cache dns server use tcp to query other dns server
Alex Tang
alextang at cms.hkcable.com
Tue Jan 10 06:22:16 UTC 2006
fyi
at the frist time, it should query the mx record of a domain gsncashgames-news.com
-----Original Message-----
From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org]On Behalf Of Alex Tang
Sent: Friday, January 06, 2006 4:53 PM
To: Barry Margolin; comp-protocols-dns-bind at isc.org
Subject: RE: cache dns server use tcp to query other dns server
Importance: High
I use the snoop on my cache dns server and find out follow things
my cache dns server query other dns server ( ns3.texasdns.com) it return 27 answer
IP: Source address = 69.56.15.2, ns3.texasdns.com
IP: Destination address = x.x.x.x, (my cache dns server)
IP: No options
IP:
UDP: ----- UDP Header -----
UDP:
UDP: Source port = 53
UDP: Destination port = 50538
UDP: Length = 47
UDP: Checksum = 2852
UDP:
DNS: ----- DNS Header -----
DNS:
DNS: Response ID = 61365
DNS: AA (Authoritative Answer) TC (TrunCation)
DNS: Response Code: 0 (OK)
DNS: Reply to 1 question(s)
DNS: Domain Name: gsncashgames-news.com.
DNS: Class: 1 (Internet)
DNS: Type: 15 (Mail Exchange)
DNS:
DNS: 27 answer(s)
ETHER: ----- Ether Header -----
ETHER:
ETHER: Packet 3 arrived at 15:37:49.98
after that my cache dns server try to use tcp but have some problem
IP: ----- IP Header -----
IP:
IP: Version = 4
IP: Header length = 20 bytes
IP: Type of service = 0x00
IP: xxx. .... = 0 (precedence)
IP: ...0 .... = normal delay
IP: .... 0... = normal throughput
IP: .... .0.. = normal reliability
IP: Total length = 41 bytes
IP: Identification = 58703
IP: Flags = 0x4
IP: .1.. .... = do not fragment
IP: ..0. .... = last fragment
IP: Fragment offset = 0 bytes
IP: Time to live = 64 seconds/hops
IP: Protocol = 6 (TCP)
IP: Header checksum = 33c1
IP: Source address = x.x.x.x, my cache dns server
IP: Destination address = 64.202.167.159, ip-64-202-167-159.secureserver.net
IP: No options
IP:
TCP: ----- TCP Header -----
TCP:
TCP: Source port = 50931
TCP: Destination port = 53 (DNS)
TCP: Sequence number = 858230409
TCP: Acknowledgement number = 3084354847
TCP: Data offset = 20 bytes
TCP: Flags = 0x10
TCP: ..0. .... = No urgent pointer
TCP: ...1 .... = Acknowledgement
TCP: .... 0... = No push
TCP: .... .0.. = No reset
TCP: .... ..0. = No Syn
TCP: .... ...0 = No Fin
TCP: Window = 25192
TCP: Checksum = 0x21da
TCP: Urgent pointer = 0
TCP: No options
TCP:
DNS: ----- DNS: -----
DNS:
DNS: ""
DNS:
it only try to query DNS: "". Why ? Is it normal . fyi my firewall only allow our clients ip to query the cache dns server high port. and only established tcp is allowed to come into the segment.
Do i miss some configuration ?
-----Original Message-----
From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org]On Behalf Of Barry Margolin
Sent: Friday, January 06, 2006 2:24 PM
To: comp-protocols-dns-bind at isc.org
Subject: Re: cache dns server use tcp to query other dns server
In article <dpkon2$ms1$1 at sf1.isc.org>,
"Alex Tang" <alextang at cms.hkcable.com> wrote:
> or if my cache dns server cannot get answer from other dns server by udp ,
> will my cache dns server change to use tcp to query the no answered other dns
> server ?
No, BIND doesn't do that. It only uses TCP for ordinary queries when
the UDP attempt returns a truncated response.
--
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***
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