DHCP Services on a Router for the Cisco CCNA - Part 1

okay let's set up DHCP service on a router so we're going to grab a router here alright then we grab a client computer PC then we're just going to connect the two together using a crossover cable Ethernet two Ethernet that's all we're going to do a set of DHCP in this lesson we're going to go to the client and make sure the client is configured for DHCP so we go here set that and that should set it requesting DHCP so now we've got the client set up requesting IP addresses through DHCP now we got to set up the router so we'll go to the router command line interface no enter okay there's the exec prompt we're going to type in able to get to privileged exec prompt we don't have any passwords on the router this is all we're going to do is DHCP configure terminal to get to global config mode and then when we're in global config mode we need to configure our Ethernet interface right here this interface right here needs to be configured that we just connected our crossover cable to so we're going to say int which is short for interface FA which is short for fastethernet 0/0 that puts us into interface configuration mode notice we were in global config mode now we're in interface configuration mode and we're going to type IP address 192.168.1.1 space 255.255.255.0 for the interface hit enter that's good and then no shutdown right we put in the word no space shutdown or no shut for short to turn on the interface so now the interface is active now if we look down here you'll see that I've got green lights here on our interface so now we're going to do this we'll do a control C hit enter that's back to privileged exec mode then I'm going to do a comp T which is short for configure terminal like that right you can just do compte back to global configuration mode and it's time to configure DHCP for the router by the way DHCP on the router is enabled by default so it's working right now if you wanted to shut it down you would type no service DHCP and that would shut it down now for some reason it's not taking that command and I guess maybe on this router won't allow you to shut it down but that's what I've read on how you would shut it down right no service DHCP and then to turn it back on you would say service DHCP but for some reason it's not taking those commands but anyway it's on by default so all we have to do is configure it so what I'm going to do is I'll say IP first of all I'm going to set up IP dhcp excluded addresses so address is that it's not going to use to create four addresses that it's not going to hand out so IP addresses that are going to be excluded and we'll say excluded exclude 192.168.1.1 which happens to be our router interface to 192.168.1.2 nine let me open this up so you can see it alright so there you go there's the IP dhcp excluded addresses 1 9 2 1 6 8 1.1 space 1 9 2 1 6 8 1.99 all right and I put it s in here so I'm going to get rid of that just it's not addresses its address ok there we go and now we're going to create our DHCP pool of addresses that we're going to hand out so we'll say IP dhcp pool and then we'll type in my pool one right so there's my pool of addresses is going to be called my pool one the network will be 192.168.1.0 and then I'll put in the subnet mask and then now I can hand out the gateway and also the DNS server so I'm going to say default - router the default gateway will be 192.168.1.1 that sets it up and then if you wanted to you could also say what's going to be the DNS server so you could say DNS DNS server DNS - server so you're going to type in DNS - server and let's say I was the DNS server also which I'm not I could put in let's say the same address for DNS server or I could say get your DNS services from some other address right like that okay so now it's configured and it's good to go so now if we go to our client and we go to IP configuration you can see he's already picked up an IP address see requesting an IP address he picked up 1.1 hundred he's got he needs to get his default gateway though so let's see if we can put in some commands here for the client I'll do an IP config release right now he's got all zeros and then just do a renew and you can see now that it's picked up the IP address subnet mask the default gateway and the DNS server from the router another useful thing that you can do with packet tracer is analyze the process of DHCP the discover the offer the request and the acknowledge phases of the DHCP packets the handshakes essentially that set up DHCP so what you could do is is just slide this over click on this tab right here to go in simulation mode click Auto capture right then go to your client right and put in a release right and then put in a renew right and then what you could do is as that's happening you can then click on these packets to take a look at them right so you just click on the packet bring it over here and you can see what's happening in the packet you can look at the details of the packet source IP address is 0 destination is 255 you see that he's broadcasting the request right for a discovery packet is a broadcast right source port 68 destination port 67 so you can see what ports DHCP is functioning on and you can analyze that whole situation you can also see that the MAC address is a broadcast MAC address right broadcast IP address and so you can analyze all those packets and that's really useful for taking a look at what happens here

Channel: danscourses

Views: 139,673

Keywords: DHCP, router, Cisco, CCNA

Id: dtzOPWtU75w

Length: 8min 36sec (516 seconds)

Published: Tue May 03 2011