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SCS IP Reallocation

About

SCS Computing Facilities is in the process of reallocating our IP address space. The purpose of this reallocation is to prepare the appropriate IP address space for SCS computers that will be located within the new Gates Technology Center. This reallocation will also allow us to use the features of IP routing more effectively within SCS.

The reallocation of IP addresses will mean that many computers within SCS will have their IP address renumbered. The renumbering of IP addresses will be done in small blocks over the next two years. The new IP address assignments will be based on the physical location of the computer.

Most computers in SCS are currently using DHCP to obtain their IP information. For most computers using DHCP, the renumbering process will be accomplished by a simple reboot of the computer. The reboot will cause the computer to obtain the new IP address and trigger an update of the DNS records. The computer should have full network connectivity once the reboot is complete.

Users whose computers can not obtain their new IP address via a simple reboot will be contacted to schedule a time when either their computer will be configured to use DHCP or when their computer will have the new IP address manually configured. Computers that fall into the following categories will require some manual intervention in order to accomplish the renumbering:

  • Computers not configured to boot via DHCP
  • Computers that can not be configured to boot via DHCP
  • Computers with multiple IP addresses on the same network segment
  • Some computers with multiple hostnames

Users that have web applications, databases, or other software that reference computers by IP address should consider changing these references to use the computer's hostname. Please notify SCS Facilities if you are using a software package that does not permit references by hostname.

Users that maintain a custom version of /etc/hosts or other hostname/IP address tables should be aware that the upcoming renumbering may affect entries in these tables.

Note: We strongly recommend that all computers that can use DHCP to obtain their IP information be configured to do so.

How It Will Work

Users will be notified via email two weeks before their scheduled renumbering period begins. Users should notify SCS Facilities by sending mail to help@cs.cmu.edu or by calling the SCS Help Desk at x8-4231 within these two weeks if there is a reason why their computer can not be renumbered at this time.

Users will be notified again via email immediately before the time period for renumbering their computer begins. The renumbering period will be a two week time frame during which users will need to reboot their computer to install the new IP address. Users who have not performed the reboot after 1 week will again be notified via email. A final notice will be sent one day prior to the end of the renumbering period to any users who have not rebooted their machine and installed the new IP address.

Please note that unless other arrangements have been made, any machine which has not been rebooted by the end of the renumbering period will at a minimum experience a disruption of active network connections and potentially complete network loss is possible until the machine has been rebooted.