My question is concerned with how Cisco switches use keepalive at layer 2 to detect loopbacks. All the info on keepalive that I could find was concerned with its use at higher layers (eg tunnels, routing protocols etc).
We had an incident where a mismatch in switch configurations caused a loop that wasn't blocked by spanning tree. This caused a number of our switches to err-disable their uplinks "%ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected". Some of these switches where fairly deep down a chain of switches with only a single uplink path.
We have also had a situation (which eventually went away) where the single uplink on a particular switch was err-disabled loopback detected although we could find no evidence of a loop. I have my suspicions about keepalive packets not being dealt with properly especially if vlan 1 is removed from trunk links (which we have to do in some cases) or ether channels are involved. Bugs CSCeg58877 and CSCdt82690 describe such problems but neither of these match our circumstances.
Because of the above I am considering disabling keepalive on my Cisco switches layer 2 links, especially uplinks, is this a good or bad idea?
Keepalives should not be disabled on Copper links. Only on Fiber links. If you are seeing copper ports getting error disabled , there may be a spanning tree loop in the network that you need to find out. It is recommended only to disable keepalives on the fiber ports.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.