Discover Host on local switch with unkown net


New Member
Hello Forum,

very often I have a unknown router to fix. I dont know the current IP or Net, but I know the Mac address. I connect the router via cable to my main switch where my debian machine is also connected. Now I want to know the IP address of the router. I try 'netdiscover -i eth0', sometimes it discovers the router, sometimes not. Often I have cut off the electricity and start again. Can I make this easier? (Doesnt matter if it takes longer)

1. I tried 'arping -c 4 -i eth0 00:11:22:33:44:55'
The answer is always timeout. ThomasHabets answers this topic: /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts has to be 0 to get answers. All of my routers are set to 1, so its most likely the same with the unknown router.
2. For nmap I have to setup correct routes to the unknown router I think. If the debian machine is in the net and the unknown router is in one of the other private net and no routes are set how to reach this unknown net, the debian machine will drop the nmap packets.

I'm thinking of a program that puts eth0 into monitor mode and aggressively pings every possible host.




Staff member
Gold Supporter
very often I have a unknown router to fix.
Why? If you legitimately have access to a router you would surely know its details?

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