The DNS server will send requests to other DNS servers on a port other than its default port (TCP port 53). This is done ...

The DNS server will send requests to other DNS servers on a port other than  its default port (TCP port 53).  This is done to accommodate configuration  changes you have made at the DNS server and prevent it from failing to  receive DNS queries it makes to other servers.  You might want to change this  behavior.  For more information, see "DNS server log reference" in the online Help.  
  
This DNS server is multi-homed (running on multiple IP addresses), but has been  configured NOT to run on ALL IP addresses available on the machine.  Under these  conditions it is impossible to guarantee that a DNS query to a remote DNS server  will be sent with one the IP addresses the DNS server is using, and hence whether  the response to that IP address will be received on the DNS port.  To avoid this  problem, sends to other DNS servers will be done on a arbitrary (non-DNS) port and  the response will be received regardless of the IP address used.  
  
If you wish to use the DNS port for sends to other DNS servers, then you must change  your configuration to either:  
	1) use all IP addresses on the machine for DNS (i.e. eliminate the listen address list)  
	or  
	2) limit the DNS server to use a single IP address.