thanks for your feedback.

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