i have an small issue with etherchannel, when i create a port-channel in a VSS c6506, the main Po goes down and create another one in parallel with the letter A
Port-channel132 unassigned YES unset down down
Port-channel132A unassigned YES unset up up
132 Po132(SD) LACP
132 Po132A(SU) LACP Gi1/9/12(P) Gi2/9/12(P)
so my question is, why this duplicate Po ? i know if there is a mismatch between 2 ports, it will create a second port-channel, but here, the two ports are in the same Po but not in the main Po... if i shut this Po, it will renegociate the Po, sometimes the main Po becomes up, and sometimes no.
i read the Cisco document about the port-channel, but there is no explanation for this comportment. anyone can explain this?
thanks a lot
Do you have this command?
mls qos channel-consistency
According to the document here http://docwiki.cisco.com/wiki/Issue_Description:_Creation_of_a_Secondary_portchannel_%22PortChannel_1_and_1A%22_with_LACP_channel_protocol
a secondary portchannel will be created if :
1. Adding a new port to an existing port channel. If any configuration mismatch is seen on the newly added port, it will be added to Secondary port-channel as you can see (Here, Po1A)
2. Configuration mismatch on the ports bundled in the port channel.
3. Configuration mismatch on the interfaces of the far end device can also create inconsistency between the ports bundled in the port channel.
This is expected behavior. The exact reason will be shown in the Logs while adding the port to port-channel.
These ports are called Aggregator ports Po32A(SU) and are put in a Suspended state
It's because Port-channel noticed difference in configuration and was not able to bundle ports together. Secondary aggregator Po32A will keep the port up but will work as a separate port, like you did not have port-channel at all. What are these ports connected to?
Please see below link for some more info on aggregartor ports
Can this condition as be caused by port-configuration not being matched. Would having MLS QOS on the 6500 and no MLS QOS on the Nexus 5K links ?
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,60,901,902,904,955
switchport mode trunk
mls qos trust cos <--- will removing this resolve the channel group ?
switchport mode trunk
switchport trunk allowed vlan 1,60,901-902,904,955
I can assume two scenarios:
1. If port settings mismatch: Both the ports will fall in different port-channel group. If Gig1/1 & Gig1/2 have a mismatch, then they will form two port channel say Po132 & Po132A (alternate aggregator). Gig1/1 will be part of 132 and Gig1/2 will be part of 132A.
2. If port settings matches but doesn't match with port-channel settings: Then both the ports will form a alternate aggregator and main port-channel will remain empty or down - this is happening in your case.
You need to check the port-channel settings or capabilities and compare them with the physical port settings/capabilities.
Just for hint, check flow control or storm-control settings.
thanks for replies, i have to test it but it seems it was a mismatch in flowcontrol. but i have to test it to be sure.
if it's that, i'll come back to give you my feedback and mark as good answer.
thanks for help,