Zone Transfers, Which port please....

[Barry Margolin]

In article <890B12B8398AD211BC6100805FA784A205383722 at es04snlnt.sandia.gov>,
Cinense, Mark <macinen at sandia.gov> wrote:
>	Does anyone know of which port BIND uses for zone transfers?  Is it
>port 53?  We are planning on closing port 53 and restricting only our
>namservers to have access through port 53.  All answers are greatly
>appreciated.

Yes, port 53 is used for zone transfers.  It's also used for ordinary
queries.  Normally UDP is used, but TCP will be used if the response is
bigger than 500 bytes.  There's also no prohibition against using TCP for
other queries (the standard says clients SHOULD try UDP first, but it
doesn't say MUST).

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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