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-   -   named -- using which port? (

icechong 01-30-2007 01:41 AM

named -- using which port?
Hi there,

I have just setting up a BIND server. when i activate the iptables allow ONLY TCP port 53(others all drop), the BIND server doesnt work well anymore.

other than port 53, which port or any other thing i should open up?


acid_kewpie 01-30-2007 01:58 AM

well DNS is 99% UDP... don't drop UDP/53.

icechong 01-30-2007 02:18 AM


Originally Posted by acid_kewpie
well DNS is 99% UDP... don't drop UDP/53.

how about TCP/53?

acid_kewpie 01-30-2007 02:32 AM

what about it... that'll be about 1% if that. TCP would only be a last resort for dns if the client even supports it. most dns servers won't listen for TCP at all.

icechong 01-30-2007 05:57 AM

Hi Acid_kewpie,

problem solved after i allow UDP/53. thanks very much for your support.


nx5000 01-30-2007 06:09 AM

AFAIK TCP will be used for reliable long queries or for zone transfers.
So if you block TCP/53 you might get intermitent failures in case udp packets are reorderd.
I wouldn't block TCP/53. rfc says that both transport methods can be used.

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