bridge vs router

I always seem to get the two devices confuse.

What's the difference between a bridge and a router?

Both devices seem to seperate the traffic from the two different networks.

When I take the tech exam one question ask:

What of the following can be used to reduce broadcast on the network by separating broadcast domains?

Only Routers and VLANs are the correct answers.

Why isn't the bridge consider to be the correct answer as well?

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Comments

keatron

Well, the difference in these two can be confusing. Some of the confusion comes from people in our industry sometimes incorrectly using the two terms synonomously. A good understanding of the OSI model is crucial for really understanding the main differences. I say that because bridges are layer 2 devices, and routers are layer 3 devices. Bridges don't know anything about protocols, but just forward data depending on the destination address in the data packet. This address is not the IP address, but the MAC (Media Access Control) address that is unique to each network adapter card. The bridge is basically just to connect two local-area networks (LANs), or two segments of the same LAN that use the same protocol. Routers forward data depending on the Network address, not the Hardware (MAC) address. For TCP/IP networks, this means the IP address of the network interface. For a device to do something like seperate broadcast domains etc etc etc, it has to be able to work on or with layer 3. So in short, a bridge can't route an ip address because it can't read them! It reads the MAC address and the MAC address only.

ASUSTeK

Since we're on the topic. Can anyone please explain to me what is or what is the purpose of a Brouter and when should one use it? Confusing!

/usr

http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211707,00.html

skully93

As I understand it:

A bridge is used to tie two different networks (or network segments) together and make them act as one. This was used more to either tie 2 networks together that are different types (like token ring and ethernet)

A router proper will route packets based on mac address or whatnot.

You'd honestly be hard pressed to find a bridge in a newer network, but they are out there.

Hope that helps.

keatron

You can sometimes find bridges in new installation. It all depends on needed functionality. The key to understanding these different devices is learning and remembering what layer of the OSI model the operate on. For the most part, the higher the layer, the more intelligent the device is. Bridges work at layer two, they can decipher MAC Addresses from packets. Routers work at layer 3 (network layer) so they can dig deeper into the packet and examine IP addresses. Just to add clarity, repeaters work at layer 1, they can only "repeat" or amplify electrical signals.

In most small to medium sized LANs or WANs you probably won't find bridges, but they still exist in enterprise grade installations.

sainth

A simple explanation for that is that a bridge will segment a collision domain, please remember that switches is the same with the bridge, the only difference is that a switch has a multiple port and the router is for segmenting broadcast domain.

If you will attach PCs on the bridge, that will be considered as one broadcast domain, that means that if PC1 will send a broadcast signal on that network, all PC that is connected on that bridge (switch) will recieve that message.

For the router, the job of the router is to segment the broadcast domain, as it was mention above, routers are more intelligent than bridge, the router can now decide if a broadcast signal will be transferred to the other network. Routers can also be use as firewall, it can filter packets or it can decide what packet can go through.

Network 1

> router <

Network 2
192.168.10.0 10.168.10.0

I hope that this help you, I wish I could explain it further

sainth

RamsesK

it was confusing me too, but i just focus on one thing to learn, here is all clear and is right, there are many places that explain the same thing and confuse ppl like me

http://www.techexams.net/technotes/networkplus/networkcomponents.shtml

Network+ N10-003 TechNotes wrote:

- Switches have more ports than bridges. Switches are meant to replace hubs and improve network performance by creating a separate collision domain per port.
- Bridges switch in software whereas switches switch in hardware (integrated circuits).
- Switches offer more variance in speed; an individual port can be assigned 10 Mb/s, 100 Mb/s, 1 Gb/s or even more.

hope that helps!

Zephium

A "brouter" is the combination of a router and a bridge in one device that shares the features of both of them. The advantage of using a brouter is that it allows more flexibility at a lesser cost then having an individual router and bridge.

fadhil

fine; A brouter is a device that combines the functionality of router and bridge(brouter= bridge and router). It routes the packets and if it can't, it bridge it.