named listening on UDP

[Peter Dambier]

Tom Schmitt wrote:
> Hi,
> 
> I have a (maybe) simple question, but google couldn't help me, so I try the list:
> 
> I downloaded Bind 9.3.4 and installed it on a Linuxserver (Debian-Etch). It's working fine. (Thank you for this piece of fine software!)
> 
> Because I'm a little bit paranoid I checked the ports where named is listening. netstat -tanp brought what I expectet: Port 53 on the external interface and port 53 and port 953 (for rndc) on the localhost-interface.
> 
> But netstat -uanp surprised me a little bit. Besides the expected ports 53 on the localhost and the external host, named is also listening on UDP-port 33186 on the external port. What is that for? I know of no reason to open this port. (also, named is listening on udp6-port 33187)
> 
> Can anyone tell me what the purpose of this open port is?
> 
> Thanks,
> Tom.

Sometimes named queries other nameservers e.g. the root-servers. Like any other program
named uses a random port to query this other nameserver on port 53.

Very likely, next time you start it, named will use a different port.

Kind regards
Peter and Karin


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Peter and Karin Dambier
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