Query source port 53

[Nico Kadel-Garcia]

Barry Margolin wrote:

> In article <bmeic1$esj$1 at sf1.isc.org>, Bragi Baldursson <bb at simi.is> wrote:
> 
>>I have been looking over the RFCs and the threads about the issue of using
>>source port 53 for querying and it seems to me
>>that the standard is to use port 53 as the query source port.
> 
> 
> This was the behavior of BIND 4, but AFAIK it's not specified in any
> standard.  And BIND 8 changed the default behavior -- it now selects an
> ephemeral source port.

It's mentioned in the default named.conf files for a lot of 
distributions. It is often still useful when configuring firewalls to 
allow things like zone transfers to secondary name servers outside your 
local network.