How to find IP address of a machine on network?

[Thomas Kaiser]

Chris G wrote:
> On Fri, Jan 16, 2009 at 08:08:26PM +0100, Nils Kassube wrote:
>> Chris G wrote:
>>> On Fri, Jan 16, 2009 at 11:34:11AM -0600, Wade Smart wrote:
>>>> Chris G wrote:
>>>>> How do I connect *to* the machine?  I need to know its IP address
>>>>> and, as there are a few devices which get their address by DHCP
>>>>> it's not at all obvious what the machine's address is.
>>>> System > Network Toos > Devices Tab, select eth0 and it will tell you
>>>> the ip of that machine.
>>> OK, thanks, not much use from the other end though is it!
>> Well, as long as you don't install any servers you can't connect. I 
>> suppose you want to install the package "openssh-server" and then you can 
>> use ssh to connect to the machine.
>>
> Quite right, so I have a machine that runs sshd and I want to connect
> to it and I know it's on the LAN but not its IP address.
> 

You can use nmap in a terminal to scan the network for open ports.

thomas at AMD64:~$ nmap 192.168.0.*

Starting Nmap 4.53 ( http://insecure.org ) at 2009-01-16 20:25 CET
Interesting ports on 192.168.0.1:
Not shown: 1711 filtered ports
PORT     STATE  SERVICE
23/tcp   closed telnet
80/tcp   open   http
8080/tcp closed http-proxy

Interesting ports on 192.168.0.2:
Not shown: 1709 closed ports
PORT    STATE SERVICE
22/tcp  open  ssh
139/tcp open  netbios-ssn
143/tcp open  imap
445/tcp open  microsoft-ds
993/tcp open  imaps

Interesting ports on 192.168.0.3:
Not shown: 1713 closed ports
PORT   STATE SERVICE
80/tcp open  http

Interesting ports on 192.168.0.4:
Not shown: 1709 closed ports
PORT      STATE SERVICE
21/tcp    open  ftp
22/tcp    open  ssh
23/tcp    open  telnet
80/tcp    open  http
31337/tcp open  Elite

All 1714 scanned ports on 192.168.0.11 are closed

All 1714 scanned ports on 192.168.0.13 are closed

Interesting ports on 192.168.0.16:
Not shown: 1711 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
80/tcp   open  http
5432/tcp open  postgres

Nmap done: 256 IP addresses (7 hosts up) scanned in 22.775 seconds


Regards, Thomas