Ask SIPB - September 23, 2003
Having problems connecting to the network since Thursday, September
11? Getting deluged with lots of spam? This week, we explain the
required re-registration for dynamic IP addresses (DHCP) and e-mail
etiquette.
Who was affected by the DHCP reregistration?
DHCP is the network protocol that allows users to automatically obtain
an IP address, connect to the network and have various network
settings configured automatically. Everyone who was using hostless
(dyn-o-reg) DHCP was required to re-register for it as of 8 PM on
September 11. People using static IP addresses or host-based (dhreg)
DHCP registration were not affected. For more information about the
differences between these, please see our August 24 column at http://www.mit.edu/~asksipb/2003columns/2003-08-24-connectnet/.
If you are a student and you don't know what a static IP address is,
you probably don't need one and are using hostless DHCP. Faculty and
staff are likely using a static IP address or host-based DHCP, because
hostless DHCP is not available for faculty and staff.
Why do I have to reregister for DHCP?
As of 8 PM on September 11, all DHCP registrations were cleared.
Because of the recent slew of Windows vulnerabilities and the number
of machines that have been compromised, I/S is trying to ensure that
all Windows machines have port filtering turned on, in order to
pre-emptively prevent future worms from infecting MIT machines.
Unfortunately, reregistration is required for all registered systems,
even non-Windows machines.
I tried reregistering for DHCP, but it didn't work!
Because everyone was forced to reregister for DHCP at the same time,
the registration server was overloaded. In some cases, it did not
respond quickly enough to assign registration (net 10) IP addresses to
computers. In other cases, computers received an address, but the
registration itself proceeded slowly, taking 15 minutes instead of the
usual 30 seconds.
Now that most people are reregistered, things have mostly returned to
normal. In some cases, however, students have registered for DHCP
properly, but are still unable to get a real net 18 IP address, even
after waiting a day after registering.
If you continue to have problems in a dorm, please contact an RCC by
submitting a help request at http://rcc.mit.edu/. For non-dorm
problems, contact the Computing Helpdesk at computing-help@mit.edu,
x3-1101, or in N42.
How do I reregister for DHCP?
If you have a non-Windows machine, open up a web browser and go to any
web site. You will automatically be brought to the DHCP registration
page. Simply follow the instructions and enter your username and
password when requested.
If you have a Windows 2000 or XP machine,
however, you will be instructed to enable TCP port filtering.
Instructions will be given when you attempt to reregister. You can
also find them online at
http://web.mit.edu/net-security/prevent-reinfection.html.
When using port filtering, please ensure that you are filtering TCP
only. Filtering UDP or ICMP will prevent some services from working
properly. After enabling filtering, you can finish registering.
I want to send mail to lots of people. Should I do so?
Before doing so, consider whether your email is on-topic for the lists
you wish to email. Mass emailing a large number of lists, such as all
the dorm lists, is unacceptable if what you are mailing is not
relevant for the lists. While your email will certainly be read by a
large number of people, they will be annoyed and unlikely to be
favorably inclined towards you.
Also, keep in mind that you generally should not send mail to a list
you aren't subscribed to, unless it is a list designated as one where
others can post, such as reuse.
What should I take note of when replying to mail?
When replying to an email, check to see to whom your reply will be
sent. You may be sending email to a lot of people who don't need to
see your reply, especially since what looks like a single email
address may be a mailing list to which many people subscribe. For
example, if a person sends out an invitation to an event and asks the
recipients to let him know if they are going, it is inappropriate to
CC the whole list in response. In this case you should use the
"Reply" command instead of "Reply to All" in your mail program.
On the other hand, when e-mailing lists such as sipb@mit.edu,
where you are asking for help, you should continue to keep the list in
the To: or CC: line so that other people can continue to make
suggestions and help you. You can do so by using "Reply to All."
When replying to a long email, especially on mailing lists, avoid
including all of the text of the other person's email only to add "me
too" at the bottom.
Should I forward this email?
Do not forward chain letters. This includes email that claims 50,000
email signatures are required to help someone as well as email that claims
something good or bad will happen if you do or don't forward the email
along. Many so-called "helpful advice" email, especially when written
in a sensationalistic tone, are nothing but hoaxes. The Urban Legends
Reference Pages, http://www.snopes.com/, can help identify common hoaxes
and tall tales.
I want to subscribe to this list. I should email it, right?
NO! Emailing lists asking to be added will get the list
members annoyed at you, because generally, they don't care that you
want to be added and can't do anything anyway. The same is true of
unsubscribing.
You can remove yourself from MIT mailing lists using a variety of
tools that are part of the Moira database management system.
mailmaint is a menu-driven tool; more convenient is
blanche. Use
athena% blanche listname -d username
to remove yourself from a list. For more information on how these
commands work, please see our November 22, 2002 column at http://www.mit.edu/~asksipb/2002columns/2002-11-22-mailinglists/.
Alternatively, you can use the web interface at http://web.mit.edu/moira/.
If you're having trouble removing yourself from an MIT mailing list,
you can e-mail the administrators of the list at
owner-listname@mit.edu or listname-request@mit.edu, who
will be able to help you. You should not send your request to the list
itself; our servers do not intercept subscribe and unsubscribe
requests, and sending a subscribe or unsubscribe request to the list
is useless, as most people will be unable to do anything to actually
process your request. For non-MIT mailing lists, check for an
unsubscribe address in the email text, or try
listname-request@example.com, where example.com
is the domain where the list is hosted.
To ask us a question, send email to sipb@mit.edu. We'll try to answer you
quickly, and we can address your question in our next column. You
can also stop by our office in W20-557 or call us at x3-7788 if you
need help. Copies of each column and pointers to additional
information are posted on our website: http://www.mit.edu/~asksipb/