All language subtitles for Free-CCNA-CDP-LLDP-Day-36-CCNA-200-301-Complete-Course_en

This is a free, complete course for the CCNA.

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In this video we will cover two Layer 2 discovery\n

You might not have heard of a Layer 2 discovery\n

CDP and LLDP are exam topic 2.3, which says\n

2 discovery protocols CDP and LLDP.

CDP and LLDP are important topics for the\n

to absorb compared to topics like ACLs, IPv6,\nand OSPF.

So, hopefully this video will be a little\neasier to get through.

Here’s what we’ll cover in this video.

First I’ll give a brief overview of Layer\n2 discovery protocols.

Then I’ll cover Cisco Discovery Protocol,\nCDP.

Finally I’ll cover Link Layer Discovery\nProtocol, LLDP.

CDP and LLDP are very similar in terms of\n

Watch until the end of today’s video for\n

ExSim simulates the style and difficulty of\n

exams, and I highly recommend ExSim to anyone\n

Let’s get started with a brief intro to\n

Layer 2 discovery protocols such as CDP and\n

information about, neighboring (connected)\ndevices.

They are called ‘Layer 2’ discovery protocols\n

Layer 2, they don’t use IP addresses.

We’ll look at some Wireshark captures later,\n

inside of the frames sent by CDP and LLDP.

Although they are Layer 2 discovery protocols,\n

The shared information includes host name,\n

CDP is a Cisco proprietary protocol, developed\n

LLDP is an industry standard protocol, IEEE\n802.1AB.

So, if your network uses only Cisco devices\nCDP is fine.

However if there is a mix of vendors, for\n

Palo Alto firewalls, you will have to use\n

However, because these protocols share information\n

be considered a security risk and are often\nnot used.

It’s up to the network engineer or admin\n

At my workplace, for example, we always disable\n

To demonstrate how these protocols work, here\n

R1 will periodically send frames to SW1, telling\n

type, interface ID, IP address, etc.

SW1 will do the same, periodically sending\nframes to R1.

Note that SW1 doesn’t include an IP address\n

Its interface doesn’t have an IP address.

So let’s move on to talk about CDP specifically.

To repeat, CDP is a Cisco proprietary protocol.

It is enabled on Cisco devices by default.

For example Cisco routers, Cisco switches,\n

All of these devices have CDP enabled by default.

CDP messages are periodically sent to multicast\n

Remember that MAC address, it will be in the\nflashcards.

I know the MAC addresses used by different\n

The Anki flashcards are very helpful for this.

You can add a specific tag to these MAC address\n

This will help you remember all of these MAC\n

Anyway, if you want to learn Anki functions\n

Because the messages use a multicast MAC address\n

multiple devices, but it isn’t.

When a device receives a CDP message, it processes\n

It does not forward it to other devices.

So, only directly connected neighbors can\nbecome CDP neighbors.

By default, CDP messages are sent once every\n

These are the messages that contain the information\n

in the previous When a device receives these\n

adds an entry for the device in its CDP neighbor\ntable.

If a neighbor is disconnected, there is a\n

So, if a message isn’t received from a neighbor\n

This makes sure the CDP neighbor table doesn’t\n

to be connected, but no longer are.

CDP version 2 messages are sent by default.

There are two versions of CDP, version 1 and\n

CDP version 1 is very old so you’ll probably\n

You don’t need to know the differences between\n

2 provides a few more advanced features like\n

Okay let’s get right into the CLI to see\n

To demonstrate CDP, as well as LLDP later,\n

Two routers and two multilayer switches, although\n

Before looking at the CDP neighbor table,\n

SHOW CDP tells us the CDP timer, 60 seconds\n

by default, and it also shows which version\n

Note that if CDP isn’t enabled on the device,\n

try to use the SHOW CDP command: CDP is not\nenabled.

Okay, next I used the command SHOW CDP TRAFFIC.

This command tells us how many CDP packets,\n

At the time that I used this command, R1 had\n

messages, and all of those messages were CDP\nversion 2 messages.

Finally, you can use the SHOW CDP INTERFACE\n

You can also specify a certain interface when\n

SHOW CDP INTERFACE you’ll get information\nabout all interfaces.

