some days ago we had a layer2 loop in our network and several switches announced the following messages:
Jun 14 20:17:37.965 MESZ: %ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on GigabitEthernet0/1.
Jun 14 20:17:37.965 MESZ: %PM-4-ERR_DISABLE: loopback error detected on Gi0/1, putting Gi0/1 in err-disable state
While troubleshooting this issue we asked ourselves what is the sense of keepalive packets but we did not found any documentation in cco.
So it would be very fine if somebody could give me a detailed explanation:
- What is the meaning of this keepalive packets?
- What is the structure and content of keepalive packets?
- What is the destination address?
- How does a cisco neighbor switch handle this keepalive packets?
- How does a non-cisco neighbor switch handle this keepalive packets?
- How does a end devices (e.g. pc) handle this keepalive packets?