The term, I believe, is black-hole router.

----- Original Message -----
From: "Ben Schorr" <[EMAIL PROTECTED]>
To: "Exchange Discussions" <[EMAIL PROTECTED]>
Sent: Tuesday, March 19, 2002 9:54 PM
Subject: RE: Some "Hosts Unreachable" - Follow-up


> Well, the problem is resolved but nobody's entirely sure how.  It looks
like
> it was an issue with a router somewhere upstream discarding improperly
sized
> packets instead of responding properly (Q136970 is sort of related) but
> whose router and what they did to fix it we don't know for certain just
yet.
>
> What a day.
>
> -Ben-
> Ben M. Schorr, MVP-Outlook, CNA, MCPx3
> Director of Information Services
> Damon Key Leong Kupchak Hastert
> http://www.hawaiilawyer.com
>
>
> > -----Original Message-----
> > From: Ben Schorr [mailto:[EMAIL PROTECTED]]
> > Sent: Tuesday, March 19, 2002 1:00 PM
> > To: Exchange Discussions
> > Subject: Some "Hosts Unreachable"
> >
> >
> > This is a new one on me; maybe some of you have seen it
> > before.  Exchange 5.5 on NT4SP6a using the IMS to connect
> > through an ISA server.  On a handful of hosts the message
> > queues up with a "Host Unreachable" error.  On most hosts
> > (including old favorites like aol.com, hotmail.com, etc.)
> > mail comes and goes just fine and we don't seem to be having
> > any problems RECEIVING mail.
> >
> > But to this small band of hosts (including hawaii.edu and
> > hawaii.rr.com) the mail just queues up.  Here's a snippet
> > from an SMTP log that may shed some
> > light:
> >
> > 3/19/02 12:15:06 PM : >>> MAIL
> > FROM:<[EMAIL PROTECTED]> SIZE=1977 RET=FULL
> > 3/19/02 12:15:06 PM : <<< IO: |250 2.1.0
> > [EMAIL PROTECTED] OK
> > |
> > 3/19/02 12:15:06 PM : <<< 250 2.1.0
> > [EMAIL PROTECTED] OK
> > 3/19/02 12:15:06 PM : >>> RCPT TO:<[EMAIL PROTECTED]>
> > NOTIFY=FAILURE,DELAY
> >
> > 3/19/02 12:15:06 PM : <<< IO: |250 2.1.5 [EMAIL PROTECTED]
> > |
> > 3/19/02 12:15:06 PM : <<< 250 2.1.5 [EMAIL PROTECTED]
> > 3/19/02 12:15:06 PM : >>> DATA
> >
> > 3/19/02 12:15:06 PM : <<< IO: |354 Start mail input;
> > end with <CRLF>.<CRLF>
> > |
> > 3/19/02 12:15:06 PM : <<< 354 Start mail input; end
> > with <CRLF>.<CRLF>
> > 3/19/02 12:16:22 PM : 499 Host unreachable: cta.net.  Message
> > subject: ""Plain Text Test"".  Rescheduling delivery for later.
> >
> > Notice that it seems to be going fine until it gets the 354
> > message, then it sits for a little over a minute and seems to
> > time out.  This particular test message was just a couple of
> > lines of plain text; so it shouldn't be a size issue.
> >
> > We've already restarted the IMS several times and the entire
> > Exchange server once.  Judging by the oldest message in the
> > queue this problem seems to have started this weekend and no
> > unusual system maintenance or changes occurred over the
> > weekend.  As far as I know we were able to send mail to/from
> > those domains just fine on Friday.
> >
> > Baffling.  Any thoughts on what might be causing this and how
> > we can resolve it?
> >
> > -Ben-
> > Ben M. Schorr, MVP-Outlook, CNA, MCPx3
> > Director of Information Services
> > Damon Key Leong Kupchak Hastert
> > http://www.hawaiilawyer.com <http://www.hawaiilawyer.com>
> >
> >
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