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The Penguin's Practical Network Troubleshooting Guide - page 3

Mapping Network Hosts and Services

  • December 15, 2008
  • By Carla Schroder

It is amazing how many different uses nmap has. Just when you think you know it inside out, out pop more interesting and useful features. This command scans a subnet to see what hosts are up:

# nmap -sP 192.168.1.*

Starting nmap 3.81 ( http://www.insecure.org/nmap/ ) at 2006-04-27 14:54 PDT
Host 192.168.1.0 seems to be a subnet broadcast address (returned 2 extra pings).
Host windbag.alrac.net (192.168.1.10) appears to be up.
Host uberpc.alrac.net (192.168.1.11) appears to be up.
MAC Address: 00:10:0A:54:61:DA (Unknown)
Host stinkpad.alrac.net (192.168.1.12) appears to be up.
MAC Address: 00:1A:E2:4A:8B:DD (Wistron)
Host 192.168.1.255 seems to be a subnet broadcast address (returned 2 extra pings).
Nmap finished: 256 IP addresses (3 hosts up) scanned in 7.005 seconds

 

Want to map your entire network and see what services are running?

# nmap -O 192.168.1.*

Starting nmap 3.81 ( http://www.insecure.org/nmap/ ) at 2006-04-27 22:06 PDT
Interesting ports on windbag.alrac.net (192.168.1.10):
(The 1658 ports scanned but not shown below are in state: closed)
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
139/tcp open netbios-ssn
445/tcp open microsoft-ds
631/tcp open ipp
Device type: general purpose
Running: Linux 2.4.X|2.5.X|2.6.X
OS details: Linux 2.5.25 - 2.6.3 or Gentoo 1.2 Linux 2.4.19 rc1-rc7)
Uptime 1.567 days (since Wed Apr 26 08:30:31 2006)
'output snipped'

Nmap finished: 256 IP addresses (3 hosts up) scanned in 8.341 seconds

 

There are a whole lot of open services here. The -O tells nmap to try to identity the operating systems.

 

Related Articles

Remote Testing
Running tests from outside your LAN, and from different geographical locations, is a great way to pinpoint trouble spots. A good way to do this is to have nice friends in other cities or other countries who give you shell accounts on their servers. Another way is to use Websites that are set up for remote network testing; see Resources for a list. You can do some low-budget remote testing without leaving your network administrator lair by using a dialup Internet account.

Resources

Article courtesy of Enterprise Networking Planet

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