All right, if you're ready for another troubleshooting lab,
so am I. Let's begin.
[THEME MUSIC]
And for this lab, we have R8, which has a loopback interface,
and that loopback interface is loopback 50,
and it has the IP address of 10.50.50.50.
And what I'd like to do is not modify
the details of that loopback 50 or it's OSPF properties.
But at the same time, I would love for PC7, right here, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
But at the same time, I would love for PC7, right here,
to be able to ping 10--
right here, ping 10.50.50.50.
So our mission, should we choose to accept it,
is to go ahead and troubleshoot this
so that we can leave this loopback
interface and its OSPF properties
as it is and still have reachability to it.
So there's going to be at least one problem with authentication
in this lab, and also very likely, one other problem.
And what I did was I created this lab yesterday
along with a few other troubleshooting labs, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
along with a few other troubleshooting labs,
and I don't remember all the details of all
the specific problems for this.
So it'll be a little fun for me, too.
However, I would recommend this--
instead of just watching me do it from soup to dessert,
I would recommend pausing it right here,
clicking on the link for the Virtual Lab
if you're logged on from a computer
to the CBT Nuggets website, and give it a shot.
Get that hands-on practice.
Then when you're ready to compare notes and watch
me do the walkthrough, then you can go ahead and resume me.
So I'm going to give you a moment right now to go ahead
and pause, and in a moment we'll go back,
and we'll walk through the solution. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and we'll walk through the solution.
And so here's what I propose we do.
Let's just go to R7 and see whether or not we have a route
to 10.50.50.50, and let's start from there.
And then we'll identify where, in the network,
that route is showing up.
Then we can backtrack from there if we need to.
So here in the topology, we'll go to R7,
and we'll do a show IP route, OSPF learned routes,
and these are going to be sorted for us.
We're looking for 10.50.50. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We're looking for 10.50.50.
I don't see it.
Let's go take a peek at a backbone router,
and let's pick on R4.
So we'll go up to R4 because it's also an area border
router for area 2.
So on R4, we'll do a show IP OSPF--
a little ahead of myself.
Show IP route OSPF, and it doesn't know about the 10.50
network.
And let's go talk to R8.
Does R8 know it?
Let's do a show IP route connected.
WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
There it is.
I just want make sure the route exists somewhere.
So it's here, and let's do a show IP OSPF interface brief.
And that says, for loopback 50, that it is in area 50.
So the challenge here about having a loopback interface,
or any interface that's associated with area 50,
is that who is the ABR for area 50?
And if we go back to the topology
diagram, and I bring a pen up--
so we've got loopback 50, which is in area 50 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
so we've got loopback 50, which is in area 50
based on the output we just did.
And there is no area border router.
I mean, R8 is not an area border router.
It's not connected to the backbone,
and R6 is not connected to the backbone.
R4 is.
So in this topology, that network
is never going to be learned by the rest of the OSPF domain
because it's not following the rules.
So we described the solution to this a couple videos
go, in the set of videos, regarding a virtual link.
We'll have more coming up and details on that,
but we need a virtual link from R4 to R8.
And that virtual link-- WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And that virtual link--
I'll put it in a different color here--
is a logical connection between R8 and R4,
this virtual link, which allows R8 to logically become
part of the backbone.
And then guess what-- it's an area border
router between the backbone area and this area 50.
So I think, in the output, I think I saw that it existed.
Let's do a few show commands and verify that,
and if we do have a virtual link,
there shouldn't be a problem with this.
But let's go take a look and just verify the virtual link
on both R4 and R8. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
on both R4 and R8.
So here on R8 with the output of show
IP OSPF interface brief, see this thing right here--
VL0?
That's for a virtual link.
We can also do a command.
And if this is brand new, have no worries.
We'll take a closer look at it in a separate set
of videos on virtual links.
But if we do a show IP OSPF virtual link, plural,
it again show us our virtual links.
So this is R8 with a virtual link to 4.4.4.4.
So you point to the router ID, not the actual IP address--
the router ID.
So it looks like the configuration is correct
as far as the peer, 4.4.4.4, but it says it's down. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
as far as the peer, 4.4.4.4, but it says it's down.
And let's go ahead and take a look at R4,
and we'll do a show IP OSPF neighbors
and show IP OSPF interface brief.
And it's got a virtual link as well,
and it also says it's down.
So if we do a show IP OSPF virtual links--
you know what we could do?
Let's do a debug. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's do a debug.
Debug, debug-- degub?
Debug of IP OSPF adjacency, and maybe that'll
give us a clue as to what's going on.
So that's local to R6.
So we have these hellos being sent out.
Nothing negative to report yet.
That looks OK.
Well, here on R4, let's do this. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Well, here on R4, let's do this.
Let's do a show IP OSPF and press Enter,
and this says that the area has message digest
authentication for area 0.
And if we take a look at R8, when we create a virtual link,
that literally-- hmm, strong word, Keith--
that logically puts that router, that
wasn't previously in the backbone area,
in the backbone via that virtual link.
So if we do a show IP OSPF on R8,
it's going to show us that it's got WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
it's going to show us that it's got
an interface in the backbone.
That's the logical interface with the virtual link,
and that has no authentication, and that's
why we're not peering.
So with authentication, if we have MD5 authentication
for the area, we need to tell R8 that, hey, for area 0,
we're using MD5 authentication.
Even if we don't have a password configured,
we have to agree on the actual type.
So to start our troubleshooting, let's do this.
Let's go to config t router OSPF 1 and area 0, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's go to config t router OSPF 1 and area 0,
and authentication is message digest.
And if that was the only problem,
we should get an adjacency with R4 over the virtual link.
