Time
15 hours 34 minutes
Difficulty
Intermediate
CEU/CPE
16

Video Description

Port Fast lab Returning to our VLAN simulation in this lesson we demonstrate how the Port Fast enhancement feature of Spanning Tree Protocol works. For example, you'll learn whether or not routers understand BPDUs by default and what happens when the port has Spanning Tree Protocol enabled.

Video Transcription

00:04
So in our topology. Where would be used the port fast Feature
00:09
Well switch one port of zeros. Last 24
00:14
is connected to a router. One
00:16
Port F 00
00:18
switched to port at zero slash 24 is connected to a router to at 00
00:23
Switched three zeros. Last 24 is connected to
00:28
router three zeros last 24
00:31
and switch for zeros. Last 24 is connected to a router for zero slash 24.
00:37
Do routers understand bpd use or spanning tree?
00:40
Not by default? You can turn a router into a rudimentary switch, but why would you want to do that? So by default, routers do not understand BP to use. So since they don't understand spanning tree, why would we want to make rather 123 and four weights 50 seconds for spanning tree to converge before they can transmit data?
00:59
So the porch
01:02
that connect these routers or the switch ports that connect these routers can have the spanning tree port fast feature enabled.
01:10
So on switch one.
01:12
I am going to go to Port Port F zero slash 24 or interface
01:21
as you notice last 24 remember our rule of thumb to make changes to a port in the Cisco world. You have to first go to that port.
01:34
Then I'm going to say, spanning tree
01:37
port fast one word
01:38
and hit. Enter. As soon as you would enter, you get a warning.
01:42
And the warning says Port fast should only be enabled on poor connected to a single host in this case for 24 is connected to a single host. The host being rather one
01:53
connecting hubs Concentrator switches bridges to this interface when poor, fastest enable can cause temporary bridging loops.
02:00
So basically what it is saying it is a warning saying don't enable poured fast on your trunk ports
02:07
because what if you enable port fast on a trunk port? And that port was supposed to be shut down by spanning tree. It was supposed to be blocking, and now you went ahead and put it in forwarding By enabling sport fast, you could cause bridging loops.
02:23
So I went ahead and did that on switch one enabled poor fast. I'm going to save my work.
02:30
I'm gonna go to switch to and do the same enable poured fast on port 24. I'm gonna do this. Quick.
02:38
Spanning tree.
02:40
Poor fast. Save my work.
02:46
I'm going to do this on switch three.
02:53
Standing three Port fast. Save my work.
03:00
That saved my work on switch to Yes, I did.
03:02
Now on switch for I'm gonna show you something
03:07
I'm gonna pull up Switch for and I'm gonna pull up Router. For
03:14
now. I'm gonna go into writer for
03:21
and I'm gonna
03:23
bring this link up between Switch four and Router four. So switch for port F zero slash 24 router for F 00
03:34
Now, as from from previously, I had mentioned that switch points by default are enabled. They're up and running,
03:42
however, by default ports on routers.
03:46
If I go to route or four and I look at poor F 00 or interface F 00 say show interface, F zero slash zero or fast. Internet zero slash zero and I hit. Enter
04:03
route reports by default are in administratively down mode.
04:10
So by default there, shut down. I'm gonna go
04:13
do the opposite of that or I'm gonna know Shut down that port or basically bring it up.
04:18
So to make changes to a port I must first go to the port. I'm going to say configure terminal
04:27
and I'm going to say interface
04:30
fast Internet zero, slide zero. And then I'm gonna execute the no shut command.
04:36
Now, I haven't hit enter yet,
04:39
but once I hit enter
04:41
pay attention to this link.
04:45
So
04:46
I'm gonna hit Enter
04:48
and we are going to look at this link.
04:54
As you see, the link is Amber. It's not up yet because spanning tree is converging spanning tree is taking that poor true. The cycle of going through blocking, listening, learning and fording.
05:06
It will take 50 seconds for this sport
05:10
to turn green
05:12
before it can forward data traffic. However, now see, it went green.
05:17
However,
05:19
I'm gonna go back to Router for,
05:23
and I'm gonna shut that port down again.
05:26
So execute the shut down command
05:29
so it will once again say administratively down.
05:34
And I'm gonna go to switch for Port 24
05:43
interface fast Internet zero slash 24 I'm going to execute the spanning tree port. Fast command
05:51
save my work. Always Good idea.
05:56
And now I'm gonna go. No, shut this port and see how quick it comes up.
06:03
So I'm going to keep
06:06
you guys keep your eyes on this link between switch for and router for. I'm going to keep around for minimize. So you guys can see this link. I'm going to say no. Shut down and remember,
06:18
switch for port 24 here now has the spanning tree port fast command. So this should pop into forwarding and go green immediately.
06:28
Okay, here we go. And it went green immediately because the poor fast command has been executed on switch for Port 24.
06:36
I'm gonna go ahead and shut this port down again.
06:40
We will bring it up at a later part of the lab.
06:45
This completely concludes
06:46
spanning tree, poor people.
06:49
Next,
06:51
we're going to move on to
06:55
something called virtual Trunk ing Protocol.

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