How do I find all my DHCP servers 1

[DanZeMan]

Is there a (simple?) way to search through my network to find all servers running the DHCP service?
I have someone asking the same question for RAS as well.

Any help appreciated.

 

[lhuegele]

How many servers do you have in your environment?

 

[DanZeMan]

1200, spread across the globe.
We are undergoing a DHCP consolidation, and want to see what servers are still running the service, and ensure that we have consolidated to the correct degree...

 

[Aslamvs]

Well, you can try this

1- Disable the known dhcp server, and have a node release/renew it's dhcp-assigned address. If it gets one then you know there's another DHCP server.

2- Do the same thing as above but not necessarily shutting the other one
off. Just look at the packets and after a DHCP request goes out, see who responds.

3- Ask around and try to find out who was the dumbass that is responsibe ;-)


A fourth suggestion would be to install a Sniffer/Analyzer program, to see what's going over the line. You'd be specifically looking for
DHCP-acks or Nacks.

sniff traffic on udp ports 67 and 68.

Alternately, run a port scanner on udp port 67 over your nets, and anything that is 'open' is a potential DHCP server.

Hope this Helps


Aslam

 

[Aslamvs]

One more from microsoft if you are using windows200

http://www.microsoft.com/resources/.../server/reskit/en-us/deploy/dgcf_inc_bbut.asp

Have a look.

Unauthorized DHCP Server Detection
The DHCP service for Windows 2000 is designed to prevent unauthorized DHCP servers from creating address assignment conflicts. This solves problems that might otherwise occur if users created unauthorized DHCP servers that could assign invalid IP addresses to clients elsewhere on the network. For example, a user could create what was intended to be a local DHCP server by using addresses that are not unique, which could lease the addresses to unintended clients requesting addresses from elsewhere on the network.

The DHCP server for Windows 2000 has management features to prevent unauthorized deployments and to detect existing unauthorized DHCP servers. In the past, anyone could create a DHCP server on a network, but now an authorization step is required. Authorized personnel usually include the administrator of the domain that the Windows 2000 Server platform belongs to or someone to whom they have delegated the task of managing the DHCP servers.



Aslam