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ROUTING AND SWITCHING ESSENTIALS

12. DHCP

We're going to talk about the DHCP protocol in this section, so let's start with DHCP version 4. First, DHCP is a client-server protocol that automatically provides an IP host with its IP address and other related configuration information, such as a subnet mask and the default gateway or the DNS or something like that. DHCP uses port number 67, and for example, if you are managing a network with 1000 clients, it is almost impossible to assign IP address configuration manually for each client. So DHCP is almost mandatory for big corporate networks. The DHCP process goes through four states while assigning an IP address to the client.

These states are often abbreviated as "discover," "offer," "request," and "acknowledgement." In the discovery stage, the client sends a broadcast message on the network, as you can see here, and searches for an active DHCP server. When a DHCP server receives the DHCP Discover message from a client, which is an IP address list request, the server receives an IP address for the client and makes a list offer by sending DHCP offer messages to clients. In response to the DHCP offer, the client replies with a DHCP request broadcast to the server, requesting the offered IP address. When the DHCP server receives the DHCPrequest message from the client, the configuration process enters the final stage. The acknowledgement stage involves sending a DHCP actpacket to the client, and this actpacket includes the list duration and any other configuration information that the client might have requested. Dynamic Host Configuration The DHCP protocol is a server protocol for assigning a dynamic IP address to the computer.

A DHCP server enables computers to request IP addresses and networking permissions, automatically reducing the need for a network administrator or a user. If we configure these settings manually, we can also use our routers as DHCP servers, and here is the configuration to configure a router as a DHCP server. First, we need to define an IP pool by typing "IP DHCP pool" and the name of the pool, which is "my pool" for this example. Okay, then we are getting into DHCP configuration models, as you can see, and we are typing the address range. To begin, we will define the network command and network ID with a subnet mask for this address range. Okay? which means our range will be between 10 (411-0224.Okay, I'm going to start from one and go until two, 5200, and four.

OK, then we're defining a default router, which is the default gateway, and the default gateway of this network will be this router's 1041 interface. Okay, then we are defining a DNS server, and our DNS server will be this. Then we are also defining a domain name, which is networkyl.com. Okay, what I'm doing in here is also, as you can see in the last command, defining something more. Ipdhcp excluded address 11215, which means I'm excluding this range. OK, I want to use this range. That means the address range for PC One will be from 1 to 6, because PC One is our default gateway and won't be used. And I'm also excluded from this range, which includes my default gateway too. Because of this, the address range that PC One can use will be this range. To check a router's DHCP server options, use the show run section DHCP show IP DHCP Binding and Server Statistics commands. If you want to assign a dynamic IP address to a router's interface, you can use the ip address and DHCP command under the related interface mode. This is not something that we usually use, but you may face these questions in your exam.

So in here we are getting into the interface mode by typing interface gig zero zero, which is here, and by typing the iPad DHCP command. Rather, gig interface gathers an IP address from the DHCP server dynamically. The most common use of a router for DHCP services is the DHCP relay. DHCP relay is the router that forwards DHCP broadcast packets to the DHCP server, which is also known as the "helper." For example, if PC One makes a DHCP request, one will forward these packets to the valid TCP server, which is 10 41 25. For this example, let's go ahead. DHCP version six IP version six prides itself on being a protocol that supports many dynamic plug-and-play functionalities. As a result, there are multiple ways to assign IP addresses in IP version six. To configure IP version six host globalUnique globally, we have two options, and they are Slack and DHCP version six. In the Slack option, Rather can send IP address, prefix length, and default gateway information to the clients. In the DHCP version six option, the DHCP server sends IP address, prefix length, default gateway, DNS server, and domain name information to clients similar to IP version four.

