All language subtitles for Free-CCNA-DHCP-Day-39-CCNA-200-301-Complete-Course_en

Welcome to Jeremy’s IT Lab. This is a free,\xa0\n

videos, please subscribe to follow along with the\xa0\n

and share the video to help spread this\xa0\n

In this video we will cover DHCP,\xa0\n

Just like DNS, DHCP is a protocol that you’re\xa0\n

aware of it. DHCP allows DHCP clients, usually end\xa0\n

learn which IP address to use from a DHCP server,\xa0\n

However DHCP allows devices to learn much more\xa0\n

video. DHCP is part of exam topics 4.3, explain\xa0\n

and 4.6, configure and verify DHCP client and\xa0\n

5.0, security fundamentals, however we’ll leave\xa0\n

Here’s what we’ll cover in this video. First\xa0\n

and why we use it. Then I’ll introduce the\xa0\n

four-message exchange that clients use\xa0\n

Then I’ll show you how to configure DHCP in\xa0\n

a DHCP client, or something called a ‘DHCP\xa0\n

all of those. Make sure to watch until\xa0\n

question from Boson Software’s ExSim for\xa0\n

Here’s a brief overview of DHCP. DHCP is used to\xa0\n

various aspects of their network\xa0\n

subnet mask, default gateway, DNS server,\xa0\n

It is an essential part of modern networks, I’m\xa0\n

when you connect a phone to WiFi, do you ask the\xa0\n

which IP address, subnet mask, default gateway,\xa0\n

we all expect that once we connect to WiFi\xa0\n

and the Internet. It’s probably the same in your\xa0\n

home router, you probably don’t need to manually\xa0\n

etc. Of course, you can do that if you want, and\xa0\n

configuration isn’t such a difficult task. However\xa0\n

Note that DHCP is typically used for ‘client’\xa0\n

Devices such as routers, servers,\xa0\n

This is because they need to have a fixed\xa0\n

If the default gateway of the network kept\xa0\n

In small networks (such as home networks) the\xa0\n

hosts in the LAN. If you have a router in your\xa0\n

for all of your devices. However in larger\xa0\n

the DHCP server is usually\xa0\na Windows or Linux server.