Here you can see the info for G0/0.

You can see the same CDP message timer and\n

ARPA is actually a type of Ethernet encapsulation.

I haven’t talked about the different types\n

that’s beyond the scope of the CCNA, but\n

sure some of you would be wondering about\nit.

This type of Ethernet is also known as Ethernet\n

Okay, finally down here you can see a basic\n

and how many interfaces are in an up state\nand a down state.

So, remember these three commands, SHOW CDP,\n

Finally let’s look at the CDP neighbor table.

Here it is, on R1 I used the command SHOW\n

Let’s look at what you can learn from this\ncommand.

First, the ‘device ID’ column lists the\n

So, R1 has received CDP messages from SW1\nand R2.

Next is the ‘local interface’ column.

This states the interface on the local device,\non R1.

So, if we didn’t have a proper network diagram\n

to which interface on R1, we can use this\ncommand.

SW1 is connected to R1’s G0/0 interface,\n

as shown in the network diagram below.

This will reset to 180 each time R1 receives\n

With the default timers, it should count down\n

and reset it to 180, and that cycle will repeat.

If this timer reaches 0, the neighbor will\n

Next is the ‘capability’ column.

This helps you identify what kind of device\n

For example, SW1 has the letters R, S, and\nI.

First off, let me point out that I means IGMP.

This is related to multicast and is beyond\n

Then, R means router and S means switch.

Switch is obvious, SW1 is a switch, but why\nrouter?

It’s because this is a multilayer switch,\n

That’s why it’s listed as both a router\nand a switch.

It has R and B in its capability column.

Once again, R stands for router, which is\n

And B means ‘source route bridge’.

This is another thing that isn’t necessary\n

So, I recommend just remembering R for router\nand S for switch.

This displays the model of the neighboring\ndevice.

As you know, Cisco has various models of routers,\n

However, for these lessons I use virtual devices\n

is displayed here, since they aren’t physical\ndevices.

So, let’s refer to Packet Tracer which actually\n

For example, in the Packet Tracer network\n

router, R2, and a catalyst 2960 series switch,\nSW1.

Okay, last column is ‘port ID’.

This tells you the port ID on the neighboring\ndevice.

So, R1 is connected to SW1’s G0/0 interface\n

Make sure you know the difference between\n

on this device, and the ‘port ID’ field,\n

Okay, those are all of the fields of SHOW\n

To view that additional information you can\n

As you can see, more information is displayed\nfor each neighbor.

For example, here’s SW1’s entry.

Some of the information you can see here that\n

NEIGHBORS command is the software version,\n

Because SW1 is a switch, you can also see\nVTP information here.

This is something CDP can do but LLDP can’t.

VTP is a Cisco proprietary protocol, so only\n

You can also see the native VLAN of SW1’s\n

The duplex setting of SW1’s interface is\ndisplayed, also.

So, with these last two fields CDP helps identify\n

Actually, if a mismatch is found CDP will\n

I just wanted to point out that you can see\n

SW1 doesn’t have any IP addresses, so none\n

DETAIL command lets you view the neighbor’s\nIP address.

Now, if the device has a lot of CDP neighbors\n

However, there is another command which lets\n

That is this command, SHOW CDP ENTRY, followed\n

The output here is exactly the same as in\n

Here’s a brief summary of each of the commands\n

I won’t go over them individually, feel\n

Because CDP is enabled by default, if you\n

have to do any configuration, you can just\n

But now let’s take a look at some basic\nCDP configurations.

As I just said, CDP is globally enabled by\n

Each interface also has CDP enabled by default.

If you want to enable or disable CDP globally,\n

Use CDP RUN to enable it, which is default,\n

To enable CDP on an interface, which is the\n

in front of the command to disable it.

These commands are done from interface config\nmode.

You can configure the CDP timer, how often\n

command from global config mode.

You can also configure the holdtime with CDP\nHOLDTIME.

And you can enable CDP version 2, which is\n

or use NO in front of the command to disable\n

You’ll probably never use that last command,\n

So, these are the CDP configuration commands\n

CDP RUN, CDP ENABLE, CDP TIMER, CDP HOLDTIME,\n

Finally let’s move on to LLDP, Link Layer\nDiscovery Protocol.

