GNU / Linux and FreeBSD had a nifty little program (tool) called dhcping . dhcping – send a DHCP request to DHCP server to see if it’s up and running. dhcping is also able to send a request to DHCP servers on a whole network range and therefore it can e asily be used as a scanner to find any available DHCP servers in a network.
This makes dhcping a nmap like scanner capable to determine if dhcp servers are in a network 😉
To scan an an entire network range with dhclient and find any existing DHCP servers:
noah:~# dhcping -s 255.255.255.255 -r -v
Got answer from: 192.168.2.1
received from 192.168.2.1, expected from 255.255.255.255
no answer
In above’s output actually my Dlink wireless router returns answer to the broadcast DHCP LEASE UDP network requests of dhcping .
On a networks where there is no DHCP server available, the requests dhcping -s 255.255.255.255 -r -v returns:
noah:~# dhcping -s 255.255.255.255 -r -v
no answer
This article was inspired by a post, I’ve red by a friend (Amridikon), so thx goes to him.
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Tags: Amridikon, answer, Auto, broadcast, dhclient, DHCP, dhcp request, dlink wireless router, Draft, entire network, freebsd, GNU, gnu linux, Got, LEASE, Linux, nbsp, network requests, nmap, noah, post, range, request, scanner, servers, thx, tool, UDP
