A Router is Network Layer or layer3 based device this device is used to route packets from one network to the other network or we can say that router is used to route packets from local network to wide area network. Router always uses the best path to route packets on networks.

As we know that our Desktop computers and Servers have Operating System (O.S.).Example: Windows XP, Windows 7, Windows Server 2003,2008,2012, Linux, Centos, Ubuntu and more.Cisco devices also have an OS which is called the IOS (Internetwork Operating System).

The IOS is the command line (CLI) interface which through we can done all the configurations for network devices.

The IOS is stored into the Flash memory.

The Flash memory is a non-volatile memory. Example: In case, the device lost the power the configuration remain saved into the memory and not lost. The configuration can be changed or edit when required.

Here we are showing the router panel from backside that mostly common for most of the models. Look the below screenshot.

Router’s Ports:

Learn about Router, components and Process

LAN Port: FastEthernet or Giga Ethernet portWAN port: Serial portAdministration Port: Console Port and AUX Port

Other Internal parts of a Router:

Read Only Memory ( ROM ):   This is a chip on the motherboard which is coded with a bootstrap program which tells how the IOS should be loaded.

It starts and maintains the router. It contains the POST, mini-IOS and the Bootstrap program.

Random Access Memory ( RAM ) :  This holds the running or temporary config, the ARP cache, the routing tables and the software that help router to run.

It is also known as the running config. During boot, the IOS is loaded from the flash to the RAM

Flash Memory:  the place where the IOS is actually stored. It DOES NOT erase when we reload the router.Non Volatile RAM ( NVRAM ):  This holds the configuration for router and switch. The IOS is not stored here, but the configuration register is stored here. NVRAM will not erase if a switch or router is reloaded.

Power On Self-Test (POST): This does automatically check the basic functionality of hardware for router and determines the interfaces present on it.

Mini-IOS: This is the boot loader or RXBOOT, provided by Cisco. This is a small IOS used to bring up and interface and help load the Cisco IOS into flash memory. It is stored in the ROM.Configuration Register File: This controls how the router should boot up. Usually used while doing password recovery on router. The show version output shows this file. The

default value set is 0×2102, which informs to load IOS from flash and to load the configuration to NVRAM

Router Booting Process:

Post to identify the hardware Components. Bootstrap Program is looked up from the ROM IOS is loaded from the Flash memory Flash memory contacting to NVRAM NVRAM configuration is copied into RAM