Network issues at math.utah.edu described and resolved

[Nelson H. F. Beebe]

In mail of Mon, 26 Apr 2021 16:20:44 -0600 to these lists, I announced
https:// support for these sites at Utah:

        ctan.math.utah.edu
        ftp.math.utah.edu
        www.math.utah.edu

The next day, there were issues in reaching some of them, and that
turned out to have two causes.  

First, there was an errant firewall rule that blocked the https port
(443) from off-campus access; that was quickly fixed.

Second, and more seriously, and unknown to us in the Department of
Mathematics, campus networking staff had just replaced one of a pair
of redundant upstream routers with a new model that had route-table
inconsistencies with the old one.

The result of that hardware change was that, depending on which of the
pair that incoming traffic to the math.utah.edu domain hit, packets
would get through, or be blocked.  That reduced our traffic flow
considerably, and produced flaky network connections from both
on-campus and off-campus sites for most of Tuesday 27-Apr-2021.  My
home workstation would sometimes get through, but otherwise, would
just complain "no route to host".  The reverse connection, from campus
to home, worked fine all day.

The routing table issues have now been fixed by the campus network
staff, and we expect traffic to math.utah.edu systems to return to
normal.

The second router of the redundant pair will be replaced in a few
weeks, but at least this time, the campus network team should have
learned from the unpleasant experience of this week's router
replacement :^) [fingers crossed...]

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- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
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