LLDP is an industry standard protocol, so\n

CDP was the original, and LLDP was later invented\n

It is usually disabled on Cisco devices by\n

A device can run CDP and LLDP at the same\n

them, although usually you’ll just use one.

Here’s another MAC address to remember.

LLDP messages are periodically sent to multicast\n

Again, use the flashcards to remember that\none.

When a device receives an LLDP message, it\n

It does not forward it to other devices.

So, only directly connected devices can become\nLLDP neighbors.

By default, LLDP messages are sent once every\n

LLDP’s default holdtime is 120 seconds.

LLDP also has an additional timer called the\n

I don’t think you need to know this for\n

If LLDP is enabled, either globally or on\n

the actual initialization of LLDP, and the\n

I believe the purpose of this timer is to\n

is rapidly enabled or disabled for some reason.

So, the device won’t send LLDP messages\n

is enabled, it will wait for the initialization\ntimer to expire.

As I said, you probably don’t have to know\n

in the output of the commands I’m going\n

Because LLDP is disabled by default, before\n

the configuration commands you should know\nfor LLDP.

To review, LLDP is usually globally disabled\n

So, to enable LLDP you need to enable it globally\n

You’ll see that the interface configuration\n

To enable it globally use LLDP RUN.

This is the same as CDP, just replace the\nword CDP with LLDP.

If you want to disable it again after, use\n

Now the interface configurations.

To enable LLDP transmissions, tx, on an interface,\n

This causes the interface to start sending\nLLDP messages.

However, it won’t receive LLDP messages,\n

To enable LLDP in the receive direction, rx,\n

So, CDP had only one command, CDP ENABLE which\n

In LLDP, you need to use two separate commands.

But still, the configuration is quite simple.

Now let’s see how to configure each LLDP\ntimer.

The timer used to send messages is configured\n

The LLDP holdtime is configured with LLDP\n

Finally, you can configure the LLDP reinitialization\n

with LLDP REINIT, then the timer in seconds.

So, these commands are all fairly similar\n

is the interface configuration.

Make sure you enable both TRANSMIT and RECEIVE,\n

to only be able to send or receive, not send\n

So, I’ve enabled LLDP on all of these devices\n

mode, and LLDP TRANSMIT and RECEIVE on all\ninterfaces.

They are now running both CDP and LLDP.

Usually LLDP would be used in a multi-vendor\n

good enough for our purposes, to demonstrate\n

So, let’s check out some LLDP show commands,\n

First, SHOW LLDP gives the same information\n

It shows that LLDP is enabled, and displays\n

at the default settings of 30, 120, and 2\nseconds.

Then SHOW LLDP TRAFFIC, similar to SHOW CDP\n

frames were sent and received.

In this case I used the command quickly after\n

and only 3 have been received by R1.

Then I used SHOW LLDP INTERFACE.

This shows whether TRANSMIT and RECEIVE are\n

well as the current Tx and Rx state.

For example, for G0/0 both Tx and Rx are enabled.

The Tx state is IDLE, it’s waiting before\n

And the Rx state is WAIT FOR FRAME.

It’s waiting to receive the next LLDP frame\nfrom SW1.

Okay, so those commands are very similar to\n

some differences in the output.

Now let’s check out R1’s LLDP neighbor\ntable.

Here’s R1’s LLDP neighbor table, the command\n

First up, the device ID, the host name, of\n

Just like in SHOW CDP NEIGHBORS, this is the\n

This is a little different than in SHOW CDP\nNEIGHBORS.

In SHOW CDP NEIGHBORS, you could watch the\n

to 180 when a CDP message is received.

However SHOW LLDP NEIGHBORS simply displays\n

It won’t count down as R1 waits for an LLDP\n

The output here is a little odd.

SW1 shows nothing, and R2 shows R. R means\n

However, why doesn’t the switch capability\ndisplay for SW1?

Actually, there is no ‘SWITCH’ capability\ncode.

Instead, LLDP uses B for Bridge.

Remember I told you, in the spanning tree\n

Well here’s another case of that.

