looking for a utility to test DHCP settings

Question

Iv'e recently installed DHCP server (isc-dhcp-server) in my workplace.

I'm looking for a utility to test the network DHCP settings from a remote machine (not by using dhclient / iptables /renew).

• indication of the responding server (sometimes my colleagues install by mistake DHCP services)
• the ability to provide a MAC address (to test pool reservations)
• simple display of the response

for example:

$> [utility name] [source mac address | optional] ...

RESPONSE (DHCP Server is 192.168....)
    IP: 192.168.....
    SUBNET: 255.255.....
    DEFAULT GATEWAY: 192.168.....
    ...

Answer 1

You can try out the "dhcping" utility. On CentOS/RHEL, you'll have the option to "yum install it" after you'll gain connectivity to the EPEL repository. Check out the command options. They seem really relevant for your needs.

dhcping(8)                  General Commands Manual                 dhcping(8)

NAME
   dhcping - send a DHCP request to DHCP server to see if it’s up and running

SYNOPSIS
   dhcping [-v] [-q] [-i] [-r] -t maxwait -c client-IP-address -s server-IP-address -h client-hardware-address [-g gateway-
   IP-address]

DESCRIPTION
   This command allows the system administrator to check if a remote DHCP server is still functioning.

   Options are:

   -v   Verbose, print some information.

   -i   Use DHCPINFORM packets.

   -r   Use DHCPREQUEST packets (default behaviour).

   -q   Quiet, print nothing on the screen.

   -t maxwait
        Maximum time to wait for an answer from the server in seconds.  Default is 3 seconds.

   -c client-IP-address
        Request this IP address. Note that this is also the IP address the answer will be sent to.

   -s server-IP-address
        Send the DHCP packet to this IP address.

   -h client-hardware-address
        Use this hardware-address in the DHCP request. It can be up to sixteen octets seperated by colons (i.e. 01:02:03:04)

   -g gateway-IP-address
        Use this IP address for the gateway IP address in the DHCP packet.  This option is currently broken

All the best!

+Daniel.

Answer 2

This is an old thread but for all its worth, my vote goes to http://blog.thecybershadow.net/2013/01/10/dhcp-test-client/ From the blog:

While trying to set up my home network, I was dismayed that there was no simple way to test the DHCP server. Snooping packets is limited to examining existing traffic.

DHCP test tools exist (DHCPing and dhquery), however, both are outdated and don’t work with the latest versions of their requirements, and both won’t work on Windows.

I’ve written a simple DHCP “client” which can receive and decode broadcasted DHCP replies, as well as send out DHCP “discover” packets. The tool is cross-platform and should work on Windows and major POSIX systems.

I've downloaded it from https://github.com/CyberShadow/dhcptest and compiled it. He provides compiled versions for windows but on Linux you have to compile it yourself which is very easy with good instructions.