Connecting two networks LAN/WAN, why do we need a Router?Can we solve it with a bridge

some not so pretty graphics to the above:



Computer room
internet -------------- <public ip  24.22.40.1 | router | private ip 192.168.115.1> ---------------<192.168.15.2 my computer>


Living room
<192.168.15.3 wirless bridge connected to above network's router>--------------------<192.168.15.4 my xbox360)

Basic use of a home router is to enable mutiple computers share one WAN ip, also a good measure of security in being behind a router.

:-) A slight disagreement, NAT should never be considered for security. It is one of the mechanisms but definitely not designed for security in mind.

Cheers,
Rajesh

Bridges were intended to be used with very old WAN networks.  Routers replaced them.  If you connect two layer 2 networks over a high latency bridge, your broadcast traffic flows across the high latency WAN connection to the other side - this either causes needless traffic across your WAN link, or it can needlessly create considerable lag in the performance of your network based applications.

Rotuers block broadcasts - tightening the "diameter" of your network.

Bah. put two windows xp computers on the network with no service packs, one in a dmz zone with a public ip and one behind a nat...  Let me know which one goes down first... o.O

Not to mention most routers come packaged with some kind of minimal firewalls.

It's not NAT which protects the devices - it's the device not forwarding ports unless explictly configured to do so which protects the devices.  So, it's sort of like a firewall - albeit not a stateful one.