Caltech
Information Management Systems and Services
IMSS  /  Services  /  Wired, Wireless & Remote Access  /  Trouble Shooting & Tips  /  Student House Network Services

Broad Center Network Services

The student house networking project at Caltech has made available a 100baseT ethernet port for every resident in the on-campus houses (the North and South undergraduate house complexes, the Avery house complex, Marks/Braun and the Catalina Housing Facility).

Each room has one port per occupant. Basic configuration details are provided to residents on a sticker which should be on the wallplate containing the port. The wallplate label sticker should have all the information students need to connect their computer to the network; a general version of this information and some additional details are provided below.

Be sure to familiarize yourself with the Network Policy.

Some Useful Definitions

IP
Internet Protocol, a specification for computer communication.

IP address or IP number
A dot-separated set of numbers, such as 131.215.138.42, which corresponds to a computer.

URL
Uniform Resource Locator, a string of characters describing method, a host name, and a document name, for retrieval of information. Accessed with World Wide Web browsing programs.

IMSS
Caltech's Information Management and Systems Services department.

House Rep
IMSS student employee who acts as your liason with IMSS and is the primary contact for computer troubleshooting in your house -- see Help Contacts page.

Physical Network Connections

To use the network port, you must have a computer with an Ethernet card. If you need help selecting an Ethernet card or configuring your TCP/IP software, check out our configuration guide pages or contact your house rep.

Your connection is wired with 100baseT. This looks something like a wide phone jack. However, note the following:

  • You cannot use a telephone cable to connect your computer to the wall jack. You will need a 100baseT Category 5 patch cable, available from the Caltech Wired or any other computer store.
  • Never connect your computer's network port to a phone jack -- telephone jacks transmit voltages that could damage your Ethernet card or computer.
  • In Avery, wallplates may include both network and telephone ports which will look almost identical. Be sure to plug your computer into the network port, which should have the words "CAT 5" in very faint raised lettering on the jack.

IP Address Assignment

The North Houses, South Houses and Temporary Housing Facility used during South House Remodeling are connected to the Campus Network. All computers at these locations can use DHCP to obtain a valid IP address. If an occupant needs a static IP address, please submit a request at http://help.caltech.edu (request type IMSS-->Network, Wireless & Remote Access-->Host and Address Requests)with the required information.

The Student House Network Port/Room/IP Address Mapping Database is no longer valid since new subnets have been assigned to the Student Houses.

Caltech IP number conventions

In all fields, the numerical values for the subnet and host will depend on your location.

Type Value IP address 131.215.subnet.host Router/Gateway address 131.215.subnet.254 Broadcast address 131.215.subnet.255 Subnet mask 255.255.255.0 Domain Name Server addresses 131.215.9.49, 131.215.139.100, 131.215.254.100

Most computers allow you to list more than one IP nameserver. Feel free to enter the three listed above in random order.

On Macintosh computers with MacTCP (Mac OS 7.5.x and older) the nameserver entries should look like:

Domain IP address

caltech.edu: 131.215.9.49
. 131.215.9.49
. 131.215.139.100
. 131.215.254.100

Yes, with "." in all but the first row and yes, with the first IP address listed twice (once with domain caltech.edu and once with domain ".")

This configuration is not correct for Macintosh computers with Open Transport (Mac OS 7.6.x and higher). If your computer has Open Transport (indicated by the existence of a "TCP/IP" control panel instead of a "MacTCP" control panel) each nameserver should only be listed once.

What is my "default" router or gateway?

IMSS managed networks use host "254" as the default router.

What is my "broadcast" address?

This number will be host number "255" on your subnet. For example, if your address is 131.215.4.16, your broadcast address will be 131.215.4.255. Many computers do not use or allow you to configure a broadcast address. Do not worry if you do not see a place to configure this information.

Can I hook up a hub and additional computers?

Yes, you may hook up a hub to the port and get addresses for additional devices (printers, computers, etc.). Please do not connect more than one hub.

Must I change my IP address to use the port in the house lounge?

Lounges and libraries with available network ports may be used by the occupants. Note that not all public areas are on the same subnet as the house. If you are temporarily connecting a computer which already has a valid IP address on the same subnet, no action need be taken. If public port is on a different subnet, use DHCP to obtain a valid IP address for that public port.

So, does that mean I can use any address I want?

No. You must not randomly choose IP addresses. If you need an IP address, use DHCP or submit arequest at http://help.caltech.edu (request type IMSS-->Network, Wireless & Remote Access-->Host and Address Requests)for an IP address.

Never just randomly choose a TCP/IP address. Never assume that because an address does not respond to pings that it is "free". Some computers do not answer pings or may be briefly turned off.

Computers that are in conflict with properly registered IP addresses (DHCP or static) will be blocked from accessing network resources until the misconfiguration is corrected.

How do I register a name for my computer?

Read the information about IMSS DNS Service at Caltech and the Caltech IP Address Space page, and then follow the instructions there.