Now I’ll give a brief demonstration\xa0\n

which is running Windows 10. If your PC is\xa0\n

This is the ‘network and sharing center’, which\xa0\n

to select my PC’s Ethernet0 connection, which is\xa0\n

This is what you’ll see after opening it. Here\xa0\n

connection, Ethernet0. Then the properties are\xa0\n

This window opens up. Here I can confirm that\xa0\n

IP address automatically’. And down here it\xa0\n

‘Automatically’ means that my PC will use DHCP\xa0\xa0

to learn which IP address, subnet mask,\xa0\n

Let’s take a look at what was automatically\xa0\n

which you already know. First off, notice\xa0\n

If I had manually configured my PC’s\xa0\n

‘No’ would display here. And here is\xa0\n

192.168.0.167 with a /24 subnet mask. Notice that\xa0\n

It means that this PC was previously\xa0\n

Then, when it asked the server for an IP address\xa0\n

If this address was no longer available, my PC\xa0\n

However, the address was available, so my PC got\xa0\n

of DHCP, the lease time. IPCONFIG /ALL displays\xa0\n

it will expire. What exactly does this mean?\xa0\n

These leases are usually not permanent, and the\xa0\n

the lease. A client can also release the address\xa0\n

Now, I said ‘usually’ not permanent, because\xa0\n

to permanently assign IP addresses. However,\xa0\n

For example, think about a cafe that provides\xa0\n

If the IP address leases were permanent,\xa0\n

and connects to the WiFi, the customer’s devices\xa0\n

unless the client device releases it. Or how about\xa0\n

why it’s best to limit the lease time, to preserve\xa0\n

longer than the lease time, their device will\xa0\n

but if they stop using the network the IP\xa0\n

Okay, here at the bottom we can see some\xa0\n

The default gateway, DHCP server,\xa0\n

which is my home router. This\xa0\n

the home router provides all of these\xa0\n

I want to demonstrate the process that a DHCP\xa0\n

a DHCP server, but first I need to make my PC\xa0\n

again. The command in the Windows command prompt\xa0\n

/RELEASE. Now no information is displayed for the\xa0\n

just happened. My PC sent a DHCP Release message\xa0\n

IP address isn’t needed anymore. So, 192.168.0.167\xa0\n

I used Wireshark to capture\xa0\n

For the CCNA you should focus on learning the four\xa0\n

a DHCP server, which I will show you next. But\xa0\n

Of course, the message is an Ethernet frame so\xa0\n

inside, from source IP address 192.168.0.167, the\xa0\n

Inside is a UDP header, and notice the\xa0\n

DHCP servers use UDP port 67 and DHCP clients use\xa0\n

it’s the DHCP client, and the destination\xa0\n

This is different than DNS, for example, in\xa0\n

and the client uses a random ephemeral port.\xa0\n

DHCP release message. The client IP is indicated\xa0\n

DHCP has various options used for different\xa0\n

indicates what kind of DHCP message it is. And\xa0\n

part of DHCP messages, the magic cookie. Do a\xa0\n

Now that I’ve released the IP address of\xa0\n

get an IP address from the DHCP server. From the\xa0\n

/RENEW. My PC contacts the DHCP server, and\xa0\n

This process involves four\xa0\n

The first message is the DHCP Discover message.\xa0\n

Basically, it’s asking if there are any DHCP\xa0\n

needs an IP address. Let’s use Wireshark to take\xa0\n

Here it is. Here’s the Ethernet header. Notice\xa0\n

My PC doesn’t know the IP address or MAC address\xa0\n

if there is a DHCP server on the network, so\xa0\n

Here’s the IPv4 header. Notice\xa0\n

Basically, this means my PC doesn’t have an IP\xa0\n

so it’s a broadcast message. Once again,\xa0\n

client to the server, the source port is UDP\xa0\n

the actual DHCP message. You don’t need to know\xa0\n

just know their basic purpose. But here are a few\xa0\n

Bootp is actually the predecessor of DHCP, but\xa0\n

I just want to point out the value of ‘unicast’\xa0\n

message is broadcast but this field says unicast.\xa0\n

Then we can see here that the client IP\xa0\n

an IP address yet. The client MAC is also\xa0\n

notice they are different than the ones used in\xa0\n

Let me just point out this option, Requested\xa0\n

address 192.168.0.167, it requested that address\xa0\n

might grant it that same IP address again. But if\xa0\n

If this is the first time my PC is using DHCP\xa0\xa0

it won’t request an IP address like this, it\xa0\n

The next message is the DHCP Offer message, it is\xa0\n

an address for the client to use, as well as other\xa0\n

So let’s check out the DHCP\xa0\n

First off, notice the Offer is sent as a\xa0\n

since the server learned the client’s\xa0\n

It’s also unicast at Layer 3, the destination\xa0\n

This time the source and destination port\xa0\n

from the server to the client. The source\xa0\n

And here’s the Offer message. Let’s look at\xa0\n

it says unicast. When my PC sent the DHCP Discover\xa0\n

This means that the server will send its messages\xa0\n

However, that’s not always the case. The DHCP\xa0\n

either broadcast or unicast. It depends on the\xa0\n

the Offer using unicast, so it did. If my PC told\xa0\n

destination MAC of this message would be all F’s\xa0\n

At this point in the DHCP process, the\xa0\n

