usually this means unknown unicast flooding takes place. There can be few reasons. First the host receiving the traffic could be not sending any frame with its source MAC within the MAC address table timeout (5 min per default). Solution: trigger a ping every minute from this host (small script).
Second this could have to do with HSRP and spanning tree. The underlying reasons and possible problem solutions are very well described in "Unicast Flooding in Switched Campus Networks" found at
thanks for the feedback. I had seen this article before. In a simple form, we can see two hosts, both going through one switch, ftp or nfs. The target mac address ages out of the mac table, which causes the flooding. If we setup a ping to the target and ping it <5 minutes (before age out) then there is no flooding at all. I do not understand how during a very long ftp session or nfs, the targets mac ages out? thanks in advance.
What subnets are the two servers on? Which vlans? Where's the routing for the vlan being done? Whats STP decided the best path between the switch and the router(s) for each VLAN? (it -could- be different in PVST.)
It shouldn't happen if they're on the same switch and on the same VLAN.
this ended up being udp traffic. The nfs server never responds to the client, with a any tcp connection, confirmation or keep alive. So, the mac-addy of the server would time out and the switch wouldn't know where it was, and then flood traffic. If I set up a periodic ping (<5 mins) to the server, I kept the mac-add fresh in the table, and the flooding stopped. Discussing having the nfs client/server have a keep alive sent between them, or enable pruning as well to limit the flooding.
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.