Lesson: 13.6 Lab Observe DNS and DHCP (CCNA 1: Introduction to Networks Semester 1 of 3)

hello and thank you for watching the sixth lesson of chapter 13 which is 13.6 it's our lab observe dns and dhcp now chapter 13 theory is done completed well it wasn't all theory we did law practical work we looked at the wireshark the tcp http dns dhcp and as well as ftp packets on the wireshark so you should be a lot more comfortable on how to use wireshark as a program for that reason everything i'll do in this lesson in this lab i'm going to use a packet tracer so everything will be from scratch so you'll get to see all these packets on the packet tracer as well right so what we're going to do in this lesson or in this lab we're going to see well we're going to access a website from the pca that that website will be hosted on server b and we'll observe the communication we'll see the dns packets we see the tcp packets as well as http packets so this is the lab topology that we will be building from scratch so we will get a router and we'll say router one and then that router will be the dhcp server as well and we'll bring a pc that will be a dhcp client and it will get an ip address from the router and we'll bring couple of servers server a there will be a dns server with this ip address and then server b that will be our web server with this ip address and the idea is that we get access we open a web browser from pca and we try to access a website called cisco.local which will be hosted on the server b now the pc is going to send a dns query to server a for that website and the server a as a dns it will send a dns a query response to that query and then once we get response you'll see that the pc will start the tcp three-way handshake so we'll get the three-way handshake going so the first message is going to be the synchronization message from this pc towards the server then the server a web server will send us acknowledgement so we'll acknowledge that synchronization as well as their own synchronization message and then the third handshake will be ack from this client which will say okay i'll i'll acknowledge your synchronization and then we just after that the client will start sending the http packets right that's the idea okay so i've already have a packet tracer so i'm just going to bring it in here here we go that's our packet tracer so i'll grab a router 1941 router i'll need a switch so i'll put 2960 switch and i'll put an end device which is going to be my pc and couple of servers now i'm going to change the name here for visual help or effect here so that's not different so pca and if you just click on the name you can change the name here but that doesn't change anything it's just going to help us to know what the devices we already have we have in our network okay and then i'm going to connect them yes so everything is straight through connection because all are dissimilar devices so switch g01 to router g01 and then i'll connect switch i'll connect to the pc it doesn't really matter what port on the switch it will matter when we talk about vlans and spanning tree later on but for the moment it doesn't really matter i'm just connecting them to any port i have okay so this is going to be the server a it's going to be my dns server and the ip address is going to be 192.168.1.20. this is going to be here the server b it's going to be the web server so web server and the ip address is going to be for the website let's put the website cisco.local local and uh ip address 192.168.1.30 30. and the router is not really in this that's not going to be that much it's just going to be our dns sorry dhcp okay that's it and this is the pca it's going to be the dhcp client yeah so i'm not going to write that down so on the router i'm going to copy i've got already some notes well commands that i'm going to copy to the router and these are just normal default commands that we've gone through so many times and uh i've got the configuration for the interface g01 and i've got the dhcp configuration now dscp we're going to cover it in the next semester so we just don't worry about these commands at the moment but what i'm just saying that i've excluded some addresses from 1 to 150 i have excluded so the the pc should actually get 151 as an ip address it doesn't matter let's let's exclude something else here one two five let's say one two five now all the ip addresses from one to one to five are excluded so the pc should get actually one two six so i'm going to copy all this configuration to my router right so copy go to the router and just paste it there right look have a look if there is any errors which there is not okay so the router is done the next let me just minimize this as well we don't need it so i'll go to the pc and then on the pc i'm going to configure the for example the ip address to get it dynamically but i'm just waiting for this to go green because of the spanning trees so it's about 50 seconds so might as well just do server a so i'll go to server a go to desktop ipconfiguration this is going to be a static configuration so 192.168.1.2 default subnet mask the gateway is going to be the router 1 and dns server is going to be itself so 127.0.0.1 right now server b now server b if i go to desktop here of the server b the ip address statically 192.168.1.30 default subnet mask gateway 192.168.1.1 and then this dns server is going to be 192.168.1.20 which is the server a okay this is done now if i go to pca you see the router has given the dns as well yes so dns192168 so it says that one so if i go to pca go to ipconfiguration