Caltech IP Address Guide

Caltech IP Address Guide

DHCP Addresses

CITnet (the campus wired ethernet network) is DHCP-enabled on most subnets. This is done to facilitate connection to the network for all users in the Caltech Community. If at all possible, please use DHCP for your IP address needs.

Important Notes

  • DHCP Servers on CITnet that interfere with the IMSS run DHCP Servers will be considered rogue and blocked from network access.
  • DHCP Servers run by local systems administrators which have prior approval from IMSS are acceptable.
  • DHCP addresses will not be assigned hostnames.

  • DHCP addresses are not to be entered into devices as a static IP address. This causes problems for DHCP clients and the devices improperly using the DHCP addresses in a static manner will be blocked from CITnet until the problem(s) are resolved.

Static Addresses

  • Do not borrow or steal an IP address; if one is needed, contact Hostmaster and one will be issued.
  • Blocks or ranges of addresses will not be issued.
  • There may be instances where a DHCP address may not be recommended for use with a device connected to CITnet. If this is the case, please contactus at (request type IMSS-->Network, Wireless & Remote Access-->Host and Address Requests)with the following required information.
  • Due to limited address space at Caltech, Virtual Hosts (secondary interfaces for the same computer/device) will not be issued separate IP addresses for the same device. IMSS will assign multiple hostnames to the same physical device.

Required Information to Request a Static IP Address

  1. Name of Responsible Party (RP) using the IP address/Name of the systems administrator
  2. Building and Room where the device is connected to CITnet
  3. Phone Number of RP (optional)
  4. RP's Caltech Email Address (preferably your email address)
  5. Desired Hostname to be assigned to the device.
  6. Mail Exchange Information (optional)

Please follow the instructions at How To Check For Available Hostnames to determine if the desired hostname is available, and read over Domain Name Services Provided at Caltech for Hostname issues. We will make every attempt to use the hostname you provide as long as it is not already in use.

Naming Conventions

A Static Address must have a hostname assigned to it. Please refer to the section of Domain Name Services Provided at Caltech for additional information.

Renewal of Addresses

At this time, we are not requiring a renewal of Static Addresses. However, unused addresses will be reclaimed.


Static IP Addresses not in use for a period of 2 months will be reclaimed unless a prior agreement has been made between the RP and Hostmaster. We request that when the RP leaves the Caltech Community, the RP notifies IMSS to facilitate the cleanup of our records.

Static addresses that have not been assigned a hostname will be reclaimed and blocked from the network. All attempts will be made to contact the RP prior to denying CITnet access.

IP Address Configuration Guides

Click on the right-hand menu for guides.