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''The function of the script is to keep reading the output of the arp cache (arp -n command) each second until the mac address of the computer B disappear''
A variation on the above involves three simple steps:
1 Increase the scrollback in the terminal to 2000 lines
2 Issue the ping command to refresh the ARP cache
3 Issue the following command into the shell:
while x=0; do echo -n ''; ip neighbor show; date; sleep 1; done
The shell will display the ARP cache status and the time, every second. When the ARP cache entry times out, hit <CTRL><C> to stop the display and then figure out the difference between the start and end times.
* 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
* How to change ARP cache timeout ?