Let's start with the slack in slackoption: a router can provide three types of information to configure dynamic IP addresses. The first is slack only. In this option, Router offers to use the information that Rather sends only in the second option, which is Slack and DHCP version six. In this option, the router offers to use the information it sends and offers to receive the rest of the options from the DHCP version six server. For example, DNS or something like that. In the third option, Rather offers to use just the HTTP version 6 server. Okay, this is how Slack actually works: the host makes a request first, which is a rather solid station message, and says, "Hey Rodder, I need IP version six options." Okay, our IP version six router gets this request and can reply in three ways. The first reply is Slack only, which includes your IP prefix length and the gateway replying to the host. The second option is Slack and DHCP version 6, which includes your IP prefix length but asks the DHCP version 6 server for DNS and domain names. Here, we are defining something. We are providing some of the information from the router, and we are defining some of the other information from the HCP version six.

And the last message can be DHCP version six, which means I'm sorry, my friend; ask for HCP version six. In IP version six networks, which are too similar to IP version four in this configuration, we can use our router as a DHCP server; instead, one offers a DNS server and domain name. As you can see, First, we are defining a pool again by typing IP version 6, DHCP pool, and the name of the pool. And we've already defined the DNS for the domain name. Okay, and in here we also have another configuration IP version six and the other config flag. This flag is required because it will notify clients via a rather promotional message that they must use DHCP version six to receive additional information. For version 6, we can also use our router as a DHCP server. And the DHCP broadcast broadcast packets are forwarded to the DHCP server by this router. And here's how to set up the DHCP relay in IPV6 networks. We're back in interface mode, and this time the command is IP version six DHCP relay destination and the IP address of the removed DHCP server.

13. NAT

In our next section, we are going to talk about net network address translation, so let's go ahead with the net overview. Network address translation is the process of remapping one IP address space into another by modifying the network address information in IP detagram packet headers as they travel through a traffic routing device.

A net's primary function is to limit. The number of public IP addresses an organisation or company must use for both economic and security purposes So, why do we require a net? Because IPV4 address space is limited, each device cannot use a global address, and the private IPV4 address range is not routed by Internet routers, so they need to be translated to global addresses. Let's go ahead with the private IP address range. A private IP address is an IP address that is reserved for internal use behind a router or other Nut device. Apart from the public Private IP addresses are in contrast to public IP addresses, which are public and cannot be used within a home or business network. Sometimes a private IP address is also referred to as a local IP address. Okay, we have class ABC IP addresses, as you can see, and these ranges are the private IP address ranges that we can use in our local area network. Let's go ahead with the net terminology.

In net terminology, we have terms such as "inside global." For example, I'm sorry, "inside local," which means your host IP. For example, if you are on PC 1, your inside-local IP is the IP address of PC 1. Let's go ahead with the inside global. "Inside global address" means your public IP address in this statement. In this example, our IP address inside iTunes is converted to this public IP address. So that means our inside global IP address is this. And we have the "outside local IP address term," which means remote host IP. Here, the remote host is this, our outside local IP is this, and the outside global IP address is the remote public IP address, which is this IP address. For this example, let's go ahead with the nuttypes.

There are three types of network address translation: static, dynamic, and port address translation (PAT). In the static net method, private addresses are matched with global addresses. For example, if PC One will go ahead and connect to the Internet, that's going to use this IP address; if PC Two will connect to the Internet, that's going to use this IP address; and PC Three will use this IP address. In Dynamic Nutmeted, a public IPV4 pool is configured on a router, and IP addresses are assigned with the "first come, first served" rule. For example, if this guy wants to serve on the Internet, he'll get this IP address from this pool. If, secondly, PC Three wants to surf the Internet, this guy will get this IP address. And if PC Two wishes to serve to that, it will use this IP address. Let's go ahead with the port address. Translation: in the Pub method, each private address is translated to a single or failed public IPV. Four address and port addresses are used for choosing the right internal device when the packet is coming back.

