What is DHCP?
Dynamic Host Configuration Protocol (DHCP) is a method for
configuring Internet Protocol (IP) network interfaces dynamically. A
DHCP client does not require the user to configure an IP address,
subnet mask, etc, on his computer, but rather receives these data
from a DHCP server. It allows for a much easier user setup, more
versitile network management, and easier support for mobile computers.
DHCP is a standard protocol, defined in
RFC 2131.
How is Virginia Tech using DHCP?
Since Fall 1999, DHCP has been used as the default method for
configuring user computers in the Virginia Tech residence halls. To
use DHCP, a user need only configure his computers to use DHCP, which
in many operating systems is a single check-box. The VTNet setup will
configure this for users who wish to use it.
Users and network liaisons from academic and administrative
departments may find these more specific
notes useful.
Do I need to register?
Any user may register his Ethernet card's hardware or
"MAC" address with the DHCP server. (The term "MAC
address" is from the Media Access Control protocol of Ethernet,
and has nothing to do with the Apple Macintosh.)
This registration is required for
anyone who would like to use roaming
DHCP (public portal) access. It is important to note that CNS does
not provide the portals for public access, but rather works with the
sponsoring department to manage the IP address assignment method.
To register your Ethernet card for roaming access
log in to the MAC address registration web page with your PID and
password. Note: as of this writing (11/7/2000), there are few
supported campus public portals; however, this is a planned feature,
and does require registered Ethernet cards. Eventually there will
likely be roaming access in all parts of the Virginia Tech campus, with
this service initially available in Torgersen Hall (planned Spring
2001).
Note that the registration process associates your PID to your
Ethernet card, so if you change Ethernet cards you will have to change
your registration. This can also be done on the
MAC address registration web page. At this time there is no
mechanism for a non-Virginia Tech affiliate to register his Ethernet
cards.
If you have exchanged Ethernet adapters with someone who has already
regsitered that adapter, the previous owner may need to unregister the
card before you can register it.
Residence Hall Reserved IP address assignment
There is no support for static IP assignments in the residence halls
at this time.
What about hostnames?
If you receive a dynamic IP address, the DNS server will have an
arbitrary domain name associated with your address. This will allow
you to use servers that require domain names, and for most users this
is all that is needed.
How do I see what IP address, etc, I got?
To see what IP address, etc, you recieved from the DHCP server:
- Windows 95/98: winipcfg
- NT: ipconfig
- Mac: TCP/IP Control panel
- Unix: varies. ifconfig <interface> or
ifconfig -a almost always works, but there are some dhcp
commands that are platform-specifc for more DHCP-specific info.
The router or gateway should always be the ".1" host in
your subnet (e.g., if your address is 198.82.75.34, your gateway should
be 198.82.75.1). If it isn't, there may be a serious security problem,
and you should call 4-Help or 1-6780 immediately.
What if I have problems?
If you encounter problems configuring your computer to use DHCP, or
have general questions, call the Information Systems Help Desk at
4-HELP (or 231-HELP). If you know that your computer is configured
properly and are having difficulty getting a response from a DHCP
server, call the Network Operations Center at 231-6780.
As a first step, try releasing your address, then renewing; this is
done with winipcfg under 95/98 and ipconfig under
NT. If this works, and you consistently do not get a response from the
DHCP server until you manually go through this, then your Ethernet card
is not getting on the network in a timely manner. This can be caused
by a number of reasons, but one common reason you can check is that
your Ethernet card is set to autosense the speed and duplex of the
connection. Ensure that your Ethernet card is set to 10Mbps,
half-duplex. If you need any assistance with this, check your Ethernet
card documentation or call 4Help.
