[Faccus] [Fwd: Finally, good news on the e-classrooms!]

Andrea Chappell chappell at ist.uwaterloo.ca
Wed Oct 18 14:47:11 EDT 2006

The faccus mailing list complained that I had too many recipients so 
here's a re-send to just you.

-------- Original Message --------
Subject: Finally, good news on the e-classrooms!
Date: Wed, 18 Oct 2006 14:15:10 -0400
From: Andrea Chappell <chappell at ist.uwaterloo.ca>

Hello everyone,
It seems that we finally have the answer to the question "why" and a
change this morning should mean that, after the systems reboot, the
recent spate of e-classroom problems should end. (This does not
guarantee the solution to all problems, however :-)

Without going into all the details, the problem arises from a bug in
DHCP. The bug was triggered by the IST DHCP servers being set as
authoritative last Wednesday (not by the introduction of the new DHCP
server). The DHCP servers provide the correct DNS server list to the
Nexus station on the initial transaction. However, if the DHCP servers
answer a subsequent DHCP interaction (an INFORM) they send the default
or global DNS list (consisting of the two IST DNS servers) rather than
the appropriate Nexus list. The INFORM handling doesn't search for
matching host clauses (like for Nexus specific values) ... that's the
bug. [That's my explanation, and I am sure it could be improved by
someone who actually knows something about this, but I think it captures
the essence of the problems!]

Today the "Authoritative" status was removed for the IST DHCP servers
from the Nova and e-classroom subnets so that they don't provide the
incorrect list in the INFORM transactions.

Many, many thanks to everyone who helped during this crisis. Special
thanks go to Keith McGowan for remembering the same symptoms from last
December ... he even still had the old traffic data! Jason, Tim, Hon,
and Steve all devoted a lot of time to this, and I appreciate you
listening to each other's perspectives as part of the joint problem
solving effort. And, at the front lines, in perhaps the toughest
situation, being right where the problem is happening, thanks to the
e-classroom support staff, Marcel, Keith, Randy, Derek, and Viktor, for
keeping things going, under lots of pressure.

As long as tomorrow doesn't reveal more of the same problems, we should
be OK. I think that we will be reviewing the e-classroom computer set-up
in the near future, so if you want "in on" that discussion, please let
me know.

The second bit of good news is that I *think* this should be the last
email that you will receive from me on this topic :-)


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