DIFFERENCE BETWEEN BRIDGING/SWITCHING AND ROUTING....

 There is a fundamental question: “how is bridging different from routing?”. It’s impossible to give a concise answer .
ROUTING-: Routing or routeing is the process of selecting paths in a network along which to send network traffic.
BRIDGING-: Bridging is a forwarding technique used in packet-switched computer networks. Unlike routing, bridging makes no assumptions about where in a network a particular address is located. Instead, it depends on flooding and examination of source addresses in received packet headers to locate unknown devices. Once a device has been located, its location is recorded in a table where the MAC address is stored so as to preclude the need for further broadcasting. The utility of bridging is limited by its dependence on flooding, and is thus only used in local area networks.


                             NOW THE DIFFERENCES BETWEEN THESE TWO--

Design scope. IP was designed to support global packet switching network infrastructure. Ethernet bridging was designed to emulate a single shared cable. Various design decisions made in IP or Ethernet bridging were always skewed by these perspectives: scalability versus transparency.

Forwarding. IP routers forward

UNEQUAL COST LOAD BALANCING WITH STATIC ROUTES

Unequal load-sharing with static routes is almost impossible as there is no configuration command to assign non-default traffic share count to a static route. For example, if you configure two default routes, one pointing to a low-speed interface and another one pointing to a high-speed interface, there is no mechanism to force majority of the traffic onto the high-speed link (IOS ignores interface bandwidth when calculating load sharing ratios).

You can, howerer, use a workaround: if you configure multiple routes for the same prefix pointing to the same interface, that interface will attract proportionally more outbound traffic.

For example, let's assume you have two point-to-point serial subinterfaces, one three times as fast as the other:

interface Serial0/0/0.100 point-to-point
 bandwidth 1000
 ip address 172.16.1.1 255.255.255.252
!
interface Serial0/0/0.200 point-to-point
 ip address 172.16.1.5 255.255.255.252
 bandwidth 3000

To shift more traffic onto Serial0/0/0.200,

Router Boot process

Router uses a systematic way to boot. It goes through the following process during bootup.--

POST-(Power On Self Test)-- Testing the H/W Components of Router
Load  Bootstrap Loader from ROM to RAM and Execute it.Then Bootstrap loader locate the IOS image and copy it into RAM.
Locating the Configuration file if any in NVRAM .
Loading the Configuration file in RAM. if their is no file than the Router will prompt the user to enter Setup mode.

Router Component

A Router is a computer. it has many of same hardware & software components.like-

  RAM-store running configuration,IOS during bootup, ARP & ip routing Table.It is Volatile memory.
  NVRAM- Nonvolatile, store startup config

  ROM- Permanent storage,that used for Bootstrap program, Scaled down version of IOS
  Flash Memory- permanent storage, stores Cisco IOS

  CPU- Executes IOS Instructions
  Operating System- Cisco IOS
  Interfaces- to connect devices