If the host is down, ARP requests will time out and router will send ICMP error "Host unreachable". ARPs are not sent for every packet received for the unknown destination. I think they are repeated every five seconds and after few attempts the router timesout.
Too many ARPs, though not healthy for a network or the router, usually don't crash it.
If you statically add an ARP for some IP address in the ARP table, router wont ARP request for that entry, as that entry will be treated as permanent in ARP cache table.
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...