However, B isn’t displaying for SW1.

I think this is just because I’m running\n

detecting that SW1 is an active switch, but\n

DETAIL you will see this bridge code for SW1.

Okay, and just like in SHOW CDP NEIGHBORS,\n

R1 is connected to SW1’s G0/0 interface\nand R2’s G0/0 interface.

So, this command is very similar to SHOW CDP\n

Okay, here’s SHOW LLDP NEIGHBORS DETAIL\non R1.

The output is too long to show on one screen,\n

It gives us additional information like the\n

We can also see the ‘time remaining’.

This is the holdtime, if you want to actually\n

have to use the DETAIL version of the command.

And here is the main thing I want to show\nyou.

CDP had one field for the device’s capabilities,\n

‘System capabilities’ and ‘enabled capabilities’.

If you look at system capabilities, you can\n

So, this is what you would expect, because\n

It has the functions of both a router and\na switch.

However, in this case the ‘enabled capabilities’\n

so none of SW1’s capabilities are enabled.

If we use the IP ROUTING command on SW1, SW1’s\n

‘R’ from ‘system capabilities’ will\n

However, I think the reason ‘B’ isn’t\n

is simply because SW1 is a virtual device\n

You don’t have to worry about these details,\n

Note that this command doesn’t display VTP\n

VTP is a Cisco-proprietary protocol, so only\n

The industry-standard LLDP can’t.

Okay, just like for CDP there is a command\n

as SHOW LLDP NEIGHBORS DETAIL, but for a single\n

That command is SHOW LLDP ENTRY, followed\n

By the way, before using this command I enabled\n

for Router, is displayed next to ‘enabled\ncapabilities’ for SW1.

Here’s the same SHOW command summary as\n

The commands are the same, just replace the\nword CDP with LLDP.

The output for these commands is similar to\n

Pause the video if you want to review these\n

Let’s briefly look at a couple Wireshark\n

First, this is a CDP message sent from R1\nto SW1.

Notice the CDP destination MAC address, 0100.0CCC.CCCC.

But notice that Wireshark describes this destination\n

That’s because this same multicast MAC address\n

Now, here’s the actual CDP information.

You can see here that CDP version 2 is being\nused.

The TTL, time to live, is actually the CDP\nholdtime.

Here are some other fields such as the device\n

platform, addresses, and port ID.

I could expand each of these fields in Wireshark\n

So I just expanded the capabilities field,\n

and ‘Source Route Bridge’, those are the\ncapabilities of R1.

Finally, notice that there is no IP packet\n

These Layer 2 discovery protocols don’t\n

And here’s an LLDP frame capture, this time\n

First up, here’s the destination MAC address\n

And here’s the actual LLDP information.

The time to live, TTL, is the LLDP holdtime\n

name, the host name, of the device which sent\nthis message, SW1.

Here’s the LLDP capabilities field.

Just like we saw before, SW1’s capabilities\n

Okay, you don’t have to look into these\n

to show you some real examples of CDP and\nLLDP messages.

Before moving on to the quiz let’s review\n

First I gave a brief intro to Layer 2 discovery\n

Basically, they enable directly connected\n

each other such as host name, device type,\n

They can be very useful and convenient, but\n

a security risk because of the information\n

So, many network admins choose to disable\n

Then I introduced CDP, Cisco’s Layer 2 discovery\nprotocol.

After that I introduced LLDP, which was developed\n

LLDP is supported by many vendors, so if your\n

Alto, Fortinet, whatever, you’ll have to\nuse LLDP, not CDP.

Make sure to watch until the end of the quiz\n

ExSim for CCNA, the best practice exams for\n

Okay, let’s move on to the quiz.

Which of the following commands show the configured\nCDP timers?

Pause the video to think about your answers,\nselect two.

The answers are A and C. Both of these commands\n

D, SHOW CDP NEIGHBORS does show the current\n

for a CDP message from its neighbor, but it\n

It also doesn’t display the CDP message\n

Which of the following commands represent\nthe default CDP state?

C, CDP ENABLE, from interface config mode.

Pause the video to think about your answers,\nselect two.

