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I would like to verify a dhcp server configuration, i.e. if a client gets the correct DNS server, domain name, etc. I have a working DHCP setup, and a computer with a static IP address from which I can send DHCP requests to the DHCP server.

I am looking for a library (or program) to request a lease and dump all the information.

So far I have seen:

  • dhcping -- works, but doesn't write out the lease it received
  • pydhcpd -- not developed, alpha (?)
  • pydhcplib -- no documentation, not sure if it can actually send packages or is just the encapsulation; The dhquery should work based on this library and claims to do partly what I want, but after fixing an API change on client.SendDhcpPacketTo it doesn't receive any response.

Is there any existing script or library that can print or receive the DNS information the DHCP server sends out? Any language is acceptable (Perl? Java?).

Ultimately, I would like to put that into a Nagios check script.

j13r
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1 Answers1

7

I just forked dhclient, creating dhcprobe

Using DHCProbe, one can request a lease from a DHCP server, and dump the result for verifying the configuration.

Example in verbose mode:

 $ sudo ./dhcprobe -v -s 172.20.205.1
Got answer from: 172.20.205.1
option 53 DHCP message type 6 (DHCPNAK)
option 54 Server identifier 172.20.205.1
option  1 Subnet mask 255.255.255.0
option  3 Router 172.20.205.1
option 15 Domain name slh.local
option  6 DNS server 172.20.200.250
option 51 IP address leasetime 
option 58 T1 
option 59 T2

This allows verifing that the domain name, DNS server, etc. are configured correctly in the DHCP server.

Source and Info here: https://github.com/JohannesBuchner/DHCProbe

j13r
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