Strange DNS behavior

Trond Endrestøl Trond.Endrestol at
Thu Oct 26 16:51:22 UTC 2017

On Thu, 26 Oct 2017 08:10-0700, Chris Maness wrote:

> I have been running my own DNS for years with glue records and the whole
> nine yards.  A couple of days ago (without warning) my DNS server stopped
> resolving requests external to my local network.  If I portscan my server
> from outside my local network, I see that TCP port 53 is open.  I can use
> dig to resolve any host on that server as long as it is local, but if I try
> to to use dig from a remote host.  It just times out.  I thought I might
> have been hacked or something, but it does not appear that the named.conf
> file has been changed since 2015 (according to the stamp).
> Any suggestions as to what could be the issue?

Here are some very basic suggestions.

As you probably know, DNS uses UDP and switches to TCP if it receives 
a truncated response or is told to do TCP right from the beginning.

Make sure your ISP hasn't blocked UDP and TCP port 53 in your 
direction. Check your own packet filter/firewall just to be safe.

You can restart your DNS server process, you'll lose whatever's in the 
cache, but that shouldn't matter too much.


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