So in our journey, we've done iCMP jitter, UDP jitter, we've done HTTP SLAs. In
this video,
I'd like to walk you through setting up an IPSLA measuring DNS. So if you want
to verify that
the DNS server is functioning correctly, we can set up an IPSLA to test that.
So for our test,
we'll use R1 again as the probing device, we'll use server 1NUG as the DNS
server,
and for the DNS request we want to make it from that server, I know on that
server I've got an entry
for PC1. So we can do a query for PC1.nuggetlab.com. And if we get a response WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
for PC1. So we can do a query for PC1.nuggetlab.com. And if we get a response
back, it is successful
for that name and it resolves it correctly, that would indicate that our IPSLA
is okay. And if we
don't get a response back from that for any reason, that would cause our IPSLA
to fail, meaning
giving us a negative result indicating it's not working as expected. So let's
head over to R1
and set up this new IPSLA. And for the IPSLA number, for jitter, we did one,
and this is two,
and this is three, so let's go ahead and use the IPSLA for DNS, and let's use WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and this is three, so let's go ahead and use the IPSLA for DNS, and let's use
IPSLA ID number four.
So here back at R1, we'll do a show IPSLA summary to remind ourselves where we
're at. So we have
three SLAs, they're all currently at this moment, they're all still running. So
let's go to configuration
mode, IPSLA, for press enter. And for this one, we want to do DNS. So we'll go
ahead and type in
DNS, or copy paste it in space question mark. And the DNS name we want to
resolve is going to be
PC dash one.nuggetlab.com space question mark. And then we're going to type in
name server and WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
name server and
specify our name server, which is down at 192.168.1. This is verified to dress
real quick in the topology.
That's at 192.168.1.100. We'll put that in as the DNS servers IP address. And
for the source IP
address, we don't have to specify a source IP address, but it'll be easier to
pick up out of the
packet capture, because other devices may be making DNS requests. So specify
also the source IP,
and we'll specify the source IP address as the loopback on our one. So type in
source dash IP,
and the loopback address of 1.1.1.1. And that's it and press enter. And then WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and the loopback address of 1.1.1.1. And that's it and press enter. And then
for the frequency,
let's go ahead and do that every 30 seconds. And we'll type in exit, so do show
run pipe
section SLA. So we can see our work, and take a look at IPSLA for which is
right here. That looks
good. However, we do a do show IP SLA summary. It is not running. And that's
because we need to
start it. So as we did previously, we'll go ahead and start it, except the time
we'll specify
the SLA idea of number four, I'm going to start it now and just tell it to run WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the SLA idea of number four, I'm going to start it now and just tell it to run
forever and press
enter. And now it should be running. So we'll do do show IP SLA summary. And it
is. All right.
So it's running, it says it's okay as far as the return code. And if we did a
command show IP SLA
statistics, and then we put the SLA number for that DNS SLA in, which is four,
and followed by the
keyword details and press enter, it gives the details on that. So number of
successes one,
which is great. And it'll continue to grow as it does probes, in our case, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
which is great. And it'll continue to grow as it does probes, in our case,
every 30 seconds. So
if we wait a few seconds here and the same command again, now we have number of
successes too.
Fantastic. And if you want to see what that look like on the back end with a
protocol analyzer,
let's take a peek at that as well. So we'll start our capture here. There's a
lot of DNS
happening. However, I think a lot of that is coming from our Windows client.
And oh, here's one from 10
dot 0 dot 12 dot one. I saw that there so I wouldn't stop that. And let's go
grab that one. So 10
dot 0 dot 12 dot one. Oh, that's OSPF. So let's go ahead and do a display
filter. And let's just WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
filter. And let's just
look for DNS. So put that in as display filter. And then here is an example
right there packet 31,
they open it up, make that a little bit bigger and scooch that down just a
little bit. So there's
our DNS request that our one was making. Here's the query looking for PC one
dot nuggetlab.com.
It says the response is in packet 32, which is the following packet. So we'll
go ahead and close
that. And let's take a look at packet 32, the response. So make that a little
bit bigger. So
here is the query. And here is the answer. If we expand that and the response, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
here is the query. And here is the answer. If we expand that and the response,
the DNS answer
to that, what is the IP address of PC one dot nuggetlab.com. It shows it as 10
dot 0 dot 1 dot 10,
which if we look at our topology happens, good news happens to be correct. That
is PC one's correct
address. So that's an example of our probe going from our one down to our DNS
server,
just to validate that service is up and running and functional. So if we go
back to our one,
and we do a show IP SLA statistics for details. Now it's had seven successes. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and we do a show IP SLA statistics for details. Now it's had seven successes.
And there's the
latest round trip time is 72 milliseconds. So another critical service that we
can measure with an
IPS, like would be other things like FTP services or DHCP. In fact, in the next
video,
let's do an example of testing and validating their DHCP services are working
and measure that
by setting up an IPS a looking for DHCP. So I'll see you in the next video for
exactly that.