In a similar way to our previous example let's assume that C replies to a CC sends a frame to the bridge.
The bridge will read the source MAC address in the frame and then update its MAC address table with
that information.
So the bridge now knows that C is on port 3 as well as knowing that atheism pulled one because it learnt
that from the previous frame and now unlike a hub the bridge does not forward the frame of all ports.
The destination address in the frame is.
The bridge knows that MAC address stays on port 1 so it only forwards the frame out of port 1.
The frame from C therefore only goes out of port 1.
It's not sent out of port to port 4 because the bridge knows that A is on port 1.
So what does this mean.
All subsequent frames from ANC will only use port 1 in 3.
In other words if a sends a nother frame to see it will only go to Port 3.
This is because the MAC addresses of A and C are in the MAC address table and the bridgeable for traffic
based on entries in the MAC address table B and D are no longer receiving frames between A and C frames
from C to A.
Arriving on port three will go to port 1 and frame's from ATC arriving on port one will be sent out
to port 3 day for a and c can have a conversation independently of B and D B and D are no longer receiving
frames S..
Between A and C the frames between A and C are contained between ports 1 and 3.
No bandwidth is used on port 2 and 4 when traffic is sent between A and C devices b and d do not receive
any frames S..
Between A and C and therefore avoid unnecessary processing of frames not destined to themselves.
Bandwidth is being conserved.
Devices are not unnecessarily processing traffic not destined to them and thus bridges have major advantages
over hubs over time.
The bridge will learn where all mac addresses are.
So the bridge will learn that I use import one BS on Portie seasoned port 3 and Ds on port 4.
That means that over time B and D can have a conversation independently of A in C..
The two conversations do not affect each other frames from each conversation.
Do not interfere with the other conversation.
Pay for Biondi can communicate at the same time as a in C.
Now continuing with the advantages of bridges each port is a different collision domain so a collision
on port 1 will not affect port 3.
Each interface on a bridge is a separate collision domain.
So in this example we have one two three four collision domains.
If a and b were having a conversation and a collision took place on port three it will not affect a
and b they wouldn't even realize that there was a collision in the network.
Now in this typology we have a hub connected to port 4 of the bridge.
A hub is a single collision domain so any collisions that take place on the hub will affect two devices
connected to the hub but will not affect other devices elsewhere in the topology.
So if there was a collision on the hub it would affect host E and host D but it would not affect host
a C and B.
The problem with collisions is that if a collision takes place the devices have to back off for a random
period of time and then they need to try and access the network again.
So if these devices DNP are in a single collision domain the bandwidth and throughput that they have
is lower than these devices which are in a separate collision domain by themselves a C and B have a
dedicated link.
They are on a single broadcast domain and single collision domain DNG however are sharing bandwidth
because they connected to a hub host a C and B are on separate collision domains.
Now it's important to remember that a bridge is still a single broadcast domain so if a sent a broadcast
it would be received by everyone in this typology.
All devices will receive the broadcast and in some cases that's a good thing but in most cases it's
not in networking we typically want to restrict or contain broadcast traffic when there are too many
broadcasts in the network.
You can slow down all devices on the network and in the worst cases it will bring your network to its
knees.
In other words your network will just break and not function.
If you have what's called a broadcast storm bridges once again process information in software rather
than in hardware and they tend to be slow in comparison to devices such as switches which process frames
in hardware the number of ports on a bridge is also limited when compared to switches in todays environments.
Switches have essentially replaced bridges.
But it's good for you to realize that a bridge and a switch operate in a very similar way.
So in summary a bridge is a layer 2 device in the oocyte model.
In other words it operates at the data link layer.
It's more intelligent than a hub because it has a mac address table and it learns where MAC addresses
are and then adds those MAC addresses to the MAC address table and can then make intelligent decisions
on which to fall with traffic based on information learned and contained in the MAC address table.
My hubby's a physical device that simply repeat signals out of all ports except the ports in which the
traffic was received.
A bridge will flood a frame out of all ports when it doesn't.
No way to send the frame.
In other words it hasn't learned where the destination MAC address is.
It will also flood broadcasts out of all ports so each port on a bridge is a separate collision domain
but a bridge is still a single broadcast domain switches are very similar to bridges as they both reside
at least to where the data link layer of the overside model.
The big advantage of switching when compared to bridging is that processing can be done in a hot way
using what are called A-6 or application specific integrated circuits.
The number of ports supported by switches is also a lot higher.
Hundreds of ports are supported on certain switches where as with bridges you are limited to a few ports
switches are able to do this because processing is done in hardware and in actual fact these days processing
is done at wire speed which means that there is no degradation of performance between two devices when
they are connected via a switch.
In other words switches can move traffic from one port to another port at the same speed as if they
weren't there.
They can process and switch frames from one port to another port without slowing the frame down.
So here's a quick comparison between switches and bridges switches process and Hadaway using A-6 Brydges
process in software and are therefore a lot slower switcher support many ports bridges are limited in
the number of ports that they support.
Bridges have been replaced by switches in todays networks.