Frequent timeout

[John W. Blue]

tcpdump is your newest best friend to troubleshoot network issues.  You need to see what (if anything) is being placed on the wire and the responses (if any).  My goto syntax is:

tcpdump -n -i eth0 port domain

I like -n because it prevents a PTR lookup from happing.  Why add extra noise?  As with anything troubleshooting related it is a process of elimination.

Good hunting!

John

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________________________________
From: Alex <mysqlstudent at gmail.com>
Sent: Friday, August 31, 2018 4:20 PM
To: bind-users at lists.isc.org
Subject: Frequent timeout

Hi,

Would someone please help me understand why I'm receiving so many
timeouts? This is on a fedora28 system with bind-9.11.4 acting as a
mail server and running on a cable modem.

It appears to happen during all times, including when the link is
otherwise idle.

31-Aug-2018 16:52:57.297 query-errors: debug 2: fetch completed at
../../../lib/dns/resolver.c:3927 for support.coxbusiness.com/A in
10.000171: timed out/success
[domain:support.coxbusiness.com,referral:2,restart:4,qrysent:5,timeout:4,lame:0,quota:0,neterr:0,badresp:0,adberr:0,findfail:0,valfail:0]

31-Aug-2018 17:06:42.655 query-errors: debug 2: fetch completed at
../../../lib/dns/resolver.c:3927 for dell.ns.cloudflare.com/A in
10.000108: timed out/success
[domain:cloudflare.com,referral:0,restart:2,qrysent:13,timeout:12,lame:0,quota:0,neterr:0,badresp:0,adberr:0,findfail:0,valfail:0]

What more information can I provide to troubleshoot this?

Is it possible that even though the link otherwise seems to be
operating okay that there could still be some problem that would
affect DNS traffic?

I've also clear all firewall rules, and it's not even all queries which fail.

Thanks,
Alex
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