For a Cisco exam you need to be able to very quickly convert between Decimal, Binary and Hexadecimal and back again.

Being able to recreate the below tables will greatly help will this

If you find yourself in ROMMON mode having done something silly like wiping the flash or if there was a problem updating the IOS then the below steps will go though how to copy a replacement image from tftp to the routers flash.

What you will need

- A tftp server, I tend to use tftpd32
- A compatible IOS image in the base directory of your tftp server
- The router need to be pluged into your network
- You need to be connected to the router via a console cable

The Commands

Enter the below commands one by one

Overview of the OSI Model

For Host-to-Host communications to to take place a consistent model is required especially when the Host-to-Host communications is taking place between different vendors. The OSI model was created so different vendors would have a standard way to get data from application to the physical wire.

The OSI model consists of seven layers or steps that data should go though while getting from an application to the physical wire.