Router vs. Switch vs. Bridges

Bridges and switches basicly perform the same function. Think of a switch as a bridge with much more ports.

A layer 3 switch perform the routing function (layer 3) in hardware, where a router would use CPU cycles and an operating system of some sort. The term "route one, switch many" apply with layer 3 switches. Only the first packet of a stream is passed to a router module or external router. The switch learn the destination address from the router and adds an entry to a table in memory. All packets of the same stream after that is switched between the input and output ports of the switch, completely bypassing the router.

Have a look at this link...
http://computer.howstuffworks.com/lan-switch.htm

Check here ... you can know the difference

http://www.practicallynetworked.com/networking/bridge_types.htm

Sunray

In my opinion a bridge and switch have a major difference beyong the number of ports.

A bridge isolates traffic on a network segment.

A,B,C are ports on a bridge.  A1,A2,B1,B2,C1,C2 are workstations plugged into the network.

A1,A2===(A)Bridge(B)====B1,B2
                     (C)                
                       |
                       |
                    C1,C2

If A1 is sending a packet to A2 then the bridge will ignore that packet and not forward it because it knows that A1 & A2 are on the same segment.

If A1 is sending to B1 then the bridge will broadcast the packets to all other ports (B & C in this example).

In other words...if I'm  a bridge I will either ignore a packet or forward it to all ports.

A Switch will complete a circuit from sender to reciever instead of broadcasting on all ports when traffic crosses a segment.

A1,A2===(A)Switch(B)====B1,B2
                     (C)                
                       |
                       |
                    C1,C2

As with the bridge if A1 is sending a packet to A2 then the Switch will ignore that packet and not forward it because it knows that A1 & A2 are on the same segment.

If A1 is sending to B1 then the Switch will forward the packer to port (B) only.

Fundamentally the Bridge is only concerned with the source while the Swtches is concerned about the Source and Destination.

Hi codenamecharlie,

NicBrey is right about the difference between switches and bridges and the link he send in was good. Praflik doesn't the point really.

Both a bridge and a switch are working by the same principle and work with the following states:

- learning : the device is ready to accept packets
- flooding : the device broadcasts the packets because he doesn't know to which port the host is attached
- forwarding : the device knows which port
- filtering : just sending to traffic to right ports and if the hosts are on the same port the traffic will not go through the switch
- aging : delete old addresses from the MAC-table.

So IMHO a switch and a bridge have the same function except a switch has more ports.

Cheers

I thought the point was "What is the difference between switches and bridges?"

You say there is none I say there is, otherwise why not just call it a 12 Port Bridge.

Bridges don't forward they flood.  I think that is a significant differance.

The only time they would work the same is if you had a two port switch and were comparing it to a two port bridge.

One last thing.

Bridges are often used to connect unlike topologies (Ethernet-to-Token Ring) (Ethernet-Serial/T1).

Ethernet Switches only connect Ethernet Segements togther.