* After disabling the cache, you can issue the command ip neighbour show <ip of Comp B>

when the cache is still there its is gonna show 172.16.1.2 dev eth1 lladdr 00:16:76:32:07:12 PERMENANT (never expires;never verified), then it changes state to STALE (STALE means still usable :needs verification), then the arp cache is lost. It took approx, less then 3 mins for arp cache timeout. Then when you give the command arp -na, the cache is empty