11-23-2009 03:34 AM - edited 03-06-2019 08:41 AM
Hi All,
Just doing some digging here, but can't find any reference to it in any of the docs.
We have a few paris of VSS running, and having brought the down-stream access-switches online using MEC we note that the active port-channel that they bind under isn't actually the one configured, but rather a CLONE of the configured one which appears to be dynamically generated.
In our case, all ports and port-channel configurations are set to dot1q encapsulation and trunk mode active.
For example, we have a 3560 MEC'd to the VSS:
the MEC comes up, but under a slightly different port-channel identifier:
Here's the 3560 side:
interface status:
Gi0/49 connected trunk a-full a-1000 1000BaseSX SFP
Gi0/50 connected trunk a-full a-1000 1000BaseSX SFP
Gi0/51 connected trunk a-full a-1000 1000BaseSX SFP
Gi0/52 connected trunk a-full a-1000 1000BaseSX SFP
#sh int po1 | i Member
Members in this channel: Gi0/49 Gi0/50 Gi0/51 Gi0/52
Here's the VSS side:
Interface status:
Po11 CISCO C3560 A01 notconnect 1 auto auto
Po11A connected trunk a-full a-1000
#sh int po11A | i Member
Members in this channel: Gi1/1/33 Gi1/1/34 Gi2/1/41 Gi2/1/42
#sh cdp nei | i hacc01-d
hacc01-d Gig 2/1/42 140 S I WS-C3560G Gig 0/50
hacc01-d Gig 2/1/41 140 S I WS-C3560G Gig 0/49
hacc01-d Gig 1/1/34 161 S I WS-C3560G Gig 0/52
hacc01-d Gig 1/1/33 161 S | WS-C3560G Gig 0/51
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).
Config for port-channel and interfaces all match:
VSS SIDE:
interface Port-channel11
description CISCO C3560 A01
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 40-48,51,400
switchport mode trunk
mtu 9216
end
ACCESS Side:
interface Port-channel1
description DIST-VSS-EQX1
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 40-48,51,400
switchport mode trunk
mtu 9216
end
I'm not overly worried about it since the MEC is working with the dynamically generated port-channel, and traffic is flowing correctly... just curious as to why it uses a clone of the configured port-channel, rather than the actual configured port-channel itself. Just find that a bit strange.
Thanks,
Leland
12-04-2009 05:14 PM
Hi,
The Po1A/Po1B are LACP secondary aggregators (also know as lacp sub-channeling). This is a LACP behavior. So you won't see this with PAgP.
There could be several reasons leading to the creation of secondary aggregators, one of them being a small misconfiguration between some of the physical members of the port-channel.
In your case, if all the ports configured to be in Po1 are in Po1A (from show etherchannel summary), you can do a shut/no shut on the Po interface.
It will rebundle all the port in Po1.
Hope this helps,
Regards,
Samuel
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