21-07-2012, 02:20 PM
Cisco Routers
Cisco Routers.ppt (Size: 586.5 KB / Downloads: 65)
Interfaces on a Router
1. Ethernet It is a LAN interface. Some of the models have an RJ45 port for 10baseT or 10/100. And some other have a 15 pin female connector AUI (Attachment Unit Interface).
2. Serial It is a 60 pin female WAN interface for leased line
3. BRI/PRI It is a RJ45 WAN interface for ISDN
4. Async It is a 37 pin female connector for dial ups.
5. Console It is a RJ45 Connector used to configure the Router for the first time.
6. Auxiliary RJ45 Connector for remote access administration.
Internal Components of a Router
Boot ROM : It stores the mini IOS (Internet work Operating System) image (RX Boot) with extremely limited capabilities and POST routines and core level OS for maintenance.
FLASH : It is an EPROM chip that holds most of the IOS Image. It maintains everything when router is turned off.
RAM : RAM holds running IOS configurations and provides caching. RAM is a volatile memory and looses its information when router is turned off. The configuration present in RAM is called Running configuration.
NVRAM : It is a re-write able memory area that holds router’s configuration file. NVRAM retains the information when ever router is rebooted. Once configuration is saved, it will be saved in NVRAM and this configuration is called Startup Configuration.
Configuration of a Router
Router for the first time is configured through the CONSOLE port.COM port of a PC is connected to the console port of router with a console cable by using a transceiver. Router is accessible by a tool. In windows, it is called HYPER TEMINAL. As soon as the router is powered on and accessed, the following things happen,
The “CDP”
It’s a Cisco's proprietary protocol called the Cisco Discovery Protocol, that gives you a summary of all the directly connected Cisco devices. CDP is a L2 protocol, that discovers neighbor regardless of which protocol suite they are running. When a cisco device boots up, the CDP is loaded by default, but can be disabled at interface level.
* The CDP is limited to the immediate neighbors only…
The summary includes Device Identifier(eg. Switch configured name or domain name), Port Identifier (eg. Ethernet 0 and serial 0.), Capabilities list (eg. The device can act as a sourcr route bridge as well as a router), Platform (eg. Cisco 2600).
Routing
Routing is of three types.
Static
Dynamic and
Default
When the destination is known, static and dynamic routing is done. For unknown destinations, default routing is employed.
In dynamic routing, the path is fixed by the protocol. The paths will be changing depending on the length of the path. Always the shortest path is preferred. Static routing is done by the users. These paths are stored in the routing table.