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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
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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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LEARN ABOUT DEBIAN

ka-forwarder

KA-FORWARDER(8) 					       AFS Command Reference						   KA-FORWARDER(8)

NAME

       ka-forwarder - Forward AFS Authentication Server requests to another server

SYNOPSIS

       ka-forwarder [-p <port>] <server>[/<port>] [...]

DESCRIPTION

       ka-forwarder listens for requests for an AFS Authentication Server and forwards them to a remove fakeka server.	fakeka is a server that
       answers AFS Authentication Server protocol requests using a regular Kerberos KDC and is provided with some Kerberos 5 implementations.
       fakeka has to run on the same host as the Kerberos KDC, however, and AFS clients send all native AFS authentication requests to the AFS
       database servers.  If you don't want to run your Kerberos KDCs and your AFS database servers on the same host, run ka-forwarder on the AFS
       database servers and point it to fakeka running on the Kerberos KDCs.

       ka-forwarder takes one or more servers to which to forward the requests.  The default port on the remote server to which to forward the
       command is 7004, but a different port can be specified by following the server name with a slash ("/") and the port number.  If multiple
       servers are given, ka-forwarder will send queries to each server in turn in a round-robin fashion.

CAUTIONS

       Due to the way that ka-forwarder distinguishes from client requests and server responses, any messages from one of the servers to which ka-
       forwarder is forwarding will be considered a reply rather than a command and will not be forwarded.  This means that the servers running
       fakeka will not be able to use native AFS authentication requests and rely on ka-forwarder to send the requests to the right server.

       ka-forwarder does not background itself.  It should either be run in the background via the shell, or run via the Basic OverSeer Server
       (see bosserver(8)).

OPTIONS

       -p <port>
	   By default, ka-forwarder listens to the standard AFS Authentication Server port (7004).  To listen to a different port, specify it with
	   the -p option.

EXAMPLES

       Forward AFS Authentication Server requests to the fakeka servers on kdc1.example.com and kdc2.example.com:

	   % ka-forwarder kdc1.example.com kdc2.example.com &

       Note the "&" to tell the shell to run this command in the background.

PRIVILEGE REQUIRED

       ka-forwarder only has to listen to port 7004 and therefore does not require any special privileges unless a privileged port is specified
       with the -p option.

SEE ALSO

       bosserver(8), fakeka(8), kaserver(8)

COPYRIGHT

       Copyright 2006 Russ Allbery <rra@stanford.edu>

       This documentation is covered by the IBM Public License Version 1.0.  This man page was written by Russ Allbery for OpenAFS.

OpenAFS 							    2012-03-26							   KA-FORWARDER(8)