1
00:00:00,000 --> 00:00:00,031

2
00:00:00,031 --> 00:00:01,780
For this scenario,
we're going to generate

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some traffic within VLAN 200
going from PC-3 over to PC-5.

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00:00:06,820 --> 00:00:09,640
But before we do that, we'll
predict what the MAC address

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00:00:09,640 --> 00:00:13,030
tables would be on both switches
that are connected via a trunk,

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00:00:13,030 --> 00:00:15,160
and then we'll validate
it via demonstration.

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00:00:15,160 --> 00:00:17,410
So here's our task-- to
predict the MAC address tables

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00:00:17,410 --> 00:00:19,540
on switch 1 and
switch 2 after a ping

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00:00:19,540 --> 00:00:23,200
from PC-3, which is right
here, going over to PC number

10
00:00:23,200 --> 00:00:25,150
5, which is right here.

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00:00:25,150 --> 00:00:27,246
And I thought to myself,
you know what, Keith--

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that's what I call myself--

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00:00:28,370 --> 00:00:30,121
I should probably give
a moment right here

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00:00:30,121 --> 00:00:32,161
for a person who wants to
solve this on their own

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00:00:32,161 --> 00:00:33,050
a chance to do it.

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00:00:33,050 --> 00:00:34,780
So if you want to
solve this on your own

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00:00:34,780 --> 00:00:38,140
before we would do the walk
through, hit pause, solve it,

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00:00:38,140 --> 00:00:41,730
and then we'll
continue together.

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00:00:41,730 --> 00:00:44,080
[MUSIC PLAYING]

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00:00:44,080 --> 00:00:46,900

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00:00:46,900 --> 00:00:49,830
So if PC-3 does not have
an entry in the ARP cache

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00:00:49,830 --> 00:00:51,960
for the MAC address
of PC-5, it's

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00:00:51,960 --> 00:00:53,870
going to send an ARP
request as a broadcast.

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00:00:53,870 --> 00:00:56,490
That's going to come
in on port Gig 0/3,

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00:00:56,490 --> 00:00:58,260
right here on switch 1.

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00:00:58,260 --> 00:01:01,040
And that's an access
port in VLAN 200.

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00:01:01,040 --> 00:01:02,880
And the source MAC
address in that frame

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is going to be PC-3's source
MAC address ending in 6803, just

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like that, because that's
a broadcast associated

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00:01:10,070 --> 00:01:11,340
with VLAN 200.

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00:01:11,340 --> 00:01:13,320
Switch 1 doesn't
have any other access

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ports at the moment
in VLAN 200, but it

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00:01:15,360 --> 00:01:17,280
does have a trunk
that's associated with

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00:01:17,280 --> 00:01:19,270
and carrying VLAN 200 traffic.

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00:01:19,270 --> 00:01:22,410
So switch 1 tags that
frame with an 802.1Q tag,

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marking it as VLAN 200, and
sends that broadcast over

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00:01:25,440 --> 00:01:28,140
the trunk where it's
received by switch 2.

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Switch 2 on Gig 1/0
looks at that source MAC

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address, which is 6803, still
PC-3's source MAC address.

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They had the 802.1Q tag saying
it came from and is associated

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with VLAN 200.

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And switch 2 would
forward that broadcast out

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00:01:42,460 --> 00:01:45,270
to all other ports
associated with VLAN 200,

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which would include
Gig 1/2 and 1/3.

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00:01:49,050 --> 00:01:52,140
So both PC-5 and PC-6
listen to that broadcast,

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00:01:52,140 --> 00:01:55,200
they process it, but only
PC-5 is using the address

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00:01:55,200 --> 00:01:58,410
that's in the ARP
request of 10.200.0.5.

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So PC-5 will respond
back with that ARP reply.

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00:02:02,160 --> 00:02:04,850
And that goes into the
switch on port Gig 1/2.

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00:02:04,850 --> 00:02:07,320
So it will add that port
here where switch 2 now

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00:02:07,320 --> 00:02:11,700
knows the MAC address of
PC-5, which ends in 6805.

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00:02:11,700 --> 00:02:13,470
And that's associated
with VLAN 200

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00:02:13,470 --> 00:02:17,370
because the access port Gig 1/2
is associated with that VLAN.

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00:02:17,370 --> 00:02:19,650
And that reply is sent
back to the MAC address

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00:02:19,650 --> 00:02:23,370
of PC-3, which
ends in 6803, which

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00:02:23,370 --> 00:02:24,780
the switch knows where that is.

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00:02:24,780 --> 00:02:28,740
So it forwards it out this way,
also tagged with an 802.1Q tag

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00:02:28,740 --> 00:02:30,900
indicating it's
associated with VLAN 200,

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00:02:30,900 --> 00:02:33,360
which is received by switch
1, who looks at the source MAC

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00:02:33,360 --> 00:02:36,960
address, which ends in 6805,
adds that to its MAC address

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00:02:36,960 --> 00:02:39,300
table, associates that with
the port where it learned it

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00:02:39,300 --> 00:02:41,280
on, which is 0/0.

