[105160] in North American Network Operators' Group
DNS problems to RoadRunner - tcp vs udp
daemon@ATHENA.MIT.EDU (Mark Price)
Fri Jun 13 14:11:46 2008
Date: Fri, 13 Jun 2008 14:11:11 -0400
From: "Mark Price" <mprice@tqhosting.com>
To: nanog@merit.edu
Errors-To: nanog-bounces@nanog.org
I have seen intermittent problems on some client windows servers
sending to rr.com recently.
For example, the MX hosts for triad.rr.com are:
# dig -t mx triad.rr.com
;; QUESTION SECTION:
;triad.rr.com. IN MX
;; ANSWER SECTION:
triad.rr.com. 1609 IN MX 10 hrndva-smtpin01.mail.rr.com.
triad.rr.com. 1609 IN MX 20 hrndva-smtpin02.mail.rr.com.
The authoritative nameservers for mail.rr.com:
# dig -t ns mail.rr.com
;; QUESTION SECTION:
;mail.rr.com. IN NS
;; ANSWER SECTION:
mail.rr.com. 14204 IN NS cdptpa-admin02.mail.rr.com.
mail.rr.com. 14204 IN NS hrndva-admin01.mail.rr.com.
mail.rr.com. 14204 IN NS hrndva-admin02.mail.rr.com.
mail.rr.com. 14204 IN NS cdptpa-admin01.mail.rr.com.
All 4 of those queries will answer a UDP DNS query for host record
hrndva-smtpin01.mail.rr.com.
However, the hrndva-admin01.mail.rr.com and hrndva-admin02.mail.rr.com
servers do not respond to TCP queries at all. Example:
# dig hrndva-smtpin01.mail.rr.com @hrndva-admin01.mail.rr.com +tcp
; <<>> DiG 9.3.3rc2 <<>> hrndva-smtpin01.mail.rr.com
@hrndva-admin01.mail.rr.com +tcp
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached
>From what I have read, public DNS servers should support both UDP and
TCP queries. TCP queries are often used when a UDP query fails, or if
the answer is over a certain length.
Any clues would be appreciated.
Mark
--
Mark Price
Tranquil Hosting
www.tqhosting.com
