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?
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
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.
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