Router Components


Router Components 

Internal configuration components 



•      Processor- 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 which contain ‘Configuration Register’. The contents in the NVRAM remain even after the router is shutdown or rebooted.

•      Flash-  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.

•      Interfaces- They are physical connectors that connect the router to the network for packet entry and exit.
•      Power supply
       
     External configuration components 

  1. Interfaces- makes physical connections to the outside world. 
    • Ethernet and fast Ethernet
    • Asynchronous & synchronous serial
    • Token Ring
    • FDDI
    • ATM
    • Console and Auxiliary port 
1.RAM (Random Access Memory)

  • It is read and write memory.
  • It contains software and data structure.
  • It is principal software running the Cisco IOS image and Running-Configuration.
  • Some Routers (e.g.2500 series) run IOS from Flash and not RAM. 
2.NVRAM (Nonvolatile RAM)

  • Stores initial or startup configuration file.
  • It is not erased when the router/switch is reloaded.
  • Uses a battery to maintain the data when power is removed from the router. 
3.Flash Memory

  • Stores fully functional IOS image.
  • Not erased when the router is reloaded.
  • It is an EEPROM created by Intel.
  • Can be used to store configuration files on Cisco 7500 series platforms.
  • Some routers (e.g.2500 series) run the IOS image directly from flash and not from RAM. 
4.ROM (Read Only Memory)

  • Contains micro codes to start and maintain the router
  • Stores bootable IOS image
  • Contains the code that is used to boot the router until the router knows where to get the full IOS image. 
5.Configuration Register 

  • It’s a 16-bit  software register, written into NVRAM.
  • Used to control how the router boots up.
  • Value can be seen with the show version command and typically is 0X2102,which tells the router to load the IOS from flash memory. 
6.Interfaces

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