Cisco Router

Router

⦁ A router is a networking device which makes communication possible between two or more different network present in same or different geographical locations.

⦁ It works on layer 3 of the OSI model so it is known as L3 device.
⦁ It also selects the best path at minimum cost from the routing table and    forward the packet which is the best one for communication.

Vendors of Router:-

⦁ Cisco
⦁ Juniper
⦁ Nortel
⦁ Multicom
⦁ D-Link
⦁ Linksys
⦁ 3com

Cisco Three-Layered Hierarchical Model:-

A. Access Layer :- Router which is used by the small organization and are also known as the Desktop or Company layer routers. Router series: 800,1000,1600,1700,2500 etc.

B. Distribution Layer:- Router which is used by the ISPs and are also known as an ISP layer Router. Router series: 2600,3200,3600 etc.

C. Core layer:- Router which is used by the Global ISPs and are also known as Backbone Router. Router Series: 6400,7200,7400,10000 etc.

Classification of Router:-

Fixed Router:-
It’s also known as Non-Upgradeable Router Because in this router we can’t add or remove the Ethernet or serial interface according to own requirement.
It does not have any slot for adding or removing the interface.

Modular Router:-
It’s also known as Upgradeable Router Because in this router we can add or remove the Ethernet or serial interface according as per the requirement.
It has number of slot for adding or removing the interface.

Bringing up a Router:-

⦁ First switch-on and it goes for Power-on self Test (POST).
⦁ It load Cisco IOS from flash memory if it present on it.
⦁ The IOS then proceeds to load and looks for a valid configuration which is stored by default in non-volatile RAM, or NVRAM.
⦁ IOS is decompressed into RAM
⦁ After IOS is decompressed into RAM, the IOS then loaded and start running the router.

Fig: Bringing Up a Router

Following Message Appear when we first boot or reload a router:

Fig: Cisco Router IOS