All language subtitles for 4. Answers Part 3 Broadcast and Collision domains

In question 5 we we're told to assume that one MAC address is empty.

We can verify that by looking at the output of the show MAC address table command on the switch as we

can see here the MAC address table is empty.

We asked when P.S. five pings P.S. eight what type of packet is sent to the switch initially.

And can we prove it.

So

IP config on P.S. 5 shows us the IP address of P.S. 5 10 1 1 5.

P.S. 8

has IP address 10 1 1 8.

So what kind of frame or what kind of packet is sent to the switch when using terms such as frames and

packets once again are we referring to layer 2 or Layer 3 or Layer 4 of the other side model.

So what I'll do on P.S. 5 is paying 10 1 1 8 before I do that.

Notice the OP cache is empty.

On P.S. 5 if it had just a rebooted the OP cache would be empty.

Something to send two pings into the network we can see that the first packet that was generated is

an all package looking at the actual packet or frame we can see that add layer to the frame has a destination

address of a broadcast.

That type of package at least 3 is OP so in the Layer 3 headers we can see that this is an off packet

requesting the MAC address of host with IP address 10 1 1 8 so the Ethernet type is 0 6 0 8 0 6.

In other words it's an op packet capture forward

and before I continue the answer to Question 5 is this is an op packet it's a broadcast packet we can

see that again by looking at the inbound PD you honor the switch notice destination address is a broadcast

who receives the packet because it's a broadcast it's going to be flooded to the other devices in the

network and then P.S. 6 and P.S. 7 are going to drop it because of the packet is not destined to them.

So the answer for question 6 is.

P.S. 6 P.S. 7 and PCH will receive the packet.

Now here's where things change.

Who receives the you return packet.

So here we've got our op reply on the inbound PD U to the switch.

We can see that the target mac address is this.

That's the MAC address of P.S. 5.

So the MAC address is actually written into the frame.

This is a unique cost packet center from P.S. 8 to P.S. 5.

It's not a broadcast unlike the OP request to notice what happens now.

The packet is only sent to P.S. 5.

It's not flooded out of all ports so the only piece that receives it is P.S. 5 that is different to

our previous example where P.S. One P.S. 2 and P.S. 3 received the return traffic and notice the difference

in question 8 when Pink traffic is sent from P.S. 5 to PCH who receives it.

So here's

ICMP request or echo request message we can see that it's ICMP destination MAC address is P.S. 8.

Source MAC address is P.S. 5 source IP address is.

P.S. 5 destination IP address is PCH.

So notice now that the packet is only sent to PCH so that's a very different to what we saw when we

were using a hub a switch is different to a hub in that it has a separate collision domain on every

port so when packets are sent from P.S. 5 to PCH they are sent directly between the devices they don't

get flooded to the other pieces in the network.

That is very different to a hub so to prove that what I'll do is populate or the OP cache of P.S. 6

so I'll get it to ping.

P.S. 8 and I'll run this in real time so if we look at to the OP cache of P.S. 6 OP caches populated

the same is true on P.S. 5.

So both.

P.S. 5 and P.S. 6 know the MAC address of PCH I'll change this to simulation mode.

And I'll get both of these pieces to ping PCH

both of them are sending ICMP packets.

They both get sent to the switch.

And notice the first one is sent to PCH and then the second one is sent to PCH.

We don't end up with a collision so the switcher cashes the package and allows the communication and

to show you this in a different way.

What I'll do is get pissy 5 to ping PCH

but get to P.S. six to ping P.S. seven CPC five is pinging pieces eight pieces six is pinging pieces

seven in this case pieces six and needs to ARP for the mac address of P.S. seven.

Notice however that there is no collision taking place.

So now notice the OP cache of pieces 6 is populated with the MAC address of both P.S. 7 and PCH so I'll

run that again

and I need to be in simulation mode to do that.

So they both are sending ICMP packets

these are unit costs.

They are not broadcasts notice of the destination of this frame is P.S. 7 destination of this frame

is P.S. 8 both packets can be sent and received by the switch without interference from the other conversation

so the pieces can communicate now without collisions and they are essentially separated from the other

conversation the conversation between P.S. 5 and P.S. 8 happens independently of the conversation between

P.S. 7 and P.S. 6.

We have 4 collision domains here

a hub is a single collision domain a switch has a collision domain per interface but again if P.S. 5

sent a broadcast

the broadcast

would be forwarded to all devices in the network.

This is a layer to switch.

It's going to flood that broadcast out of all ports so everyone is going to receive the broadcast and

everyone is going to have to reply back to that broadcast.

Packet tracing is not perfect software but it allows you to visually see how traffic flows in the network

and to learn how to answer questions such as these.

So when studying for the CCMA exam you can use packet tracer to learn how traffic flows to learn what

frames look like what packets looked like what segments looked like and it helps you essentially become

a better network engineer.

So were you able to answer these questions.

Do you understand how data flows in a network when you have a switch or when you have a hub.

Make sure that you understand how data flows through networks.