- [Instructor] A key objective for the CCNA
is configuring, verifying, and troubleshooting
a DHCP server on various Cisco devices:
routers, switches, access points, whatever.
We have a switch off the Corp network, off the LAN.
Let's go ahead and make that a DHP client.
Let's configure DHP on the Corp router,
and let's then verify and troubleshoot
DHP on the Corp router.
So, let's log into the Corp router
and configure a simple DHP server,
nothing hard about this.
Step one, exclude your addresses first.
If not, you'll end up with a duplicate
as soon as you create your pool.
So notice I excluded ten addresses.
Now I'm gonna say
I'm gonna create a pool for the Corp LAN,
and I'll create one for each of my networks.
So now I have the Corp LAN,
and as soon as I add the network in here,
which is why I excluded the addresses,
you will start handing out addresses
as soon as I press enter.
So, I press enter, and it would find and understand
that 10.10.10.1 is off the f0/0
and would respond to client requests.
There are a few other things that we need.
We need to put in the default gateway for the users,
for the clients,
and at a minimum, we might do more than this,
and we will in another section,
the DNS server.
Very simple, to the point, exclude,
create your pool name, add your network,
default gateway, DNS server, that's your minimum.
So let's run out to the switch and take a look here.
This is the switch connected off of the f0/0 interface.
And to configure a switch,
we haven't covered this yet, and that's fine,
I go under a logical interface and say ip address dhcp.
This'll be covered in detail in another section.
Right now we do not put an IP address under-
I have to enable the interface-
under a physical interface.
You must put it under a logical interface.
So, the interface came up.
Syslog is showing me that it's up,
and I got a DHP address 'cause I'm directly connected.
It doesn't get much simpler than this, guys.
So we'll complicate things in a minute.
So let's go back to the corporate router
and do some verification here.
So, it's got an address,
so show ip dhcp is your friend here.
You must understand this.
So, we'll do binding, conflict, pool, and server.
And this showing me that I have a 10.10.10.11 out there.
Why did I give it 11?
Well, remember that's the first one in the range.
We had reserved one through ten.
And take a look at conflict.
Let's see if conflict, I had any conflicts.
Now, I don't have any conflicts.
If I had a conflict, it would show up here.
There's two different types.
Let's talk about this.
There is something called a gratuitous arp.
If a client receives an IP address
from a DHP server, it's going to send out
an arp request that says,
using the IP address that it received,
"Hey, anyone out there know the Mac address
for this IP address?"
If someone responds, they go,
"Uh oh," and they tell the server there's a conflict.
So you'll see the detection method as gratuitous arp.
The other thing is before a server sends
an address from the pool,
it's going to ping that address
and see if someone responds.
So, and if that's the case they'll show up here.
We can also then do ip dhcp pool,
and we'll see how many addresses are leased,
and then the last one is server statistics.
And this is going to show me my memory usage,
address pools, and so on on this.
We've done it very simply, but one last thing
I want to show you is look at the bottom.
We've talked about this already, the DORA:
discover, offer, request, acknowledgement.
And we can see the sent and received on this.
Okay, so that's very cool.
So you can see this occur here.