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Author Topic: BIND DNS server on TCP or UDP?  (Read 1571 times)

narke

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  • Posts: 9
BIND DNS server on TCP or UDP?
« on: April 26, 2009, 07:23:23 am »

Hello,

I have lauched BIND server on my computre to see how it works.
Then I scanned my host to see which ports were open and I saw that the 53  was open as TCP port.
I always read that DNS is working on UDP, so how can it handle UDP requests if it is accpeting only TCP packets?

Code: [Select]
bash-3.1# nmap localhost

Starting Nmap 4.60 ( http://nmap.org ) at 2009-04-26 16:02 GMT
Interesting ports on localhost (127.0.0.1):
Not shown: 1712 closed ports
PORT    STATE SERVICE
53/tcp  open  domain
631/tcp open  ipp
953/tcp open  rndc


Then I scanned with netstat and it shows that the port 53 is open as an UDP port.

Code: [Select]
bash-3.1# netstat -anu
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State     
udp        0      0 0.0.0.0:55829           0.0.0.0:*                         
udp        0      0 192.168.0.3:53          0.0.0.0:*                         
udp        0      0 127.0.0.1:53            0.0.0.0:*                         
udp        0      0 192.168.0.3:53          0.0.0.0:*                         
udp        0      0 127.0.0.1:53            0.0.0.0:*                         
udp        0      0 0.0.0.0:68              0.0.0.0:*                         
udp        0      0 0.0.0.0:50122           0.0.0.0:*                         
udp        0      0 0.0.0.0:631             0.0.0.0:*



So I am confused, how can it be TCP and UDP at the same time?
Which tool is wrong? Or it's me?

If I send an UDP packet does it will accept while running in TCP mode?

Thank's in advance

P.S:
I know that theorically UDP packets are for short requests and TCP packets are for zone tranfer.
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bigpaws

  • Vectorian
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  • Posts: 1869
Re: BIND DNS server on TCP or UDP?
« Reply #1 on: April 26, 2009, 07:46:17 pm »

A port can be open for TCP, UPD or both.

Bigpaws
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