DHCP server. How to find servers on the network?

Question

DHCP

What threatens the presence of two dhcp servers in the network? How can you avoid address conflicts on the network? by what means it is possible to find additional (superfluous) dhcp servers?

Answer 1

umm. Maybe it's time to educate yourself? otherwise the question obviously pulls on the sheets so ... give explanations

Answer 2

run tcpdump and wait for BOOTP/DHCP Offer from dhcp servers,
several dhcp servers, depending on the settings, it is fraught with the fact that the client may receive an address from the wrong dhcp server from which you expect, with all the consequences

Answer 3

having two servers. with each request for an ip-address from a client, it will receive it from the server from which the packet arrived earlier.
avoid ip address conflicts. when assigning manually - keep a list of assigned addresses, do not give users the rights to change ip-addresses. if assigned automatically, configure a DHCP server (one), do not give users the rights to change ip addresses, prevent other DHCP servers from appearing on the network (protect network switches from unauthorized access, use DHCP snooping on switches, if supported).
find extra DHCP servers. run Wireshark on the computer. force the computer to re-obtain an ip-address (for example, by pulling out a patch cord). analyze the result. if the responses to the request came from different MAC addresses - see what MAC address the correct DHCP server has; the rest are therefore redundant. then you can search for them, if you have managed switches, you can see on them which physical port of the switch is assigned the MAC address of the extra DHCP server.