My network currently has two distribution switches (Catalyst 6513). Please refer to attached diagram for further details.
Yes, it looks weird but I'm actually required to loop two cables from Core2 back to itself. I need to configure both ends in their own etherchannel and different VLANs (359 & 360). The laptops are expected to be able to ping to each other.
After shutting ports 12/6-9 and then configured the necessary, I enabled ports 12/6 and 12/8 just to do a simple test. However, I received the following error messages:
%SPANTREE-2-CHNMISCFG: STP loop - channel 12/8-9 is disabled in vlan/instance 360
%SPANTREE-2-CHNMISCFG2: BPDU source mac addresses: 00-12-7f-27-1a-75, 00-12-7f-27-1a-77
%SPANTREE-2-CHNMISCFG: STP loop - channel 12/6-7 is disabled in vlan/instance 359
%SPANTREE-2-CHNMISCFG2: BPDU source mac addresses: 00-12-7f-27-1a-77, 00-12-7f-27-1a-75
%ETHC-5-PORTFROMSTP:Port 12/8 left bridge port 12/8-9
%ETHC-5-PORTFROMSTP:Port 12/6 left bridge port 12/6-7
I also captured detailed logs on Core2 in the attached file.
Referring to the following technote to troubleshoot, I can't find any reason why this happened. I was only enabling a pair of the links.
Understanding EtherChannel Inconsistency Detection:
Can someone kindly shed some light on this issue? Secondly, is it a good practice to loop cables to "bridge" two VLANs in typical switching environment? Based on my experience, STP sometimes may converge unpredictably in some switches.