Some clients won’t accept unicast messages before\xa0\n

why sometimes broadcast must be used instead of\xa0\n

example option 51 indicates the lease time, option\xa0\n

and option 3 is ‘router’, which tells the client\xa0\n

to memorize these option numbers, definitely not\xa0\n

Okay, the next message is the DHCP Request\xa0\n

to the server, telling the server that it\xa0\n

This is important, there may be multiple\xa0\n

and all of them will reply to the\xa0\n

So, the client has to tell which\xa0\n

and request to use that IP address. Typically, the\xa0\n

Let’s look at that Request message in Wireshark.\xa0\xa0

The destination MAC is all Fs, so this\xa0\n

If there are multiple DHCP servers on the\xa0\n

message. One of the later fields will indicate\xa0\n

The source IP is still 0.0.0.0, since the offered\xa0\n

The destination is broadcast, 255.255.255.255.\xa0\n

server, the source port is UDP 68 and the\xa0\n

message. Here’s the flags field again, telling\xa0\n

even though the client itself uses broadcast. And\xa0\n

Notice that the server’s IP address is\xa0\n

multiple DHCP servers on the local network, this\xa0\n

Now the final message in the process, the DHCP\xa0\n

to the client, confirming that the client may\xa0\n

is received the client finally configures\xa0\n

Here’s that Ack message in Wireshark.\xa0\xa0

Notice that these messages from the server to the\xa0\n

not broadcast. Let me point out once\xa0\n

so that’s the source port, and the client uses\xa0\n

And here’s the Ack message. The Bootp flags field\xa0\n

requested unicast messages. Just like the DHCP\xa0\n

broadcast or unicast, depending on what the client\xa0\n

message. There are many different DHCP options, if\xa0\n

page lists a bunch of them, and a quick Google\xa0\n

their various functions. But that’s just\xa0\n

Here’s a quick summary of that process. A common\xa0\n

for Discover, Offer, Request, and Ack. Make\xa0\n

client to server, server to client, and also which\xa0\n

sent either broadcast or unicast. Also, here’s\xa0\n

unicast from the client to the server. There are\xa0\n

but if you know these message\xa0\n

Next let me introduce the concept of DHCP Relay.\xa0\xa0

Some network engineers might choose to\xa0\n

for its connected LANs. However, large enterprises\xa0\n

which will assign IP addresses to DHCP clients\xa0\n

If the server is centralized, it won’t receive\xa0\n

Remember, broadcast messages don’t leave the local\xa0\n

fix this you can configure a router to act as a\xa0\n

will forward the clients’ broadcast DHCP messages\xa0\n

Let me use this network to demonstrate. PC1\xa0\n

Discover message to ask DHCP servers on the\xa0\n

However, in this case R1 isn’t a DHCP server.\xa0\n

so R1 will need to forward any\xa0\n

Let me demonstrate that visually. SRV1 is a\xa0\n

PC1 broadcasts a DHCP Discover message to get an\xa0\n

message to SRV1. Notice that the source address\xa0\n

and the destination is SRV1’s IP\xa0\n

Then SRV1 replies with the DHCP Offer, sending\xa0\n

192.168.1.1. R1 then forwards it to\xa0\n

and the message is either sent unicast to PC1 or\xa0\n

and R1 relays it to SRV1. Finally SRV1 replies\xa0\n

which configures the IP address it was\xa0\n

So, that’s a quick overview of how DHCP\xa0\n

configure a DHCP relay agent, you just need\xa0\n

In the next section I’ll show you how to configure\xa0\n

Cisco router as a DHCP server, and then how to\xa0\n

Finally I’ll show you how to configure\xa0\n

So, let me show you how to configure a\xa0\n

Let’s use these two devices here, R1 and PC1. Here\xa0\n

DCHP EXCLUDED-ADDRESS command to specify a range\xa0\n

These are addresses you want to reserve,\xa0\n

the local subnet. The first address in the command\xa0\n

is the top of the range. So, this reserves all\xa0\n

This command isn’t necessary, but it’s a good idea\xa0\n

assigned to servers, network devices, or whatever.\xa0\n

the pool name, to create a DHCP pool. What is a\xa0\n

that can be assigned to DHCP clients, as well as\xa0\n

You should create a separate DHCP pool for each\xa0\n

In this case R1 is only acting as the DHCP server\xa0\n

pool. Here’s where you actually configure the\xa0\n

The command is NETWORK, followed by the network\xa0\n

length. So, you can write /24 or 255.255.255.0,\xa0\n

from 192.168.1.0/24 to clients, although it\xa0\n

Then you can configure the DNS server\xa0\n

So, in this case R1 would tell PC1 to use Google’s\xa0\n

You can also configure the domain name of the\xa0\n

is part of the domain ‘jeremysitlab.com’.\xa0\n

What’s this? It’s the default gateway. So, R1 will\xa0\n

their default gateway. You can also configure the\xa0\n

5 hours, and 30 minutes. You can also enter LEASE\xa0\n

not recommended. So, when PC1 comes online\xa0\n

it will be assigned .11, the first available\xa0\n

Let’s confirm. Here’s a really useful command\xa0\n

SHOW IP DHCP BINDING. It shows all of the DHCP\xa0\n

Here’s PC1, with an IP address of 192.168.1.11.\xa0\n

lease expiration date and time, and the binding\xa0\n

but we didn’t do that in this\xa0\n

