This is one of multiple questions from my CC a course for this particular question I've had a lot of
queries and a lot of students have debated the answer with me.
So what I'm going to do in this video is demonstrate what actually happens using ostinato.
So I'm going to generate frames as per this question and show you what actually happens.
So in the quiz question I've got four PCs PC one PC to PC three and PC four with these MAC addresses
configured and the MAC address table of the switch has the address configured.
If the switch in the image receives a frame with the destination port of four zeros followed by four
ones followed by four ones from PC four out of which ports will the frame be sent.
In other words if the switch receives a frame with the destination MAC address of PC one from PC four
out of which ports will the frame be sent.
Notice again that the MAC address table.
Or to use another Cecka term they can table all content accessible memory table has the MAC address
in the table associated with port 2.
So out of which port will the frame be sent.
What do you think.
OK so let's verify what's going to happen.
I've replicated the quiz question in ingenius 3 I've got a single switch
and at the moment in the MAC address table of the switch we have the MAC address associated with gigabit
0 1.
In other words very similar to the quiz question we also have for PCs configured with the relevant MAC
addresses.
So this is the MAC address of PC 1.
This is the MAC address of PC to
Mac address a PC three and MAC address of PC full.
So in other words the MAC addresses of these four PCs is configured per the scenario.
Ostinato allows us to generate arbitrary frames.
In other words we can create any kind of frame that we want.
So in the question we asked are what happens when PC for sins frames to the destination MAC address.
So what I'll do is connect to the console or PC for and I'll open up to you and all the.
So what I can do here is generate a news stream or create a new traffic flow through this application.
So we'll be able to properly test what's going to happen.
So money is set to Ethernet to IP version for at least three TCAP lay layer for.
And what I'm going to do is set the destination MAC address per hour question.
So we asked again what happens when PC for since traffic to the destination MAC address.
So that's the destination MAC address configured.
What I'll do is send 100 packets.
So again destination MAC address is as follows.
It's an a two frame IP version for at least three.
It's going to be TCAP with some payload data.
So what I'll do before I start the traffic flow is capture traffic on could give it 00 kept capture
traffic on gigabit 0 1 and capture traffic on gigabit.
0 2 of the switch
so we'll be able to see what happens on this link this link and this link for traffic sent by host for
world traffic out of all ports.
Well it got a port one port to port tree port 1 2 and 3 pt. 1 3.
What's going to happen with a traffic.
So the MAC address of the switch once again only contains the entry.
So what I'll do now is start sending frame's from ostinato.
You can see the frame sent is incrementing about 6 7 frame S..
So let's have a look at gigabit 00 or filter for TCAP frames.
And as you can see we are receiving frames to that destination MAC address.
What about gigabit.
0 1 filter for TZP frames.
We are also receiving frames to that destination MAC address on gigabit.
0 1 What about to give it a zero or two full to 4 TZP.
We are also receiving frames on could give it to 0 2 for traffic destined to that MAC address.
Now the frames are obviously being sent on this link to the switch.
And we can see that here on gigabit is 0 3.
So frame's hit the switch and are flooded out of all ports.
Even though we've got to this entry in the MAC address table the switch is now learnt about a MAC address
0 on gigabit 0 or 3.
And that's because in ostinato we out the source MAC address as a bunch of zeros.
What's important to note is that traffic is being flooded out of all ports except the port in which
it was received.
And that's because it's going to an unknown MAC address.
Unicast frames are flooded out of all ports except to the port in which they arrive.
So no answer to this question out of which ports will the frames be sent.
It will be sent out of port one two and three.
And that's because in this diagram P.S. 1 2 and 3 are connected to ports 1 2 and 3 PC 4 is connected
to port 4 when PC 4 sends traffic to the MAC address.
It's flooded out of all ports except to the port in which it arrived some hoping that that demonstrates
practically how switches work.
Notice once again my why a shot captures
showing traffic on all ports.
The frame is being flooded out of every port so it's received on gigabit series 3 and is then flooded
out of every other port.
It's not flooded back out of the port that it was received but it's flooded out of every other port.
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