Archive for the ‘Networking’ Category

When you type an incorrect command in the CISCO IOS terminal/Cisco Packet Tracer you may come across such an issue as show below:

Sample Translating domain server (255.255.255.255) output

To resolve this, use command “no ip domain-lookup” as shown below:

Router>enable

Router#configure terminal

Router(config)#no ip domain-lookup

Router(config)#exit

Finally, if you need to save the changes permanently, you can use the “write” command as shown below:

Router#write

Hope this helps! Feel feel to leave a comment if you have any queries or want to reach out to me. You can also Follow/Subscribe to my blog to get future blog posts! Happy Networking! 🙂

[ Source: Cisco ]

Regards,
ΞXΤЯΞМΞ

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So, What is a router??

Well, a router is a specialized computer used for networking. The main function of a router is route packets.  A router is just like a typical PC, has a CPU and memory components. In Cisco routers, it has the Cisco IOS which provides the basic routing logic. The router also has a ROM just like normal PCs, which contains the basic software to be run when the router is booted.

Example of a router

Internal Components of a Cisco Router:

A router consists of the following major components:

  1. CPU
  2. ROM
  3. RAM
  4. NVRAM
  5. Flash Memory
  6. RXBOOT  Image
  7. Interfaces
  8. Buses
  9. Power Supply
  10. Configuration Register

CPU: The CPU executes the instructions of the operating system. They also perform functions such as system initialization, routing functions, and network interface control.

ROM: This maintains the instructions for POST (Power on Self Test) for diagnosis and also stores the bootstrap program and basic OS software.

RAM: It stores the routing tables and the configuration file while the router is powered on. The “running-config” is stored here. The contents of the RAM are lost when the router is restarted or powered down.

NVRAM: It stores the “startup-config” file. The contents in the NVRAM remain even after the router is shutdown or rebooted.

Flash Memory: This is the location where the “Cisco IOS image file” is stored which is the operating system of the router itself. The contents in the flash memory remain even after reboot or shutdown. This is a type of EEPROM.

RXBOOT Image: This is a cut-down version of the the IOS located in the router’s ROM.

Buses: Most routers consist of a system bus and a CPU bus. Buses provide physical means for the router to move bits among the different components of the router. Most routers contain a system bus and a CPU bus.  The system bus communicates between the CPU and the interfaces. For example, this bus transfers the packets to and from the interfaces. The CPU bus is used by the CPU for accessing router’s storage devices like NVRAM and flash memory.

Interfaces: They are physical connectors that connect the router to the network for packet entry and exit.

Power Supply: The power supplies can be internal or external to the router. Some routers have multiple power supplies for redundancy.

Configuration Register: The configuration register is what decides if the router is going to boot from the IOS image from the tftp server or the RXBOOT image.

ΞXΤЯ3МΞ

We can find the IP address of any host or website using the “ping” command.

If you are using Windows,  open up the command prompt by pressing Start, then press Run and then type:

cmd

and hit ENTER.

This will bring up the command prompt. In this window, type “ping” following by the “host” whose IP address you want to find. For example, if you want to find the IP address of http://www.google.com,in your command prompt window, type:

ping google.com

using ping to find IP address

The above picture shows a sample output of the ping command. Here you can see that the IP Address I got is the one I have marked inside the red box and this is the I.P. address of the website http://www.google.com.

 

ΞXΤЯ3МΞ

Hey everyone, I would like to show you some basic network programming stuff in python (v2 or higher). This is purely for coders who have some basic knowledge in python and want to begin network programming in Python.

So, open up your Python Interpreter or Python IDE and open a new window. I am gonna show you some basic stuff you can do like how to get your host name or I.P. address using python. Of course, there is a much shorter way to write this code. I have written this code for beginners to understand what is actually going on.

___________________________________________________________________________________

# Program to print your host name

import socket                 # This  imports the socket module for using its functions

hostname=socket.gethostname()                   # This will return your hostname

print "Your Host name is : " + name

raw_input("Enter any key to continue...")

#End of Code

Save it and run it. It will print your hostname. Simple rite?? Yeah! There is your first simple program.

___________________________________________________________________________________

Now, let’s write another simple program used to resolve a given hostname to its I.P. Address. This is done by using the function socketname.gethostbyname(hostame)

# Hostname Resolver

import socket

hostname=raw_input("Enter the hostname to resolve :")

ip=socket.gethostbyname(hostname)            # Return  corresponding IP address to variable ip

print "IP ADDRESS : " + ip                   # Prints the retrieved IP Address

raw_input("Enter any key to continue.. ")


# End of Code

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Happy Coding!

CheerS!!

ΞXΤRΞМΞ-X