DNS Ports

[Barry Margolin]

In article <bfhalf$1e70$1 at sf1.isc.org>,
Dave Harman <dharman1060 at earthlink.net> wrote:
>Hi, NG
>
>I am using BIND 9.2.1-16, the one that comes with RedHat 9
>I am setting up Iptables and I am having difficulty in finding out
>exactly what ports Bind uses to send and receive queries and data.
>
>I know DNS uses UDP to send and get data. 
>
>Does DNS always use the unprivileged ports to send queries ?

It uses an unprivileged local port, unless you override this with a port
specification in the query-source option.

>Does DNS always receive answers and quesies on port 53 ?

It receives queries on port 53, it receives answers on the port that was
used when it sent out the query.

>Does the resolver use different ports than the DNS server ?

Yes, otherwise the system wouldn't know whether the answer should be sent
to the server or the resolver.

-- 
Barry Margolin, barry.margolin at level3.com
Level(3), Woburn, MA
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