Symptom
Ping to the neighbor switch doesn't work for a few minutes due to incomplete ARP information.
Conditions
Cat3k or Cat9k running any 16.x.y release. The switch has high rate of incoming traffic with no route or incomplete ARP.
Workaround
The traffic with no route or incomplete ARP is stopped.
Further Problem Description
Check the punt counters using "sh controllers cpu-interface". If lots of traffic is being constantly being punted to "sw forwarding" queue, then there is a chance that ping to a neighbor might not work for a few minutes because the ARP never resolves.
If the rate of that traffic drops or stops, then ARP gets resolved automatically and ping starts to work.
Other commands to check the punt counters and drops are:
show platform software fed active punt cpuq brief (on 9400) and show platform software fed switch active punt cpuq brief (on 3650, 3850, 9300 and 9500).
show platform hardware fed active qos queue stats internal cpu (on 9400) and show platform hardware fed switch active qos queue stats internal cpu (on 3650, 3850, 9300 and 9500).