However, I'm not seeing any messages pop up,
so let's do a show IP OSPF interface brief.
There's our virtual link.
It still says down. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
It still says down.
Let's keep troubleshooting then.
So let's go back to R4, and I'm going
to turn off the debugging here.
Let's do a show IP OSPF.
Just want to verify I got the type right.
So the backbone area has message digest authentication,
and if we go to R8, show IP OSPF,
Here it's showing area has message digest authentication.
So as far as the authentication being enabled on R8, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So as far as the authentication being enabled on R8,
that looks like it's solved.
But we're still not--
our virtual link still has a problem.
Show IP OSPF interface brief--
so there it is right there, as the virtual link still
says it's down, so let's do a show IP OSPF neighbors.
We've got R6 as a neighbor, and let's look
at the routing table.
Show IP route OSPF for OSPF--
oh, that's not good. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
oh, that's not good.
So we're learning just a few-- so
that 2 right there represents-- in that second octet.
That represents the-- I matched those to the area.
So we're not learning about any routes outside of area 2.
So let's go to R6 and take a look
and make sure it has a neighborship with R4
because it would have to have an adjacency there that works,
too.
So let's go back to R6, and on R6,
let's do a show IP OSPF neighbors.
So it's not neighboring with R4, and the question is why?
Let's do a show IP OSPF interface brief, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's do a show IP OSPF interface brief,
and looking at our topology--
oh, I can kind of gauge it off this third octet.
That's the router number.
So between R4 and R6, this is the network,
and it's using serial 3/2.
And the neighbors and--
so the full and count numbers are both 0.
That means we don't see any other OSPF neighbors,
and we're not fully adjacent with any OSPF neighbors.
So let's identify why that might be.
Let's do a show IP OSPF interface for serial 3/2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's do a show IP OSPF interface for serial 3/2.
So right here, it doesn't specify
any type of authentication for that interface.
Let's do a show CDP neighbors, and off of our 3/2 interface,
we have 3/1 up on R4.
Let's go take a look at R4 and show IP OSPF interface brief.
So we have OSPF enabled on that interface. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we have OSPF enabled on that interface.
The network type is point to point, which matched R6.
Let's do a show IP OSPF interface for serial 3/1,
and this also doesn't specify any type of authentication.
So I was thinking that we were going to have an authentication
issue there, but what I do see in this output is
passive interface.
So what passive interface does, it says, hey,
you know that network you're directly connected
to on this interface, 3/1?
Go ahead and include that in OSPF,
but don't bother doing hellos. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
but don't bother doing hellos.
And that's what it's literally saying there.
We have passive interface for serial 3/1,
and that's why we're not neighboring with R6.
So let's fix that.
Interface router OSPF 1, no passive interface
for serial 3/1, and we'll just hope for a neighborship.
There we go-- full adjacency.
So now that we've corrected the adjacency between R4 and R6,
and we've also corrected the authentication
statement for area 0 on R8, let's go back to R7. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
statement for area 0 on R8, let's go back to R7.
And let's do that same command again, show IP route OSPF,
and see whether or not we have 10--
we don't.
No 10.50.50 that I see yet.
Well, let's go back to R4 and see if R4 can see that route,
so show IP route OSPF.
It sees 10.50.50. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
It sees 10.50.50.
Let's go to R3, which is this guy right here,
this area border router.
Let's see if he sees it.
So on R3, show IP route OSPF.
Oh, he sees it.
Well, let's go back down to R7.
Maybe we just didn't allow enough time for it to converge.
Show IP route OSPF, and he sees it.
All right, I just wasn't--
I was like, oh, link state, it's going to be really fast.
Well, it takes a second or two, especially
in a lab environment.
All right, so let's verify R7 can ping it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
All right, so let's verify R7 can ping it.
So we'll do a ping.
Let me just do a show IP route connected.
Let's source it from the same network where our PC is,
which is the 101.7--
this interface right here.
Just going to copy that, and we'll do a trace
to 10.50.50.50.
I'm going to source it from that interface,
and that way, we have--
that way, we can verify full reachability
in here, a full path.
Great, let's go to PC7 and ping that address one more time. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Great, let's go to PC7 and ping that address one more time.
In fact, we can trace it, too, right from that PC.
Just going to copy that command.
So PC7-- he's got a default gateway pointing to R7.
Let's go ahead and right click, and we are in the business.
So that trace, by default, this little VM uses UDP.
And so that port wasn't open on that final destination.
So if you want to do a dash capital P space 1, that says, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So if you want to do a dash capital P space 1, that says,
I want to use Protocol 1 ICMP instead of UDP by default.
So it'll give us the same trace, except the last hop says,
oh, this looks like a ping request, and can respond back.
And we don't get the error about a destination port unreachable.
So in this troubleshooting lab, we've had the opportunity to do
some hands-on practice in troubleshooting neighbor
adjacencies based on--
what did we have between R4--
oh, passive interface between R4 and R6.
We also had an authentication mismatch
between R8, which had a virtual link
and was participating in area 0, and area 0 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and was participating in area 0, and area 0
had MD5 authentication.
So those are the two pieces we had to solve for this network
to function.
So thanks for joining me in this set
of troubleshooting labs regarding
OSPF version 2 for IPv4.
In our next set of videos, we're going
to do some troubleshooting again, once again
with authentication and issues that can come up,
except this time, we'll focus on the world
of IPv6 and OSPF version 3.
So I look forward to seeing you in that set of videos as well.
Meanwhile, I hope this has been informative for you,
and I'd like to thank you for viewing. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and I'd like to thank you for viewing.