Caltech
Information Management Systems and Services
IMSS  /  Services  /  Wired, Wireless & Remote Access  /  Wired Network  /  Check for Available Hostnames

Check for Available Hostnames

Hostmaster will not issue duplicate hostnames except under special circumstances, specifically transition or load balancing of servers.

In order to check to make sure that the hostname you want is not in use by another device at Caltech, it is necessary to see if there are any matching entries currently in the DNS.

Valid IMSS-Operated Caltech Nameservers are:

131.215.254.100
131.215.139.100
131.215.9.49

In order to check for existing entries, execute the nslookupcommand either on your local machine or using your IMSS UNIX (access.caltech) Account.

Before requesting a hostname, please check to see if it is available. Then submit your request at http://help.caltech.edu (request type IMSS-->Network, Wireless & Remote Access-->Host and Address Requests).

Example of Using the nslookup Command:

Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-2000 Microsoft Corp.

C:\\>nslookup
Default Server: user-ns1.mminternet.com
Address: 216.86.207.2

> server 131.215.9.49
Default Server: lukewarm.caltech.edu
Address: 131.215.9.49

> set q=any
>
> www.its.caltech.edu
Server: lukewarm.caltech.edu
Address: 131.215.9.49

www.its.caltech.edu internet address = 131.215.48.142
www.its.caltech.edu internet address = 131.215.48.102
www.its.caltech.edu MX preference = 0, mail exchanger = mail.its.caltech.edu

caltech.edu nameserver = mercutio.ni.caltech.edu
caltech.edu nameserver = nsx.lbl.gov
caltech.edu nameserver = tepid.ni.caltech.edu
caltech.edu nameserver = tybalt.caltech.edu
mail.its.caltech.edu internet address = 131.215.48.55
mail.its.caltech.edu internet address = 131.215.48.17
tepid.ni.caltech.edu internet address = 131.215.254.100
tybalt.caltech.edu internet address = 131.215.139.100
mercutio.ni.caltech.edu internet address = 131.215.254.99
>
> my-new-host-for-caltech.caltech.edu
Server: lukewarm.caltech.edu
Address: 131.215.9.49

*** lukewarm.caltech.edu can't find my-new-host-for-caltech.caltech.edu: Non-existent
domain
> exit

Explanation of what happened above:

  1. A user has opened a DOS prompt on their local computer. It happens to be connected to the Internet via a non-Caltech ISP, and therefore is not by default using the IMSS-Operated Caltech Nameservers.
  2. That user executed the nslookup command. Not all Microsoft Operating Systems have the nslookup command. Alternatively, you can also use SSH to its.caltech.edu, log in, and then execute the nslookup command at this point using your IMSS (access.caltech) account.
  3. The nslookup command shows it is using a Non-Caltech Nameserver.
  4. The nameserver being queried is changed to an IMSS-Operated Caltech Nameserver. This is done through the server command.
  5. nslookup shows that it will now query an IMSS-Operated Caltech Nameserver.
  6. The set q=any command is executed. This is done so that any matches will return a result. It is possible for a DNS entry to be a Mail Exchange (MX) record, and without the set q=any command, such records would not show up in response to the query.
  7. The hostname www.its.caltech.edu is entered.
  8. Results of all matching entries in the DNS are shown.
  9. The user enters my-new-host-for-caltech.caltech.edu as a desired hostname.
  10. The nameserver shows that there are no matches.

Requests for hostnames that are currently entered in the DNS will be denied.

For more information on Domain Names, please read Domain Name Services Provided at Caltech and The Caltech IP Address Space.