Hi everyone, I'm having difficulty with etherchanneling. The situation is like this.
I'm using a Aruba WLAN controller to form a etherchannel with a Cisco switch. Two interfaces Gi5/1 and G5/2 are binded into Port channel 3. The channel mode is on so that neither PAGP nor LACP is used. This is the only link between the two devices and it only carries VLAN812. VLAN 812 is also trunked across the two Distribution switches, and no other devices contains this VLAN. The Aruba controller is STP enabled with the parameter of standard 15-2-20-32768.
The problem comes when I shut or unplug one linke, the other link will turned into Loop inconsistency mode and the whole channel goes down
Sep 5 12:45:48: %SPANTREE-SP-2-LOOPGUARD_BLOCK: Loop guard blocking port Port-channel3 on VLAN0812.
Sep 5 17:12:17: %SPANTREE-SP-2-LOOPGUARD_BLOCK: Loop guard blocking port Port-channel3 on VLAN0812.
This is a bit confusing as loop guard will only work on non-designated ports but the port Po3 is a root port:
ADMIN2>sh span vlan 812 | in Po3
Po3 Root FWD 3 128.835 P2p Peer(STP)
Can anybody give me some hint on why this is happening? Thanks!