DNS Server on UDP and TCP
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Article ID: 18356
Last updated: 27 Jan, 2009
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Views: 357
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Posted: 22 Jan, 2009
by: Tech Pubs S.
Updated: 27 Jan, 2009
by: Tech Pubs S.
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DNS Server on UDP and TCP |
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| This script is Copyright (C) 2005-2009 Tenable Network Security, Inc. |
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| Family | DNS |
| Plugin ID | 18356 |
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| CVE ID |
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| Description: |
Synopsis :
The remote DNS server is not RFC1035 compliant.
Description :
A DNS server is running on this port but it only answers to UDP
requests. This means that TCP requests are blocked by a firewall.
This configuration is not RFC-compliant. Contrary to common belief,
TCP transport is not restricted to zone transfers (AXFR) :
- answers bigger than 512 bytes are always transmitted
over TCP.
- for all other requests, UDP is only preferred for
performance reasons. i.e. RFC1035 (STD0013) does not
forbid a DNS client from issuing its queries directly
over TCP.
See also :
http://www.faqs.org/rfcs/rfc1035.html
Solution :
If you are sure that the DNS server will never return answers bigger
than 512 bytes and that the client software prefers UDP (which is
nearly certain), you may ignore this message.
Risk factor :
None |
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