Disable TCP/53

Jim Reid jim at rfc1035.com
Thu Feb 21 02:39:52 UTC 2002

>>>>> "Tan" == Tan Chun Han/ITNOC/PBB/PBBG <tanch at publicbank.com.my> writes:

    Tan> Hi, our firewall keeps detecting and rejecting TCP/53
    Tan> queries.  Does bind by default use TCP/53 and UDP/53? 

Yes. So does any name server that complies with the DNS protocol. Read
RC1035. Here's an excerpt:

	4.2. Transport

	The Internet supports name server access using TCP [RFC-793] on server
	port 53 (decimal) as well as datagram access using UDP [RFC-768] on UDP
	port 53 (decimal).

    Tan> Is there any way to disable TCP/53, thus enabling UDP/53?

No. [Not that disabling TCP/53 could somehow automagically enable
UDP/53 anyway.] Name servers are supposed to accept queries on port 53
from both TCP and UDP. That's what the DNS protocol says. Your
firewall is broken. Fix it.

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