Eddie On Everything » networking http://www.eddieoneverything.com Tips & tricks on things that interest me Wed, 11 Jan 2012 08:29:23 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 How to Scan a Computer for Open Ports http://www.eddieoneverything.com/articles/how-to-scan-a-computer-for-open-ports.php http://www.eddieoneverything.com/articles/how-to-scan-a-computer-for-open-ports.php#comments Fri, 08 Apr 2011 21:27:13 +0000 eddie http://www.eddieoneverything.com/articles/how-to-scan-a-computer-for-open-ports.php There are a bunch of GUI utilities for conducting port scans, but I prefer to work from a command line shell. 

In the past, I’ve used a custom script for scanning a machine for open ports from the command line, but I recently needed to get a little more information from a scan than my meager little script provides.

I did some research and found this useful tidbit on a Ubuntu forums site.

If you have any flavor of Linux, you should be able to use nmap to produce a map of open ports on a remote machine.

The command:

nmap -sS -sV –O  <IP ADDRESS>

Where the flags mean:

-sS: TCP SYN (Half-open) scan

-sV: Probe open ports to determine service/version info

-O: Enable OS detection

And example of the output:

root@frolicanddetour:/home/eddie/bin# nmap -sS -sV -O localhost

Starting Nmap 5.00 ( http://nmap.org ) at 2011-04-08 16:40 CDT
Interesting ports on localhost (127.0.0.1):
Not shown: 991 closed ports
PORT     STATE SERVICE     VERSION
22/tcp   open  ssh         OpenSSH 5.3p1 Debian 3ubuntu4 (protocol 2.0)
25/tcp   open  smtp        Postfix smtpd
80/tcp   open  http        Apache httpd 2.2.14 ((Ubuntu))
139/tcp  open  netbios-ssn Samba smbd 3.X (workgroup: GINGERALE)
443/tcp  open  ssl/http    Apache httpd 2.2.14 ((Ubuntu))
445/tcp  open  netbios-ssn Samba smbd 3.X (workgroup: GINGERALE)
631/tcp  open  ipp         CUPS 1.4
3306/tcp open  mysql       MySQL 5.1.41-3ubuntu12.6
5901/tcp open  tcpwrapped

You will have to be logged in as root to run this scan.  I like to set up an alias on my standard user account that employs sudo, like so:

alias portscan="sudo nmap -sS -sV -O $1"

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]]> http://www.eddieoneverything.com/articles/how-to-scan-a-computer-for-open-ports.php/feed 0 How to use your Netgear (or Linksys, or D-Link) wireless router as a Hub http://www.eddieoneverything.com/internet/how-to-use-your-netgear-or-linksys-or-d-link-wireless-router-as-a-hub.php http://www.eddieoneverything.com/internet/how-to-use-your-netgear-or-linksys-or-d-link-wireless-router-as-a-hub.php#comments Tue, 10 Nov 2009 19:52:56 +0000 eddie http://www.eddieoneverything.com/internet/how-to-use-your-netgear-or-linksys-or-d-link-wireless-router-as-a-hub.php Ok, here’s the deal:

I have 2 wireless routers, a Cisco and a Netgear.

The house’s primary router, a DD-WRT-based Cisco, is in my first-floor office. Unfortunately, the signal isn’t strong enough to make it to the third floor of my house.

I wanted to run a wire to the third floor of my home & use the Netgear router as a hub (both wired and wireless) on the third floor, letting the DD-WRT router continue to handle the firewall, DHCP, etc., for the entire house.

The problem was – there’s no setting in the Netgear WRT-642g configuration page for “hub mode.”

Searching yielded little helpful information. A few nuggets led me to do a bit of experimentation, and I discovered a working solution.

The trick: Connect the second router (the one you want to use as a hub) to the first using one of the second’s LAN ports, not it’s WAN port. That is, don’t use the port you would use to connect this router to your cable modem. Instead, use one of the other ports, usually labeled 1-4.

Doing this allowed me to use my Netgear router as a hub, even though it’s not officially supported.

Happy surfing!

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