I am wondering how the "Last input, output" counters work on switch interfaces. I am very confused at the moment, and hope somebody can clear this up for me. According to the documentation I have read from Cisco, it simply is showing you the last time in hours:minutes:seconds since a "packet" was successfully transmitted or received on an interface. That seems to make sense, except that I am on a purely layer 2 switch (Cisco 2950), so it processes frames on it's switch interfaces not packets. Anyways, I don't understand how in many cases the "Last input" can be "never" , but the output can be something other than never.
For instance, here is a port that has a machine attached to it in a production network:
Switch#sh int status | i Fa0/14
Fa0/14 connected a-full a-100 100BaseTX
Switch#show interface fa0/14 | i Last input
Last input never, output 00:00:01, output hang never
If I ping the machine on this port, the last input stays at "never" and the last output continues to increment. I successfully pinged the machine, so I am thinking OK a frame came IN to the port I am on, was OUTPUT on the port of the machine I pinged, and when the ping reply packet was sent, a frame was INPUT on the interface the machine I pinged is on, and OUTPUT on the interface I am on. I don't get it, am I missing something here????
I have the same problem, but with different HW... I'm troubleshooting this on a 6509-E with WS-X6708-10GE.
I also decided to ping the device behind this TenGig interface and noticed the last input counter was increasing, hence I thought no traffic was passing the interface.
But then I found this:
Number of hours, minutes, and seconds since the last packet was successfully transmitted by an interface. Useful for knowing when a dead interface failed. This counter is updated only when packets are process switched, not when packets are fast switched.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...