For this scenario, we're going to generate
some traffic within VLAN 200 going from PC-3 over to PC-5.
But before we do that, we'll predict what the MAC address
tables would be on both switches that are connected via a trunk,
and then we'll validate it via demonstration.
So here's our task-- to predict the MAC address tables
on switch 1 and switch 2 after a ping
from PC-3, which is right here, going over to PC number
5, which is right here.
And I thought to myself, you know what, Keith--
that's what I call myself--
I should probably give a moment right here
for a person who wants to solve this on their own
a chance to do it.
So if you want to solve this on your own
before we would do the walk through, hit pause, solve it,
and then we'll continue together.
[MUSIC PLAYING]
So if PC-3 does not have an entry in the ARP cache
for the MAC address of PC-5, it's
going to send an ARP request as a broadcast.
That's going to come in on port Gig 0/3,
right here on switch 1.
And that's an access port in VLAN 200.
And the source MAC address in that frame
is going to be PC-3's source MAC address ending in 6803, just
like that, because that's a broadcast associated
with VLAN 200.
Switch 1 doesn't have any other access
ports at the moment in VLAN 200, but it
does have a trunk that's associated with
and carrying VLAN 200 traffic.
So switch 1 tags that frame with an 802.1Q tag,
marking it as VLAN 200, and sends that broadcast over
the trunk where it's received by switch 2.
Switch 2 on Gig 1/0 looks at that source MAC
address, which is 6803, still PC-3's source MAC address.
They had the 802.1Q tag saying it came from and is associated
with VLAN 200.
And switch 2 would forward that broadcast out
to all other ports associated with VLAN 200,
which would include Gig 1/2 and 1/3.
So both PC-5 and PC-6 listen to that broadcast,
they process it, but only PC-5 is using the address
that's in the ARP request of 10.200.0.5.
So PC-5 will respond back with that ARP reply.
And that goes into the switch on port Gig 1/2.
So it will add that port here where switch 2 now
knows the MAC address of PC-5, which ends in 6805.
And that's associated with VLAN 200
because the access port Gig 1/2 is associated with that VLAN.
And that reply is sent back to the MAC address
of PC-3, which ends in 6803, which
the switch knows where that is.
So it forwards it out this way, also tagged with an 802.1Q tag
indicating it's associated with VLAN 200,
which is received by switch 1, who looks at the source MAC
address, which ends in 6805, adds that to its MAC address
table, associates that with the port where it learned it
on, which is 0/0.
And due to the 802.1Q tag, it knows that that MAC address is
associated with VLAN 200.
So if these entries didn't exist previously in the MAC address
tables after a ping request from PC-3 to PC-5,
we would expect at least these entries
to have been added as a result of that network traffic.
So starting off on PC-3, let's do a show ARP.
And let's do our ping over to PC-5,
which is over at 10.200.0.5, and press Enter.
That's looking great.
Let's go back over to our switches
and verify our predictions regarding the MAC address
tables.
So here on switch 1, we'll do a show mac address table.
And then we'll do the same command down here
on switch number 2-- show mac address dash table and press
Enter.
And that confirms what we expected.
So we have VLAN 200 for all the entries that we just
dynamically learned.
Switch 1 believes that 6803--
that's PC-3's address-- is reachable on its local port
of Gig 0/3, which it is.
It also believes that the MAC address ending in 6805,
which the PC-5, is reachable over its trunk Gig 0/0, which
is also accurate.
[LAUGH] And I say that as if, wow, the switch is accurate.
No, our predictions were accurate.
That's the even more important part.
And then down in switch 2, it indicates
that 6803, which is the MAC address of PC-3,
is reachable over the trunk on switch 2 of Gig 1/0,
which it is, and that the MAC address
6805 is reachable on the local port of Gig 1/2 on switch 2.
And so that validates our predictions
regarding the MAC address table entries that were dynamically
created as a result of the specific network
traffic between PC-3 and PC-5.
And here's what I'm going to invite you to do.
I'd like you to take this final scenario, which
is a ping from PC-1 to PC-2, which we've done previously
on its own.
But combine it with a ping from PC-3 to PC-5, which we just
did, and as a result of both those elements
happening, the entries that we would expect to see.
And to reinforce the results after you
make your predictions, you can go back
to those previous Nuggets where we generated
that specific traffic, just to verify
that your predictions match up with what
the switch is delivering.
So have some fun with that.
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.