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Forcing named 9 to use a fixed ephemeral port range

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Operating Systems AIX Forcing named 9 to use a fixed ephemeral port range
# 1  
Old 02-02-2018
Forcing named 9 to use a fixed ephemeral port range
I'll start with I'm not an AIX expert, I inherited a lot of AIX servers to maintain.

My problem is on AIX 7.1 TL4 SP4 environments. I'm running named as a DNS forwarder only to internal DNS servers.

These AIX servers have a customized UDP ephemeral port range to avoid conflicting with the primary application running on them that defaults to a portion of the typical ephemeral range.

Since configuring named, I've seen that named is ignoring the OS configured ephemeral range.

The OS restricted UDP range is: 32768 to 49999.
I've seen requests from named using source ports above 49999.

After googling, the only article I can find that references named/bind and ephemeral ports is a page from ISC related to BIND 9. There's a setting "use-v4-udp-ports { range 1024 65535; };" that forces named to use a fixed UDP range for source ports. But the IBM documentation on named doesn't cover this option.
I tried putting the setting onto named.conf on a test system but now named won't start and no errors are logged.
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net::dns::resolver::recurse

Net::DNS::Resolver::Recurse(3)				User Contributed Perl Documentation			    Net::DNS::Resolver::Recurse(3)

NAME

       Net::DNS::Resolver::Recurse - Perform recursive dns lookups

SYNOPSIS

	 use Net::DNS::Resolver::Recurse;
	 my $res = Net::DNS::Resolver::Recurse->new;

DESCRIPTION

       This module is a sub class of Net::DNS::Resolver. So the methods for Net::DNS::Resolver still work for this module as well.  There are just
       a couple methods added:

   hints
       Initialize the hint servers.  Recursive queries need a starting name server to work off of. This method takes a list of IP addresses to use
       as the starting servers.  These name servers should be authoritative for the root (.) zone.

	 $res->hints(@ips);

       If no hints are passed, the default nameserver is asked for the hints.  Normally these IPs can be obtained from the following location:

	 ftp://ftp.internic.net/domain/named.root

   recursion_callback
       This method is takes a code reference, which is then invoked each time a packet is received during the recursive lookup.  For example to
       emulate dig's "+trace" function:

	$res->recursion_callback(sub {
	    my $packet = shift;

	    $_->print for $packet->additional;

	    printf(";; Received %d bytes from %s

",
		$packet->answersize,
		$packet->answerfrom
	    );
	});

   query_dorecursion
       This method is much like the normal query() method except it disables the recurse flag in the packet and explicitly performs the recursion.

	 $packet = $res->query_dorecursion( "www.netscape.com.", "A");

IPv6 transport
       If the appropriate IPv6 libraries are installed the recursive resolver will randomly choose between IPv6 and IPv4 addresses of the
       nameservers it encounters during recursion.

       If you want to force IPv4 transport use the force_v4() method. Also see the IPv6 transport notes in the Net::DNS::Resolver documentation.

AUTHOR

       Rob Brown, bbb@cpan.org

SEE ALSO

       Net::DNS::Resolver,

COPYRIGHT

       Copyright (c) 2002, Rob Brown.  All rights reserved.  Portions Copyright (c) 2005, Olaf M Kolkman.

       This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

       $Id: Recurse.pm 932 2011-10-26 12:40:48Z willem $

perl v5.16.2							    2012-01-27					    Net::DNS::Resolver::Recurse(3)