OT: VSS + MEC - port-channel dynamically cloned?

Leland Vandervort leland at taranta.discpro.org
Tue Nov 24 21:19:33 UTC 2009

Thanks Ross, 

In this case, though I cannot see where the mismatch is given that the
encapsulation, trunking (vlans allowed, etc.) and channel mode (LACP)
are all configured identically across all ports and the channel itself.

  Just wondering if it's a left-over from before the VSS migration when
the original trunks were two separate etherchannels and then migrated
them "live" to MEC... 


On Tue, 2009-11-24 at 13:57 -0500, Ross Vandegrift wrote:
> On Tue, Nov 24, 2009 at 07:51:29AM +0100, Leland Vandervort wrote:
> > Essentially, for all of the MEC connections, the VSS has created a clone
> > of the configured port-channel to bind the actual physical connections,
> > rather than binding them under the configured port-channel (and suffixed
> > the port-channel number with A or B depending on which chassis was first
> > to bind).
> IOS does this when ethernet channel members cannot join the bundle due
> to negotiation mismatch.  If the currently active elements are
> incompatible with a new element, the A/B interfaces are created.
> These are called "secondary aggregators" in IOS-speak.
> http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a0080094470.shtml#po1a

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