dhcp now you see we got 126 the address so let me just mark these 192.168.1.126 has got the address here the gateway is r1 but the dns server is dot 1.20 is this one here right so we are almost done ready so what are we going to do i'm going to go to simulation i don't want to see all these packets well i want to say show none and i want to see only dns packets and i want to see http packets and tcp packets those are the three packets i want to see dns http and tcp what's going to happen dns request dns response then three-way handshake first two three let's see all the tcps and then the last bracket is going to be http well the next packets okay that's the idea right so minimize this zoom in a little bit so we can see it better and that's it we go to the pca close this or before i do that let's configure the dns server now the web server we don't have to configure because if you go to services http is enabled by default so we don't have to worry there at all but the dns is not so i need to go to this server a and access the dns and enable that before first and then say okay if anybody wants to go to cisco.local point them a record right to this address 192 168.1.30 which is server b address i'll add that information okay we are ready so i'll go to pca open the web browser which is right at the end here last uh top whatever the the last tab web browser and in there i'm going to type cisco.local so cisco dot local and press enter now i'm going to just see here the first packet is going to be the dns packet as you can see type dns if you click on that packet for example to inspect it look at outbound pdu and this is you have a ip header then you have a udp header which is port 53 here and then we have a name which we're trying to resolve is cisco.local and this dns package should go to our dns server so if i move it forward it's going to go towards the dns server there we go and the dns server is going to if if we inspect it on dns server we see the inbound pdu sorry okay inbound pdu i don't know what was happening there so inbound pdu is cisco.local and outbound is like what i'm going to send to them what i'm going to send to them is the ip address 192.168.1.30 that's the outbound that's outgoing so if i click forward that's going to go towards the pc and now the pc is going to create the tcp three-way handshake so this packet is tcp so as you can see the tcp is the first handshake so if i click to inspect it so outbound i've looked on iptcp you can see the destination port 80 source port sequence number acknowledged number windows but i want you to pay attention to this bit here the not the last one the zero the one this one here that bit says synchronization bit that's my synchronization is being set yeah so synchronization is set and let me close this and that's gonna go towards the server now and when it gets to the server we can inspect it there so the server says okay in inbound i have synchronization someone wants to talk to me outbound i will acknowledge that that's the acknowledgement the next one there that's the acknowledgement if i can just point it so small and then they have their own synchronization that's the second handshake coming from the server yeah so that's going to go back to the pc and once the pc gets that it's going to create this is http packet but as well as it's going to send one tcp packet so if i forward it that packet is a tcp if i look at that packet once it gets to the server you see that packet when i go inbound it got to the end that's acknowledgment that's is that's a three-way handshake it's done and the next packet is going to be your h normal http package so if you look at the http packet in the inbound inbound we'll say okay well i need to i need information about cisco.local and outbound the well we're going gonna send that information all the the html webpage right so once i get there to the pc then we look at the pc we should see that's acknowledgement coming and then there we go we see the webpage okay so what happened if i go back very quickly that's where we started that's your dns lookup or like query towards the server the server sends a response towards the pc gives the ip address of the web server then we start a three-way handshake that's your first tcp handshake synchronization then the thing acknowledgement and synchronization comes from the server then the third handshake is well acknowledgement from the pc that's why it's green and as well as we send the http get message once we send the gate get message the server replies with the contents of the website and then we look to the pc we have the packet tracer before that it wasn't it wasn't uh we don't have the website okay that's it so we saw the three packets we saw the dns we saw the tcp packet and we saw the http packet thank you for watching lesson 13.6 lab observing dns and dhcp this is of chapter 13 application layer please have a look at my other videos and don't forget to subscribe to my youtube channel to stay up to date this has been asriel krasnichi bye

Channel: Astrit Krasniqi

Views: 387

Keywords: Application Layer, Presentation Layer, Session Layer, Client-server model, Peer-to-peer, Uniform Resource Locator (URL), Uniform Resource Identifiers (URI), HTTP/HTTPS, GET, POST, PUT, SMTP, POP, IMAP, Domain Name Service (DNS), Fully-Qualified Domain Names (FQDNs), nslookup, Dynamic Host Configuration Protocol (DHCP), DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK, File Transfer Protocol (FTP), Server Message Block (SMB)

Id: ILNvlZedRak

Length: 13min 47sec (827 seconds)

Published: Fri Oct 30 2020