Tuesday, October 1, 2002

Network Manager Challenge: solving Exchange’s requesting data problem


By David Gewirtz

A few weeks ago, we issued the Network Manager Challenge. For those of you who might not recall the details of our challenge, here's a recap. We had an offsite machine that was constantly stuck attempting to get mail from the Exchange server, giving us the message "requesting data from Exchange server" but not doing anything more productive. We'd run out of ideas after uninstalling and reinstalling office, cleaning the registry, reinstalling the network drivers, and so forth, so we opened it up to our readers.

Our winner for this week's Challenge is Geoff Mason of ITS WorkGroup Services, whose answer "I'm wondering if the problem you described is a Black Hole Router issue" turned out to be the fix we needed.

According to an obscure Knowledge Base article that Geoff forwarded to us, with a TCP/IP-based wide area network, communication over some routes may fail if an intermediate network segment has a maximum packet size that is smaller than the maximum packet size of the communicating hosts -- and if the router does not send an appropriate Internet Control Message Protocol (ICMP) response to this condition. Such a router is sometimes known as a "black hole" router.

Basically, you have to go in and hack your registry (never for the faint of heart) and tweak the packet size. It's all described the article #Q314825. To read it, go to http://support.microsoft.com, select Knowledge Base, and enter the Q-number listed.

Be very careful when you do this. Backup your registry first. If you break your system, don't come cryin' to us.

We followed the instructions and our problem disappeared. Nice job, Geoff. As prizes for this fabulous accomplishment, Geoff wins bragging rights, the admiration of his peers, and the ZATZ Solutions Guide of his choice.

We did have other contributors, and their ideas might also prove useful to those with this problem.

Fred Stoki asked if the user was using a personal firewall (no), or an email virus scanner that checks email as it's being pulled down. We are using Norton AntiVirus, but turning it off didn't solve the problem. Both were good suggestions, though.

Diego Zenizo wrote "We solved a similar problem by upgrading BOTH the Linksys router AND the DSL modem (Alcatel in our case) firmwares to the latest version. There seems to be some TCP dialog 'similar' to a FTP session going on, and the router was not listening to the response, so the request is actually waiting there forever. This is loosely discussed on the Linksys firmware upgrade release notes. Somehow, we needed to upgrade both devices for this to work."

Andrew Martin suggested "Have you tried removing and re-instating the Microsoft Exchange Server service (Tools->Email Accounts->Next) to resolve the Exchange access issue?"