We have been getting random 502 errors for a while now and it has been
very difficult to track down. Last week I noticed something by accident
that has shed a lot of light on the problem. From the BM DNS Status
screen you can see the current status of the DNS resolvers configured
for the server. Fairly regularly the 1 DNS server will show as down. It
stays down for about 45 seconds then comes back up. While it is showing
down DNS request will not resolve and the workstations get a 502 error.
As far as I can tell the DNS requests are not being sent to the 2nd or
3rd DNS server listed when the 1st is flagged as down.

Here's a little info on my setup. We have 2 DNS servers inside the
firewall on a 192.168.X.X network. One is Netware 6.5sp2 and one is
Netware 6.0sp3. The Netware 6.5 DNS server is the only one listed in
resolv.cfg on the Bordermanager but I see the same issue if I change the
resolv to the 6.0 server. The 2nd and 3rd DNS listed in resolv are
upstream DNS servers hosted by our ISP. The 6.5 server is running the
named.nlm from the 6.5sp3 beta patch.

Bordermanager is 3.8 with all the current patches. Proxy.nlm is version
4.02.10 (Jan11, 2005) The server is also Netware 6.5 fully patched with
the addition of the most current TCP patch (beta).

I have been trying to capture the data that occurs just as the DNS is
flagged down but since it is so random I haven't been able to log is
just yet. I can look at the communications that occur while it is
flagged down and it shows the BM server IS making DNS requests and the
DNS server IS responding but the number of requests is vastly different
than "normal".

While there is no pattern to when it will go down, it does appear in
roughly 10-12 minute intervals for a few hours at a time. Yesterday it
was down often from around 8:00 to 9:30 then was fine for a few hours
and started going down again later in the day.

Also, if I list both of my DNS servers in the resolv only the 1st one
will show as down. If I flipflop the addresses it will still only show
the 1st one listed as going down. However on 2 occasions yesterday all
3 DNS servers showed as down.

Does anyone have a suggestion on what I can do to fix this? I have tried
everything I can think of at this point.

Buster Flynn
Sevier County Schools