Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

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've just landed my first job as a sysadmin, and my workplace is still using static IP adresses. Informations about adresses are kept in a textfile that is not up to date.

So, my first task here will be to set up a DHCP server.

And my question is : do you guys have any advice about how I should proceed ?

It's not a software-related question (i.e. I'm not asking what software to use and how to configure it), it's more about the right approach to take regarding IP conflicts and users not switching to DHCP.

Here's a bit of context:

  • I'm in a small science lab (about 100 users with their boxes)
  • Users are admin on their machines
  • IP adresses are on a subnet of the university's network
  • Servers are UNIX/LINUX, workstations are Macs, Windows PCs, Linux boxes...
share|improve this question
Did you first find out the reason WHY they are using static instead of DHCP? Don't come in guns blazing trying to change things without understanding the history and getting real buy in that change is needed (in this case going to DHCP) before implementing something. – TheCleaner Jan 13 '14 at 13:58
I did. The sysadmin I'm replacing actually advised me to switch to DHCP. He was frank about why he hadn't done it before : he didn't want to bother doing it. He's retiring this year and focused more on his teachings than his administration tasks during his time at the lab. So, no specific reason. Edit : The need for dynamic adressing is justified by the fact that the lab is often visited by guest, students, and members from another site who come with their devices. – iodbh Jan 13 '14 at 14:11
up vote 0 down vote accepted

By no means exhaustive, but some of the points I would go through:

  1. Gather information about the current setup, either by manual audit or automated network scanning tool (make sure you have permission to run said tool)
  2. Capture current static IP addresses and MAC addresses of all affected machines
  3. Make sure your lab LAN is suitably separated from the main network, e.g. by VLAN, so the DHCP broadcast traffic does not interfere with servers not in your control
  4. Install and configure the DHCP server to the best of your abilities/research
  5. Document the DHCP server installation/configuration and the process for adding new reservations
  6. Define the IP/MAC pairs found in #2 as reservations in the DHCP scope; document with user information
  7. Inform userbase of the requirement to change to DHCP; specify dates/times that you will be changing the servers, provide instructions to the end-users as to how to configure their own machines (and how to rollback) and provide days that you will be available to assist/troubleshoot
  8. Change the configurations (Puppet, Group Policy, manually) of the devices in your direct control
  9. Use your DHCP server's tools to confirm the reservations are becoming active and the IP addresses are getting allocated correctly
  10. Chase up stragglers until all reservations are active and correct
  11. Allocate new reservations, based on MAC address, as and when new devices are commissioned.
  12. Update your lab's end-user documentation to include how to access the 'new' network

(You may be able to get away without reservations for all your end-users -- although your servers should certainly be reserved -- but you making the assumption there that your end-users haven't created a spiderweb of cross-dependencies to each others' machines so, unless you are explicitly re-designing the subnetting/IP allocation, I would put the existing IPs in as reservations, for all known devices, and allocate reservations to all new ones as they come in)

share|improve this answer
This is very helpfull. Scanning the network and using the results to prepare reservations were the steps I was missing. Thank you for taking the time to share you advice. – iodbh Jan 15 '14 at 13:30

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.