2nd DHCP server

I have 2 DHCP servers on my network but I don't know where the other one is.
My Android phone seems to always get an IP from the rogue server (I need to find an app that displays the IP, DHCP Server, DNS servers, subnet, gateway).
The default Android settings on my phone don't show it. :frowning:

I rebooted my openwrt router and most things seemed to get IPs from the rogue server and they had non-functional gateways (I don't know why my phone kept working :-().

How do I list all DHCP servers on my network?
I found a Windows exe to do it but I need a Linux way. :slight_smile:

Just run Wireshark or tcpdump and capture the DHCPOFFER messages:
https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#Offer

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find mac address
lookup mac address should give you brand of device
may point it out to you

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angry ip scanner looking for an open port 67 (then get the mac info as well) might also work
The server listens on UDP port number 67, and the client listens on UDP port number 68.

Are you running a pihole machine in your network by any chance?

P.S. An Angry Ip Scanner scan on your entire subnet can find alot of open things...really helps find out what should and SHOULDN'T be on your network (static or dhcp)

DHCP uses UDP, not TCP. Scanning generally doesn't see UDP ports.

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