In this method, we have PCs 1, 2, and 3, as you know, and all of these guys have the private IP addresses of this, this, and this for each PC. And we just have one public IP address and our private IP addresses; all of them are being converted to a single IP address in part method. Let's go ahead with the nut configuration. To configure a static nut, we are typing "Ipnotinside source static" and our private and public IP addresses that we want to convert. Then we enter the interface mode of our router. And for gig zero, which looks to the inside, we type IPnet inside command and Ipnot outside command for gig one, which looks to the outside. To verify the static router configuration, we can use the show IP Nat translations command and check the inside local and global IP addresses. Let's go ahead with the dynamic Nat configuration. So we need to first define an IP address pool here. To define a pool, I'm typing IPnet pool, the pool's name, which is network YL, and I'm defining the range of the pool with the name mask keyword, and I'm typing the subnetmask that I'm going to use for the pool. Then I'm creating an access list, and I'm permitting my internal network, which begins with 1041 here, and I'm using the proper wildcard mask. In the third step, I type IPNet Insight Source List, the access list number, and our pool name.

Then in the last step, I'm getting into the interfaces gig and gig one, and I'm typing the IP not inside and IP not outside statements. Here's the configuration of the pad: For pad configuration, we are using similar logic with the dynamic net. We are creating a pool again with an IP netpool name network, and we are defining the IP address range, which are the same ones because I'm just going to use one IP address with this subnet mask. Then I'm creating an IP address again, which is defining my local network.

Okay, the IP addresses that I'm using are just starting with 1041, and this access list hits these first three bits, and here's the statement starting with 1041 one.Okay, now I'm going to type IPNI inside-source list ACL number pull my poolname, and I'm going to use an overload keyword. Okay, that's the key difference. Then I'm getting into the interface modes, and I'm typing IP nut inside and outside statements again. So let's take a look at the nut for IP version six. Lastly, IP version six has a huge address space, so there is no need. not for private or public translation. Nut is only used for communication between IPV-4 and IPV-6 devices, and this method is known as "net 64."

14. Device Discovery & Management & Maintenance

In this section, we are going to talk about U.S. discovery, management, and maintenance. We'll start with CDP and LDP. CDP is a Cisco group router protocol used to share information about directly connected Scot devices. This is an OSI Layer 2 function. If you want to enable it globally, you can use the CDPenabled command, and if you want to enable it per interface, you can use the CDPenabled commands under the related interface.

But CDP is active by default on most iOS versions. OK, in here we have just two routers connected directly to each other, and if I type, for example, the Show CDP Neighbors comment on RouterOne, I will see the information related to RouterTwo, such as its model and the interfaces connected to this guy to verify the CDP. As I told you, I'm using the show CDP neighbours command, for example, in Router 1. If I type the Show CDP Neighbors command, I see the device ID as Router 2, which is the host name of the remote device. And I'm seeing that the local interface that I'm using when I'm connecting to Router Two is the gig. And I can also see that I'm connected to the gigabit port of the other two.

And I can see that this device is capable of R, indicating that the router is capable; I can also see the device's module, which is the Cisco 2900 router. We can also use the Showcdp Neighbors Detail command for verification, and we can see the IP address, the platform, the capability port ID, and the version information being the same. Let's go ahead with the LDP link layer. The discovery protocol is used to share information about other directly connected devices, and that is an industry standard. Actually, that's the same thing with CDP, but that's the industry standard. Let's go ahead with the NTP network time protocol. NTP is the protocol used for clock synchronisation between network devices over packet switching, where I believe latency networks are within the NTP server and usesport number 123 over UDP.

NTP uses a hierarchical, semi-layered system of time sources, and each level of this hierarchy is termed a "strategy." Stratum zero consists of high-precision timekeeping devices such as atomic clocks and GPS clocks, and Stretch is directly connected to them. Zero, as you can see, and other layers are connected through a network, and they get their club from the upper layer to configure the NCP. We have just one command, and our command is "NTP server," along with the IP address of our NTP server, which is this IP address for this example. And we can use the Show NTPstatus and Show Entity associations for verification. Let's go ahead with the password recovery process. Password recovery is used to reset enable secret passwords, and there are different procedures for switches and routers to reset the enable secret password. You must have physical access to the device to complete this recovery process. And this process cannot be done remotely via telnet or SSH.

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