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New Member

Etherchannel and STP

Here is my hardware setup

Dual C6K 6509 w/SUP2/MSFC2/PFC2


Switch Fabric Module 2

16 port GIG-E modules (Shortwave)

I have configured an 8 port etherchannel bundle between the two switches, same admin group.

I would like to figure out how I can determine which link in the bundle is passing STP PDU's. I know the switches load distribute traffic (U/B/M), does this include STP as well?

Thanks in advance for any help

New Member

Re: Etherchannel and STP

STP BPDUs are not load balanced across the EtherChannel bundle. They go out the first link of the the channel.

New Member

Re: Etherchannel and STP

Thanks for the info!

I assume you are referring to the first port listed when initially configuring the etherchannel bundle.

Is there a way within the switch to verify this, or do I need to use outside tools?

New Member

Re: Etherchannel and STP

Yes, the first member of the active channel.

I don't believe there is an easy way through the CLI you can verify which port within the channel is actually transmitting BPDUs. You could try using the

"show spant stat m/p " command and look for "channel_src_mac". The MAC address here is the actual MAC address of the Port on the switch. "sh mod" displays the range of Port MAC addresses applicable to the modules. Look for "channel_src_mac" address on the switch connected to the root bridge. Because BPDUs are being originated from root. This will tell you which member of the channel from the root is actually sending BPDUs.

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