Recently we started seeing higher ping replies from a switch, which I realize in itself is not an indication of a problem, but this is the only switch that has a high count of "Tx Mode Drop" and "Sa Miss". I am unsure how to debug further and try to figure out where these packets are coming from and why they are being kicked up to the software and being dropped. I am hoping someone can make a suggestion for debug/troubleshooting techniques in order to figure out the cause of the CPU utilization.
I could not find any reference to what the reason "Tx Mode Drop" means, debugging is an issue because this only occurs during production hours, which consists mostly of multicast traffic. This switch is used as a core routing switch.
Re: C4900M High CPU utilization and dropped packets
SA Miss = This CPU event, is caused when a new MAC is seen on the port, and it is thus, a copy of such packet is forwarded to CPU for MAC learning.
TxModeDrop = This copy of packet is then dropped by CPU once it has been processed, and the counter increments. So, when a packet encounters SA miss event, a copy comes to cpu and it is dropped as a TxModeDrop.
Generally the cause of too much SA miss, is MAC flapping, caused either due to network loop or server with improper NIC binding, resulting in MAC's seen on different port of the switch, and causing SA Miss event.
Can, you check logs and see if any MAC flapping logs are observed during that period. I am not 100% sure, but it is by default enabled on 4500, if not then configure this command to find details of such frames:
"mac-address-table notification mac-move"
You may try to Span packets hitting CPU, using this procedure:
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.