Open dns port issue on Linux

Dear experts,
I'm haveing a issue to open a dns port on Fedaro Core 4.
I have tried using /usr/sbin/lokkit and put 53:tcp in Other ports. And then click ok to exit.
I used namp hostname and cannot see port 53 was opened and also cannot telnet hostname 53.
I also tried restart service iptables.

Please let me know how to fix the issue.

Thanks,
Yan
luyanAsked:
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slyongCommented:
DNS is using UDP if I am not wrong.  Try opening 53:UDP instead of TCP.
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luyanAuthor Commented:
sorry, one of opened port on my another dns machine is 53:tcp.

Thanks
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slyongCommented:
Hi luyan,

check out this http://www.cyberciti.biz/tips/linux-iptables-12-how-to-block-or-open-dnsbind-service-port-53.html.  DNS queries are handled via UDP and only larger request (e.g. zone transfer) is handle via TCP.  The example also shows how to open up port for incoming DNS request or outgoing DNS request.
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