The answers are C and D. CDP ENABLE enables\n

D sets the CDP message timer to 60 seconds,\n

A, NO CDP RUN, disables CDP on the router,\n

B, CDP HOLDTIME 120 sets the hold time to\n

The default CDP holdtime is 180 seconds.

You issue the show lldp entry SW1 command\non R1.

R1’s neighbor SW1 is a multilayer switch.

What do you expect to see in the ‘system\n

Pause the video to think about your answer.

The answer is B, System Capabilities: B,R.\n

Because SW1 is a multilayer switch, it has\n

S, as shown in options C and D, means switch\n

Okay, let’s go to question 4.

Which of the following statements about LLDP\nare true?

Pause the video now, read each option, and\n

Okay, the correct answers are B and F. When\n

TRANSMIT, Tx, and RECEIVE, Rx, separately\non each interface.

And LLDP can be used to learn the OS version\n

The other options are incorrect statements\nabout LLDP.

LLDP is an industry standard protocol, so\nA is incorrect.

Its default message timer is 30 seconds, so\nC is incorrect.

It can’t be used to learn the OSPF settings\n

And it can’t be used to learn the VTP settings\n

Which interface on R2 is SW2 connected to?

Is it G0/0, G0/1, G0/2, or G0/3?

Pause the video to examine R2’s CDP neighbor\n

It is shown here, in the local interface column\nof the output.

This shows the interface on R2 that SW2 is\nconnected to.

Okay, that’s all for the quiz.

Now let’s try a bonus question from Boson\n

Okay here's today's Boson ExSim practice question.

You issue the following command on your router.

Which of the following information will be\ndisplayed?

A, the IP address of the neighboring device.

B, the interface on the neighboring device\n

C, The device ID of the neighboring device.

D, the software version running on the neighboring\ndevice.

E, the interface on RouterA that is connected\n

Or F, the capabilities and product number\n

Okay, pause the video now to think about your\nanswer.

Let's go through one by one and see which\nanswers are correct.

So A, the IP address of the neighboring device.

I think that is not displayed by SHOW CDP\nNEIGHBORS.

To view that you have to use SHOW CDP NEIGHBORS\n

B, the interface on the neighboring device\n

You can see that with SHOW CDP NEIGHBORS.

C, the device ID of the neighboring device.

You can also see that, that is the host name\n

D, the software version running on the neighboring\ndevice.

I think you cannot see that in SHOW CDP NEIGHBORS.

Once again, you have to use SHOW CDP NEIGHBORS\n

system version of the neighboring device.

Okay, E, the interface on RouterA that is\n

You can see that with SHOW CDP NEIGHBORS.

The capabilities, which is like router, switch,\n

of the device, of the neighboring device.

So I think these are the four choices.

You cannot see the IP address of the neighboring\n

To view those two you have to use SHOW CDP\nNEIGHBORS DETAIL.

Okay, so to check my answer I will click down\nhere, show answer.

So, here is Boson's explanation.

You can pause the video to read their explanation,\n

Boson gives great explanations, not just why\n

each incorrect answer is incorrect.

So they are a great resource to improve your\nunderstanding.

Okay, and at the bottom there are a few references\n

This is a great book for studying for the\nCCNA.

And also some Cisco documentation about CDP\n

Okay, so that's Boson ExSim for the CCNA.

If you want to get ExSim, please follow the\n

These are by far the best practice exams for\nthe CCNA.

Once again, follow that link in the video\ndescription.

There are supplementary materials for this\nvideo.

There is a flashcard deck to use with the\nsoftware ‘Anki’.

There will also be a packet tracer practice\n

That will be in the next video.

Sign up for my mailing list via the link in\n

the flashcards and packet tracer lab files\nfor the course.

Before finishing today’s video I want to\n

To join, please click the ‘Join’ button\nunder the video.

Thank you to Magrathea, Samil, Aaron, Junhong,\n

Nasir, Erlison, Apogee, Marko, Daming, Joshua,\n

C Mohd, Mark, Yousif, Boson Software, Devin,\n

Sorry if I pronounced your name incorrectly,\n

This is the list of JCNP-level members at\n

If you signed up recently and your name isn’t\n

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