How to check how many DHCP servers in lan segment?

[zaccaz]

hi there, is there any tools (freeware preferred, win32 preferred but linux also ok) to check how many DHCP servers in a particular lan segment, & their corresponding ipaddr?

many thx!

 

[Grenage]

I'd personally just sniff the network, you can then filter by DHCP requests and responses. Look at ethereal etc for windows or tcpdump in *nix.

"We can categorically state that we have not released man-eating badgers into the area" - Major Mike Shearer

 

[Geates]

You can query AD. This code sniffs ALL DHCP servers in AD and parses the output. From there, you can visually identify those DHCP server on a particular network segment.

'DHCPsniff.vbs
'Daniel M. Jones
'August 27, 2009

strDomainName = "dc=my,dc=domain,dc=com" ' my.domain.com
strFileName = "c:\result.txt"

set objCont = GetObject("LDAP://CN=DhcpRoot,CN=NetServices,CN=Services,CN=Configuration," & strDomainName)
set objFSO = WScript.CreateObject("Scripting.FileSystemObject")
set objFile = objFSO.OpenTextFile(strFileName, 2, true)
set objShell = WScript.CreateObject("WScript.Shell")

colDHCPServers = objCont.GetEx("dhcpServers")

for each strDHCPServer in colDHCPServers
strIP = mid(strDHCPServer, 2, inStr(strDHCPServer, "$") - 2)
strServerName = right(strDHCPServer, len(strDHCPServer) - inStr(strDHCPServer, "="))
strServerName = left(strServerName, inStr(strServerName, ".") - 1)
objFile.Write strServerName & ": " & strIP & vbNewLine
next

objFile.Close
objShell.Run(strFileName)