I'm getting slow DNS response from ssh and other network related traffic with delay of 30-60+ seconds per connection. All of our servers are behind hardware based dedicated firewall. My RHEL v6.1 server system running on HP hardware. How do I fix this problem?
This is well known problem with RHEL 6 based systems and can be fixed by adding the following line to /etc/resolv.conf
Save and close the file. This should fix the problem as the resolver uses the same socket for the A and AAAA requests. Turning this option on changes this behavior so that if two requests from the same port are not handled correctly it will close the socket and open a new one before sending the second request.
-  This solution is documented RHN KB ID # 58626 (Red hat subscription required)