[MUSIC PLAYING]
So let's jump in and begin here with trouble ticket.
1 specifically.
And something to keep in mind as we
go through these different tickets in this skill, most
of them are going to be based off of OSPF Topology 3.
Now, there is one ticket coming up that is going to be IPv6
So that is going to be based on a different topology.
But just keep an eye right here on each of our tickets--
will reference which topology it's using.
So let's take a look at what this ticket actually says.
So this ticket says that the OSPF neighborship between R6
and R10 is currently down.
So what it's talking about is, of course, this neighborship
up here, which is going to be in area 200 between router 6,
and router 10.
So let's go ahead and jump in and take a look at this.
We'll start off by verifying that this is actually not
working.
So let's start off on the command line on router 10.
So again, we'll verify that it's actually not working.
So let's start with a show IP OSPF neighbors.
We see that, in fact, it does not
have any neighbors because router 6 would
be router 10's only neighbor.
Next, let's verify our interfaces.
So let's just do a show IP OSPF interface brief.
What we see here is that, particularly, our gigabit 1
interface is in fact, configured for OSPF.
It's in area 200.
It has the appropriate IP address and mask.
And it is a point to point link.
We also see that it has no neighbors.
But we, sort of, already knew that.
So let's verify these same things on router 6.
So we'll do our show IP OSPF neighbors.
And router 6, of course, has other neighbors
but it does not have a neighborship with router 10.
We do our show IP OSPF interface brief.
What we're looking for here is, specifically, the gigabit 2
interface.
We see that is also configured in area 200, which
it should be.
It has the correct IP address and mask on it.
And it is also configured for point to point.
It, of course, also has no neighbors, which, again,
we've already seen.
So at first glance, everything appears to be OK.
Let's take a look at a little bit more detail
on this interface since we're not
getting any information off of the brief version
of the command.
So we simply take off brief and we'll put in gigabit 2.
Now, as we look over this, there's
obviously a lot of information that's available here.
But some of the big things that can affect a neighborship,
that we want to compare two the other side, first,
would be the Hello and the Dead intervals because the timers do
need to match.
We see that this particular side is
set to 250 with a Dead interval of 1 and also, authentication.
We see here at the bottom that this is doing
cryptographic authentication.
It is currently using key 1 using HMAC-SHAK-512.
The key is OSPF key.
The key chain name itself doesn't necessarily
matter but it does have to be configured the same.
Now, authentication could definitely be an issue here.
But let's go to the other side and take a look
at its detailed information on its interface
to see if anything jumps out.
So once again, on this side, we'll look at gigabit 1.
Let's verify those timers.
We see here that they're set to 250 for the Hello.
And one second for the Dead.
So that's good.
If we look down here at the bottom,
we see that it's doing authentication
and it's using the same type.
Now again, we haven't actually verified key 1
but it is at least configured for authentication.
It is still a possibility that the key is wrong.
However, a more important thing to look at here
is we have this little statement that says, No Hellos.
Passive Interface.
Here's the thing, if we're not sending
hello's out an interface, then there's
no way to form a neighborship.
So this is definitely a problem.
Let's take a look at why it's set that way.
Let's do a show IP OSPF.
And if you look over this output,
this doesn't really tell us a whole lot
because this output for this command
is really more about the OSPF process and the OSPF areas
here at the bottom.
But passive is not an area thing or it's not a global process
thing.
Although, that is where it's configured.
This is more of an interface thing.
So let's try instead, show IP protocol.
If we look at the output of the show IP protocol,
specifically for OSPF 1, we're going to see here
exactly what we're looking for.
We see that routing on interfaces
is configured explicitly in area 200 Loopback0 and gigabit 1.
But look at our passive interfaces.
Passive interfaces includes gigabit 1.
It includes a lot of other interfaces as well.
But of course, gigabit 1 is our primary concern right now.
Well, why is it set that way?
Let's do a show run.
And we'll look at the section for OSPF.
Now, there's a lot going on here because we're also running
OSPF version 3 this router.
But if we look down here, all the way at the bottom,
we see that passive interface is set to default.
That means that it's going to do passive interface on all
of its interfaces.
In some situations, that might be
OK if we have a lot of interfaces
that we want to be passive.
But we have to make sure that we then turn off the passive
interface on the one that actually needs to send hello's.
Now, that's actually really easy to do.
All we have to do is go into the router OSPF process and say,
no passive interface.
And then you simply put in the interface
that you want to make non passive.
In our case, it's gigabit 1.
Can exit out of configuration.
Just as a note--
alternative fixes here-- we could have just taken
out the passive interface default.
So again, sort of, two fixes here.
Either take out the passive interface default,
which would then, of course, send hello's on all
the interfaces or just take off passive on the one interface
where we do need to send hello's by simply doing the no pass
and then listing the interface.
In our case, gigabit 1.
Let's see if our neighborship is up now.
And what we see is we now have a neighborship with router
6 over, not only the gigabit 1 interface.
But notice that our virtual link interface has also
come up here.
This is because a virtual link is
needed between router 6 and router 10
to connect that area 0 up at the top of router 10
to the rest of the area 0 down below router 6.
So this means if we were to do a show IP router OSPF,
we have a couple entries.
That indicates that this neighborship
is now up and working properly.
Now at this point, we don't have a whole lot
of entries in the OSPF table.
This is our first ticket.
We have quite a few tickets to go.
So there are quite a few other things
broken in this environment.
So we wouldn't be expecting to see a whole lot of routes
just yet.
But as we go through this skill, we
should see more and more routes showing up
as we fix more and more issues.
So in this video, we just saw a ticket
that gave us an example of how passive interface works.
Keep in mind, passive interface is usually
really good for client facing interfaces.
Interfaces facing end devices and that could include things
like servers, printers.
Not just end user workstations.
But really, any subnet where we need
to bring the network into OSPF so that we can reach it.
But we don't want to form neighborships either
by accident or because somebody is maliciously
trying to bring another router into our environment.
I hope this has been informative for you.
And I'd like to thank you for viewing.