Retrieve unknown IP if Mac is known about arping

[ThomasHabets]

Yeah it's not the prettiest of scripts. I have an old feature request to make it part of the binary, which would make it cleaner, but there appears to be little need for it (including that I've never really needed it), so I don't want to add and support a feature that nobody really needs.

[ThomasHabets]

You don't need to do any network restart. Just setting it to 0 takes effect immediately. (cat the file to confirm).

It works for me. You're saying you successfully set that value 0 zero on the target that you're pinging?

You could also try this script

[peterfarge]

I tested it again with a second debian machine and now the arping on a mac address worked :)
The first test failed, because it was a OpenWRT linux (no arping on a mac answers even though icmp_echo_ignore_broadcasts=0). If you go to the firewall menu and turn off the 'Drop invalid packets' checkbox, then I get also arping on Mac from OpenWrt. Additional there is a TP-Link router where I can telnet on, I can see that icmp_echo_ignore_broadcasts=1 but he answers arping mac requests anyway. Strange...

Your script is arping on a mac with a additional IP address parameter in a loop. It worked, regardless how icmp_echo_ignore_broadcasts is set. The problem is that there are only two routes in a normal host: One route about the localnet and a default route for all other packets. If the arping goes into another net, the packets go to the default router and he doesnt know what to do and will drop the packets. You have to add and remove a localnet-route for every subnet you are arpinging. And you have to assign a ip into this subnet for the localhost and have to test if the ip isnt already taken. And also there are some more private net ip ranges possible. I think I dont want to see such a script. Then I stick to the electricity on/off method. Thanks anyway :)