Gain knowledge about Router, Router Internal Components and Router Booting process
What is Router
|
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 screen shot.
Router Ports:
LAN
Port: FastEthernet or Giga Ethernet
port
WAN
port: Serial port
Administration
Port: Console Port and AUX Port
Internal Parts of 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
Thanks,
NetworkSupportSolution
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