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Referring page - [[NAD710 Lab 2]]
'''1. What is the effect of the first "ifconfig ethxx down" command on the system's ARP cache ?'''
''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 ?
A file called gc_stale_time defines the timeout for arp cache. You can find this file in /proc/sys/net/ipv4/neigh/eth1
[[Category:LUX]] [[Category:NAD]]