Here’s the domain name, jeremysitlab.com. Here’s\xa0\n

Here we can see when the lease was\xa0\n

Notice that the lease period is 5 hours and 30\xa0\n

times on PC1 and R1 are different, but that’s\xa0\n

And finally we can see the\xa0\n

and DNS server. So, we successfully\xa0\n

Now, how about DHCP relay agent configuration?\xa0\n

SRV1 is a DHCP server and R1 will be a\xa0\n

To configure it as a relay agent, first enter\xa0\n

to the client devices. PC1 is connected to R1’s\xa0\n

all you need is one command, IP HELPER-ADDRESS,\xa0\n

Of course, make sure R1 actually\xa0\n

If it doesn’t have a route, configure a static\xa0\n

After configuring that I checked the interface\xa0\n

‘helper address’ is listed here, 192.168.10.10,\xa0\n

to do to configure a router as a DHCP relay agent.\xa0\n

Okay, one last thing you need to be able to\xa0\n

be a DHCP client, meaning it can use DHCP to\xa0\n

This is rare, as I mentioned earlier usually\xa0\n

fixed IP address. However here’s how you\xa0\n

on its G0/1 interface. From interface config\xa0\n

That’s it, now R2 will broadcast a DHCP Discover\xa0\n

it did, I checked with SHOW IP INTERFACE G0/1.\xa0\n

Note that its G0/0 interface is still\xa0\n

Here’s a summary of the commands\xa0\n

A couple commands for the Windows command prompt,\xa0\xa0

then Cisco IOS commands to configure a DHCP\xa0\n

If you don’t remember any of these commands, go\xa0\n

practice with some of these commands in today’s\xa0\n

Before moving on to the quiz, let’s\xa0\n

First, I introduced the purpose of DHCP. It\xa0\n

configuration parameters, such as their IP\xa0\n

I introduced the basic functions of DHCP. Make\xa0\n

and Ack. You should also know the basic\xa0\n

Finally I showed you how to\xa0\n

First, how to configure a Cisco router as a DHCP\xa0\n

DHCP client. Make sure to watch until the end\xa0\n

Software’s ExSim for CCNA, the best practice exams\xa0\n

What is the correct order of messages when a\xa0\n

Here are the options. Pause the\xa0\n

The answer is B, Discover, Offer, Request, Ack.\xa0\n

remember D-O-R-A, DORA.\xa0\nOkay, let’s go to question 2.

Which of the following Windows command prompt\xa0\n

Discover message? Here are the options.\xa0\n

The answer is D, IPCONFIG /RENEW. This will\xa0\n

to get an IP address from any\xa0\n

C, IPCONFIG /RELEASE will make the\xa0\n

to release its current IP address. A and B are\xa0\n

Examine the following DHCP Offer message that\xa0\n

did SRV1 send it to? Here are the options.\xa0\n

The answer is D, 255.255.255.255. How can\xa0\n

I didn’t show the IP header? It’s here, the\xa0\n

In the previous examples, this field was unicast,\xa0\n

client. However in this case it is broadcast, so\xa0\n

Therefore, the destination IP address is\xa0\n

Which of the following DHCP messages can be sent\xa0\n

the options. Note that this includes messages\xa0\n

as well as messages that are always sent unicast.\xa0\n

The answers are A, DHCP Ack, C,\xa0\n

A and E are messages sent from\xa0\n

and they can be sent using unicast if the\xa0\n

C is sent by a DHCP client to its DHCP server, to\xa0\n

It is sent unicast. B and D are always broadcast\xa0\n

In which of the following situations would you\xa0\n

are the options. Read them carefully, and\xa0\n

Okay the answer is A, when the router is\xa0\n

in the router’s connected LAN, and there is\xa0\n

B, C, and D do not require the router to\xa0\n

for the quiz. Now let’s take a look at a bonus\xa0\n

Okay here's today's Boson ExSim practice question.\xa0\xa0

You are the administrator for the network\xa0\n

are provided by the DHCP server on NetworkB.\xa0\n

Which of the following commands should you\xa0\n

IP addresses from the DHCP server? Select the\xa0\n

IP HELPER-ADDRESS commands, so which router\xa0\n

be the IP address you enter in the command? Okay,\xa0\n

Okay let's check. So, these clients\xa0\n

or they want to be DHCP clients. So they\xa0\n

So they will broadcast DHCP Discover messages\xa0\n

a DHCP server, but we have to configure it as a\xa0\n

and F have you issuing the command on RouterA.\xa0\n

Okay, so what should be the IP address? The\xa0\n

address of the DHCP server. So that is 10.10.3.5,\xa0\n

And that is correct. So, you can\xa0\n

including some explanation about the IP\xa0\n

Okay and that's Boson's explanation, and they\xa0\n

about the IP HELPER-ADDRESS command.\xa0\xa0

Okay so that's Boson ExSim for the CCNA.\xa0\n

exams for the CCNA, and they're the\xa0\n

If you want to get Boson ExSim, follow\xa0\n

There are supplementary materials for this video.\xa0\xa0

There is a flashcard deck to use with\xa0\n

be a packet tracer practice lab so\xa0\n

That will be in the next video. Sign up for my\xa0\n

and I’ll send you all of the flashcards\xa0\n

Before finishing today’s video I want to\xa0\n

please click the ‘Join’ button under the video.\xa0\n

Marcel, Magrathea, Kone, Donald, C Mohd,\xa0\n

Benjamin, Tshepiso, Justin, Prakaash, Nasir,\xa0\n

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Sorry if I pronounced your name incorrectly,\xa0\n

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