Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm writing a cut-down DHCP server implementation for a specific use-case. Rather than split off onto a private network for the development I'm running the server on a custom port (11167) and sending to a custom port (11168).

In order to test the system without needing access to the embedded client I'm using Ubuntu 11.04 running in Virtual Box.

I'm wondering how I can get dhclient on the Ubuntu box to talk to port 11167 and receive on port 11168.

share|improve this question
up vote 1 down vote accepted

From the dhclient(8) man page:

If the DHCP client should listen and transmit on a port other than the standard (port 68), the -p flag may used. It should be followed by the udp port number that dhclient should use. This is mostly useful for debugging purposes. If a different port is specified for the client to lis- ten on and transmit on, the client will also use a different destination port - one less than the specified port.

(Note this is from the isc-dhcp-client package in Debian squeeze. I don't know if your version of Ubuntu ships with a different dhclient package)

share|improve this answer
Thanks. Found this just after posting the quesion. Duh! The command: sudo dhclient -r releases any current address and stops the client. Then the command: sudo dhclient -p 11168 -d eth0 starts the client communicating with the server on port 11167 and keeps it in the foreground. Perfect! – Nick Jun 22 '11 at 9:25
PS. Can't seem to find a way of permanently changing the port using the dhclient.conf config file. – Nick Jun 22 '11 at 9:28

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.