[SW1]G1/1----------------G1/0/1[SW2]
I have two switches trunked with a cat5e cable. I am seeing loopguard blocking on SW2 every few minutes which is interrupting user connections because the port goes into inconsistent state for a few seconds. It seems to affect all VLANs. SW1 is root and never shows anything out of the ordinary and downstream ports appear as designated. I need to schedule maintenance window to replace the cable, but Cisco doc says "Copper ports are normally not susceptible to this type of issue, as they use Ethernet link pulses to monitor the link." What are other possible causes?
%SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port GigabitEthernet1/0/1 on VLAN0995.
%SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port GigabitEthernet1/0/1 on VLAN0992.
%SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port GigabitEthernet1/0/1 on VLAN0992.
%SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port GigabitEthernet1/0/1 on VLAN0999.
%SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port GigabitEthernet1/0/1 on VLAN0995.
%SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port GigabitEthernet1/0/1 on VLAN0999.
%SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port GigabitEthernet1/0/1 on VLAN0415.
%SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port GigabitEthernet1/0/1 on VLAN0412.
%SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port GigabitEthernet1/0/1 on VLAN0409.
%SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port GigabitEthernet1/0/1 on VLAN0420.