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00:02:41,280 --> 00:02:44,460
And due to the 802.1Q tag, it
knows that that MAC address is

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associated with VLAN 200.

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00:02:46,470 --> 00:02:49,800
So if these entries didn't exist
previously in the MAC address

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00:02:49,800 --> 00:02:53,107
tables after a ping
request from PC-3 to PC-5,

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00:02:53,107 --> 00:02:54,690
we would expect at
least these entries

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00:02:54,690 --> 00:02:58,030
to have been added as a result
of that network traffic.

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00:02:58,030 --> 00:03:00,560
So starting off on PC-3,
let's do a show ARP.

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00:03:00,560 --> 00:03:02,870
And let's do our
ping over to PC-5,

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00:03:02,870 --> 00:03:07,106
which is over at
10.200.0.5, and press Enter.

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00:03:07,106 --> 00:03:07,980
That's looking great.

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00:03:07,980 --> 00:03:09,690
Let's go back over
to our switches

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and verify our predictions
regarding the MAC address

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00:03:12,180 --> 00:03:13,180
tables.

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00:03:13,180 --> 00:03:16,977
So here on switch 1, we'll
do a show mac address table.

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And then we'll do the
same command down here

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00:03:18,810 --> 00:03:22,650
on switch number 2-- show mac
address dash table and press

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00:03:22,650 --> 00:03:23,460
Enter.

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00:03:23,460 --> 00:03:25,290
And that confirms
what we expected.

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00:03:25,290 --> 00:03:27,990
So we have VLAN 200 for all
the entries that we just

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00:03:27,990 --> 00:03:29,090
dynamically learned.

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00:03:29,090 --> 00:03:31,790
Switch 1 believes that 6803--

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00:03:31,790 --> 00:03:34,890
that's PC-3's address-- is
reachable on its local port

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00:03:34,890 --> 00:03:37,140
of Gig 0/3, which it is.

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00:03:37,140 --> 00:03:40,320
It also believes that the
MAC address ending in 6805,

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00:03:40,320 --> 00:03:44,790
which the PC-5, is reachable
over its trunk Gig 0/0, which

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is also accurate.

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00:03:45,940 --> 00:03:49,430
[LAUGH] And I say that as if,
wow, the switch is accurate.

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00:03:49,430 --> 00:03:50,850
No, our predictions
were accurate.

91
00:03:50,850 --> 00:03:52,350
That's the even
more important part.

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00:03:52,350 --> 00:03:54,450
And then down in
switch 2, it indicates

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00:03:54,450 --> 00:03:57,270
that 6803, which is the
MAC address of PC-3,

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00:03:57,270 --> 00:04:00,660
is reachable over the trunk
on switch 2 of Gig 1/0,

95
00:04:00,660 --> 00:04:02,260
which it is, and
that the MAC address

96
00:04:02,260 --> 00:04:08,400
6805 is reachable on the local
port of Gig 1/2 on switch 2.

97
00:04:08,400 --> 00:04:10,350
And so that validates
our predictions

98
00:04:10,350 --> 00:04:13,080
regarding the MAC address table
entries that were dynamically

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00:04:13,080 --> 00:04:15,810
created as a result of
the specific network

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00:04:15,810 --> 00:04:19,920
traffic between PC-3 and PC-5.

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00:04:19,920 --> 00:04:22,089
And here's what I'm going
to invite you to do.

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00:04:22,089 --> 00:04:24,047
I'd like you to take this
final scenario, which

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00:04:24,047 --> 00:04:27,220
is a ping from PC-1 to PC-2,
which we've done previously

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00:04:27,220 --> 00:04:27,990
on its own.

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00:04:27,990 --> 00:04:32,160
But combine it with a ping from
PC-3 to PC-5, which we just

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00:04:32,160 --> 00:04:34,680
did, and as a result
of both those elements

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00:04:34,680 --> 00:04:37,777
happening, the entries that
we would expect to see.

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00:04:37,777 --> 00:04:39,360
And to reinforce the
results after you

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00:04:39,360 --> 00:04:40,943
make your predictions,
you can go back

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00:04:40,943 --> 00:04:42,820
to those previous Nuggets
where we generated

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00:04:42,820 --> 00:04:44,580
that specific traffic,
just to verify

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00:04:44,580 --> 00:04:46,860
that your predictions
match up with what

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00:04:46,860 --> 00:04:48,240
the switch is delivering.

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00:04:48,240 --> 00:04:49,620
So have some fun with that.

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00:04:49,620 --> 00:04:52,500
Meanwhile, I hope this has
been informative for you.

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And I'd like to thank
you for viewing.