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The Penguin's Practical Network Troubleshooting Guide - page 4

Start with Cable Testing

  • June 6, 2006
  • 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.

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