I would like to know what is the most effective way to detect the source of a L2 local loop on a LAN causing high CPU for several switches and big slowdowns on the network. I was thinking about two differents ways but not sure they work:
- Perform a sh-mac-address on the switches to look at the duplicate mac-address ?
- Capture the traffic ? (Quite difficult on a big LAN when you have no idea of where the loop could be !)
Don't hesitate to let me know what you think about it. I just would like to know how to react before it happens on my LAN (... and unfortunately i'am sure it'll happen one day ;) )
Hope it never does happen to you. Happened to me a few times and unless you are quick you won't be able to log on to the switches never mind look at the mac-address tables.
Attached is good doc from Cisco about troubleshooting STP. One of the key things is to have a diagram of your L2 topology in terms of redundant links, which switches are STP root and secondary. If you don't explicitly set which switches are root and secondary for vlans i strongly recommend you do as it's the last thing you want to be trying to find out in a broadcast storm :-)
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.