dns server.
 

i have a problem finding dns server in my university network.
i have connected to internet via proxy server in the university.
can anyone know the port number of dns server so that i can locate a dns server IP address by using nmap.

or any command to lookup a dns server.

port 53 (usually UDP and TCP both active)

Try with nslookup or dig.

--
Prasanta

As prasanta said, use nslookup, like so:
nslookup
#=> gives you an nslookup prompt
#it should already tell you the default DNS server you're using (so if you're connected to the univ network,
#then you already have your answer...
#otherwise:
<univ_domain>
#This should respond with some NS (NameServer) records for the domain <univ_domain>.

#Similarly, you can also check out the mail server, etc:
set type=MX
<univ_domain>
#=> mailserver is an MX record in the DNS database.

I always find it easiest to get the DNS server settings off a working system on the [foreign] network. Go to a box that is working on the network and either:

Linux: cat /etc/resolv.conf
Windows 2k/XP: from a command prompt type ipconfig /all and note the DNS servers
Windows 9x/ME: run winipcfg