DHCP is a really important feature
for most of our networks.
And if it's not available, that's a problem,
and we want to know about it.
And one way we can track that is by using an SLA,
looking for whether or not the DHCP server is
able to hand out IP addresses.
The way this works is, the SLA, based
on the frequency we specify, acts as a DHCP client
and wants to lease an IP address.
And then, once it gets, it releases it,
lets the DHCP server have it back,
and then it waits until the next cycle,
and then does it again, if that SLA is running. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and then does it again, if that SLA is running.
So in this video, we get to create a DHCP server
on a router.
We'll set up an SLA that's checking on a DHCP server,
and then we can monitor it, see whether it's up or down,
based on the SLA.
So let's take a look at the topology
and then we'll go to the lab.
And here's what I propose that we do in this hands on lab.
Let's create-- on R5, we'll create a DHCP server.
And it doesn't have to be fancy, we don't need lots of options.
In fact, we can just create a pool and say, for that pool,
it's going to be 10.1.57.0 with a 24-bit mask. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
it's going to be 10.1.57.0 with a 24-bit mask.
And that'll be enough.
A pool with the network in it, and that'll be good to go.
Then we can set up an SLA in R7 that's
checking to see whether or not that DHCP
pool, or that service, is available by simply trying
to get an IP address, get's it, releases it, and then waits
again.
So we're going to do all that configuration right now.
I will walk you through it, step by step.
If you're sitting at a computer, logged on to the CBT Nuggets
website, click on the virtual link,
get the hands on practice to help reinforce these concepts. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
get the hands on practice to help reinforce these concepts.
Let's go to the CLI on R5 and set up our DHCP server.
All right, let's go to R5, let's do a show.
IP pools-- not polls.
Do you like DHCP servers?
I do!
Poll is in.
Pool, all right.
OK, no pools, let's create one.
So config t, IP, DHCP pool, and we'll
call it our pool, because it's our pool we're going to create.
And then we'll put a network, and 10.1.-- WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And then we'll put a network, and 10.1.--
let me verify where we are.
Do a do show IP interface, let's do
a do show IP route, connected, that'll be good.
Let me see directly where we're connected to.
So let's make it for the 10.1.57 network.
So actually, I could just copy that, little cheat there.
And we'll say network, and we'll paste in that network,
and I'll just add a little space there, boom.
Now, that's it.
And we could-- so all the other options, and default gateway, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we could-- so all the other options, and default gateway,
and DNS, and exclude addresses, we
don't really need that for this demonstration.
We'll do a show IP DHCP bindings, and nothing there.
Let's go to R7 and create an SLA, syntax very similar
to all the SLAs.
In configuration mode, IP SLA, and then give it a number.
So what is the UDP port numbers for DHCP,
I think it's 67 for the server and 68 for the client.
There we go.
So we'll use that number, just for fun.
That's the ports involved. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
That's the ports involved.
And press Enter, and then it says, great,
what do you want in this SLA?
And what we want is DHCP, then we'll do a DHCP.
And then the host is going to be--
what is the host?
Go to R5 real quick and take a look.
And the address is going to be 10.1.57.5, right there.
We'll go back to R7, that's the IP address of our server.
And I'm not going to specify a source address,
I'm not going to worry about option 82. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
I'm not going to worry about option 82.
And all right, so now it's a DHCP SLA.
How often do we want to run, frequency,
how about every five seconds.
That's a lot.
We really don't need one every five seconds,
but you can set that to something more reasonable.
But I didn't want have to wait, I
want to be able to see it in action.
And enter now.
Oh, it has to be at least 10 seconds.
All right, 10 seconds it is.
And now that we have this SLA, we need to schedule it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And now that we have this SLA, we need to schedule it.
So it's IP, SLA schedule, and the number is 67, 68.
I'm going to scroll up a little bit
and check that, fair enough, 67, 68.
Let me make sure I have the the right number.
And I'll go and say, start time after.
And let's go ahead and do zero hours, zero 1 minutes,
and 0 seconds, great. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and 0 seconds, great.
And then once it starts, we want the lifetime
to be 10,000 seconds, great.
So in about a minute, it's going to run.
Well, not an hour, a minute, yep.
So if we do a show IP SLA statistics, all right,
here it is, operation code is unknown.
Because it hasn't tried it yet.
If we do a show IP SLA, what are some of the good ones?
I would encourage you in the lab to play with these as well.
The show IP SLA application will show you WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
The show IP SLA application will show you
what the actual features are, right here.
So all these features are available.
And here, it's showing us that we
have one SLA configured and one pending, all right.
So this also would show us, once we
have them configured and running,
it would show us that one is running as well.
OK, I guess we just wait for a minute.
Show IP SLA statistics, and no successes,
no failures yet, because it hasn't quite started yet. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
no failures yet, because it hasn't quite started yet.
But we can do the application command.
Oh, wait!
Yeah, check it out, it's now active.
Doo, doo, doo, doo, doo, doo, it's running.
So now, if we did a show IP SLA statistics,
look at that, one success.
And I think we set it to every 10 seconds,
so it's going be doing it every 10 seconds.
If we go back to R5, and we do a show IP DHP binding,
look at that, we caught it!
So it's in there.
And what should happen, it should release it
after a few seconds. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
after a few seconds.
There we go, it's not in there.
So what's happening, so the SLA is going in, asking for an IP
address, getting an IP address, SLA comes back all happy,
and then it doesn't release, and gives it back to the router.
Oh, look at this, it's going in.
So the DHCP server is like, OK, the 3, and then 4,
and then 5, it's giving them out in order.
Oh, look, address conflict at 7!
[CLAPS] I love it!
So we do a show IP DHCP conflict. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we do a show IP DHCP conflict.
And that's because R7 has the address of dot 7.
Oh, and dot 5 belongs to R5, that's
why I didn't hand that one out.
All right, that's so great, so great.
All right, anyway, if we hit show IP DHCP binding,
it would just keep going up and up.
If we go back to R7, where the SLA is,
we could then take a look at the statistics.
And these successes keep going up.
So every time, every time this router
asks for an IP address via the SLA, it got it.
And that conflict is when R5 said, yeah, there's WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And that conflict is when R5 said, yeah, there's
a conflict, not that one, and it skipped it,
went to the next one.
OK, so in the next video, I'd like
to share with you something really important, that's this.
Besides the SLAs tracking the service,
and tracking the latency, and tracking whether or not
there's connectivity across the network,
we can also tie an SLA with the option of tracking.
So that if we have a static route, for example,
we can say, this static route, it's
only good if this tracked SLA is up and working.
So if the SLA says, no, this isn't
working, that static route can be WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
working, that static route can be
dropped from the routing table.
Or we can have HSRP as another example of many.
With HSRP saying, OK, this is the primary, the active router,
and I'm forwarding, forwarding, forwarding,
but I'm tracking based on a SLA.
And if that SLA is no longer successful,
the tracking object goes down.
Then the router could say, OK, I'm
decrimenting your priority by 5 or by 10
on that HSRP active device.
And if it goes low enough, and the other one
is set for preempt, the standby router WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
is set for preempt, the standby router
can then take the active role and start forwarding,
based on a connectivity failure somewhere in the path of what
was the active shooter.
All right, so in the next video, what we'll do
is, in hands on lab, what we'll do is, we'll set up another SLA
and we'll include it as part of tracking.
So we can influence the network behavior,
based on an SLA having success or failure with its probes.
All right, so I'll see you in that next video
in just a moment.
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.