If you happen to move to vista or windows 7 like me, you have realized that hyper-terminal is no longer available. Although you could still make hyper-terminal work in windows 7 by copying the executable along with a dll file, I find that is much easier and convenient to use Putty. Putty offers many ways to connect to remote device like SSH, Telnet, and Serial. Here I describe how simple it is to connect to a device like a CISCO Router or switch using Putty.

1- First start by downloading putty from here

2- Second find on the device manager what is your serial connection: COM1 or 2 etc.

Read the rest of this entry »

I decided to make a guide about TCP/IP configuration in Linux, and you may ask: well, what Linux distribution in specific? I know!, there are hundreds of Linux distribution, but for this guide, I’m only going to cover the two most used Linux distribution: Ubuntu and Fedora. Ubuntu is a Debian derivative, so the Ubuntu portion of TCP/IP configuration applies to any distro based on Debian. And the same goes for Fedora, which is based on RedHat Linux.

First, you want to find out what interfaces you have, and what ip address, “if any,” was assigned to your computer. For this use the “ifconfig” command:

ifconfig  #will list all enabled interfaces

if you are looking for a specific interface:

ifconfig eth0 #will only display the configuration for eth0 interface

If you get no interfaces other than the loopback address, it is time to do some troubleshooting and find out whether your network card was detected by Linux or not.

sudo lspci | grep -i ethernet #displaying all your ethernet cards

if you’re troubleshooting a wireless card just change “ethernet” for “wireless.”
other useful command when troubleshooting network card and drivers is “lsmod” Read the rest of this entry »

Understanding subnetwork mask can be confusing if you’re not used to them. You may find “ipcalc” (from ipcalc package) useful to calculate a computer network’s mask.

First start by installing “ipcalc” from the repositories, depending on your distro:

sudo apt-get install ipcalc #for debian distros like ubuntu
yum install ipcalc #for fedora

then find the ip address for which you want to calculate the network for, and enter it along with “ipcalc” command

[root@Fedora11-vbox ~]# ipcalc -bmn 192.168.10.122/22
NETMASK=255.255.252.0
BROADCAST=192.168.11.255
NETWORK=192.168.8.0

So in this scenario, the subnetmask is (255.255.252.0), the broadcast address (192.168.11.255), which means that the last usable ip address for that network is (192.168.11.254), and last the network address (192.168.8.0); therefore, the first ip address for that range will be (192.168.8.1).

VNC is considered to be an insecure protocol. The password is sent using fairly weak encryption, and the rest of the session is not encrypted at all. For that reason, when using VNC over an untrusted network or internet, I recommend you tunnel it over SSH.

To forward VNC port 5900 on localhost to remote host port 5900

ssh -L 5900:localhost:5900 vncserver

If your ssh server is listening on other port like: 222

ssh -L 5900:localhost:5900 vncserver -p 222

The same procedure can be done on a window$ machine using putty Read the rest of this entry »

TCP/IP:The TCP/IP protocol is a stack of protocols. consisting of several different protocols, on layes 3 and 4 of the OSI model, including TCP, IP, ARP, DHCP, ICMP, and others.
TCP – Transport Control Protocol: is a layer 4 protocol that is commonly used because it provides an efficient method of reliable bi-directional communication, where computers can transmit and receive data simultaneously.
IP - Internet Protocol: is a layer 3 protocol that provide the addressing system that allows communication on the network, IP is a connectionless protocol which means that it needs of TCP to ensure the reliability of transmitted data.
The TCP 3 way handshake:before you can transfer data from another computer, the sender and the receiver need to complete the TCP 3 way handshake. The handshake is a 3 step process where the client computer establishes a connection with the server computer. All of this is possible through the different types of TCP packets and flags: SYN, SYN/ACK, ACK.
You can see the full 3 way handshake in the following figure. Read the rest of this entry »