Network connection problems for moveable computers.
Why won't my computer work on the Branner Library network?
How do I make my computer connect to the network in non-Earth Sciences
buildings?
Why do I lose my wireless connection when I take my laptop from
Geology Corner to Mitchell?
Last revision July 3, 2007
To use the network, your computer must have a known and unique
IP address that is
valid for the network to which you have connected.
This set of questions all relate to problems getting such an address
when you move your computer from its normal "home" wired network connection.
When you
register your computer
on the Earth Sciences wired network, a unique static IP address is assigned
to that computer.
When
configured correctly,
that assigned IP address is provided automatically
to your computer by the campus
DHCP servers whenever it connects to the network.
This IP address is only valid on the Earth Sciences network.
To access the wired campus network outside Earth Sciences, you must register
your computer with the
roaming attribute,
so the DHCP servers can give it a temporary IP address valid for
that other part of campus.
The Branner Library is
not
part of the Earth Sciences wired network,
even though it is housed in the Mitchell Earth Sciences Building.
So, to use your computer on jacks in Branner Library, you must register with
the roaming attribute.
Similarly, when you access the
wireless network,
the DHCP servers will give your computer a valid temporary IP address.
The wireless network is always "roaming"; you never have a
static IP address there.
You must
register your wireless card
in order to get DHCP service.
Furthermore, the wireless network is divided into multiple zones,
each with a different range of valid temporary IP addresses.
If you move from one zone to another, your computer needs
to ask the DHCP servers for a new address.
The three Earth Sciences buildings are
not
in the same wireless zone.
Geology Corner is in the Main Quad zone, Mitchell (except Branner
Library) and Green
Earth Sciences are in the Quad 4 zone, and Branner Library on
the second floor of Mitchell Building is in the Library zone.
How to solve these connection problems.
First of all, make sure that your computer is properly registered
and configured. If you missed any of these steps, contact the
network manager.
Next, learn how to "renew your DHCP lease".
Your computer acquires its IP address, whether it be the normal
one for Earth Sciences, or a roaming or wireless one, by contacting
the DHCP server, which supplies a "lease" on that IP address that
is good for a specific amount of time.
The problem is that your computer may not realize that it has been
moved to a new network and needs a different IP address. It may
have plenty of time left on its original DHCP lease and keep trying
to use that old IP address, which is no longer valid in the new location.
Modern laptops, particularly those from Apple, are generally very
good about noticing when they are connected or disconnected from
a wired network, or when they are put to sleep and re-awakened while
using wireless. In that case, they automatically contact the DHCP
sever again to verify or get a new IP address.
But not all computers work that well. If you move your properly
registered and configured computer to another network (or another
wireless zone) and it does not work on that network, you need to
force it to contact the DHCP server again. This is called "renewing
your DHCP lease".
How to renew your DHCP lease.
Windows 2000, XP, or Vista
-
Open a command prompt window (Select
Run
from the
Start
menu, then type in
cmd
and press the RETURN key).
-
In the command prompt window, type this command
(don't forget to press the RETURN key):
ipconfig /release
-
Now, type this command (and press the RETURN key):
ipconfig /renew
-
Close the command prompt window.
Mac OS X
-
Open the
Network
System Preference Pane.
-
In the
Show:
drop-down menu, make sure that the connection method you are
using is selected, for example,
Built-in Ethernet
for normal wired connections, or
Airport
for wireless.
-
Make sure the
TCP/IP
tab is selected.
-
The
Configure IPv4:
drop-down menu should be set to
Using DHCP.
Fix it if needed.
-
In Mac OS X versions 10.4 and 10.3, there will now be a
Renew DHCP Lease
button below and to the right of the
Configure IPv4:
drop-down menu. Click on that button.
-
Older versions of Mac OS X may not have the
Renew DHCP Lease
button. They may also
have the name
Configure:
for the drop-down menu.
For these older versions, click on the
Apply Now
button on the bottom of the page.
If that button is not available (grayed out), then
first reset the
Configure:
drop-down menu to the
Manually
option and then back again to
Using DHCP.
Now the
Apply Now
button should be available. Click it.
-
After a few seconds, a new IP address should appear.
-
Close the
Network
System Preference Pane.
Legacy operating systems
See this page
for information on how to renew a DHCP lease for some older
operating systems that are no longer supported on the Earth Sciences
network.
