In this video, we're going to plan, implement, and verify
virtual links in the hands-on lab.
[MUSIC PLAYING]
And to do this, we're going to start with a working network,
like this, this IPv4 in place.
We have area 0 up here.
If you've been previously with me
in some of the troubleshooting labs,
this is a very similar topology as what we've
been playing with previously.
So here, we have area 0, and area 1, and area 2 over here
on the right.
And as far as, like, what belongs to an area, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And as far as, like, what belongs to an area,
it's really the interfaces on a router that belong to an area.
So in the case of R3, it's got a couple interfaces
that are associated with area 0, the backbone.
It's got another interface that's associated with area 1.
And so, you know, being connected
to two different areas-- area 0, the backbone,
and a non-backbone area-- makes this guy
an ABR, an Area Border Router.
All right.
So here's what I would like to do.
Everything in this network as shown is working.
However, we've been asked to integrate, or include,
additional networks as part of area 78. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
additional networks as part of area 78.
That's it right here.
So we'll go ahead and say we want
to include serial 3/1 on R7.
And also, for grins, we can include serial 3/2 on R8.
And we want to put those into area 78, so that network
right here.
The rest of the topology is 10 dot area number and then
RR for the router, like R1 to 2, and R3 to 4, and so forth.
And then the last octet is always the router number.
But for this network right here, between R7 and R8, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
But for this network right here, between R7 and R8,
it is 10.78.0.0.
Over here on R7, it's dot 7.
Over here on R8, it's dot 8.
The router IDs on R7 and R8 are 7777 and 8888.
So what I'd like to do is let's go ahead
and include this network as part of area 78.
Now, in the lab, you can do this a couple different ways.
We could use network statements.
This is IPv4, is OSPF.
So we can do network statements.
That would work.
Or we could use interface commands.
Or you could try it both ways. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Or you could try it both ways.
In fact, I think what I'll do, as we go through this together,
I might use a network statement on one
and an interface command on the other,
just to give you a round of practice with either one
that you want to use.
OK.
And then once we've added that in area 78,
then we've got a problem.
And that is this 10.78 network, because it has no ABR--
or I should say area 78 because it has no ABR--
it won't be seen by the rest of the OSPF domain.
Those LSAs won't be in area 1.
They won't be in area 0.
They won't be in area 2 because we're not WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
They won't be in area 2 because we're not
following the rules of OSPF, with every area needs
to have an ABR.
So to solve it, what we'll do is we
will create-- let me get red out for this-- we will
create a virtual link.
So the virtual link, the syntax is the router configuration
mode for OSPF for the process that we're using.
And then use the command area, and you
specify the area that's going to be the transit area that's
going to carry this logical virtual link.
And so it would be area 1 in this case, virtual dash link
space, and then from R7, we'd point to the router ID of 3333. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
space, and then from R7, we'd point to the router ID of 3333.
And then when we do it on R3, we'd
point to the router ID of 7777.
And once we've done both sides, then R7,
with this new logical interface, this virtual link 0
interface it's going to create, it
believes logically that it's connected to the backbone.
And as a result, all the routes from area 78,
including the 10.78 network, will now show up
in the entire OSPF domain.
All right, so with that plan in place,
let's go ahead to these two interfaces,
serial 3/1, 3/2 on R7, R8. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
serial 3/1, 3/2 on R7, R8.
We'll include them into OSPF area 78.
We'll verify that those routes, including the 10.78 network,
doesn't show up anywhere outside of this area.
And then we'll fix it with a virtual link.
All right, and here we go.
Let's go to R7.
And on R7, we'll just show IP interface brief,
just to make sure we get the right interface.
So it's the 10.78 network, serial 3/1.
Do a show IP protocols.
Currently, we have network statements WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Currently, we have network statements
to include the loopback, and we have a network statement
to include 10.1 anything in area 1.
So let's use an interface command.
And it's also OSPF process ID 1.
Let's use an interface command to go ahead and enable
serial 3/1 for OSPF.
So we'll do a config t, interface serial 3/1.
And we'll use again IP ospf, a little question mark,
process ID 1 space.
And then we'll go ahead and specify area.
And we're going to use area 78. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we're going to use area 78.
So now if we do a show IP ospf interface brief,
it's going to show us that that interface, serial 3/1,
is associated with area 78.
We have no neighborships.
It's P2P because of the encapsulation
on that serial interface.
Let's go do the same thing for R8.
And we can even form a full adjacency in area 78,
between R7 and R8.
So show IP interface brief, just to confirm
we're on the right interface.
All right.
So there's serial 3/2.
Fantastic. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Fantastic.
Config t.
Oh, and let's use a network statement.
Do show IP protocols.
We'll do a network statement on this one to include it.
All right, so router ospf process ID 1,
based on the output here.
And we'll just do network--
lets go for 10.78.--
not 178.
That's not going to work.
78.0.-- and we'll just put the full 32 bits.
And it's going to be dot 8 on that interface.
10.78.0.8.
And we'll use a wildcard mask saying WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we'll use a wildcard mask saying
we care about every single bit.
And we'll put that into area 78.
We'll then do a show IP ospf interface brief.
And that confirms that it's in area 78.
We also got a full adjacency.
It's like, what?
Yeah.
So we have a full adjacency with another router in area 78.
But if we want to look for this network,
10.78, outside of this area, let's go grab another router.
Let's grab something in the backbone.
How about R1?
Let's go take a look at R1 and see if it WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's go take a look at R1 and see if it
knows about the 10.78 network.
We could also do the same exercise on every other router,
except for R7 and R8, because they're directly connected.
But every other router in the domain
is not going to know about the 10.78.
So let's verify that next.
So we'll go back to-- let's go to R1.
And we'll do a show IP route for 10 anything.
And these are sorted numerically.
And at the bottom here, no 10.78.
Doesn't exist.
All right.
So let's solve this by creating the virtual link. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So let's solve this by creating the virtual link.
So to configure the virtual link,
we actually have a few options here.
We could use R7 to go to the ABR R3.
That would work.
And have area 1 be a transit area.
Also-- oh, I'm so glad I mentioned it.
Because this could be an issue in troubleshooting.
We can't have a virtual link in a stub area.
So if area 1 is a stub area, the virtual link will not function.
It has to be a normal, non-backbone area
that we're going to be going through for this virtual link.
All right.
Having said that, we could go from R7 to the ABR R3 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Having said that, we could go from R7 to the ABR R3
with a virtual link back and forth.
It's a two-way street.
We'd need to put both pieces in.
Or we could also-- because R8 is connected to this area,
area 78--
we could also do a virtual link from R8 up to R4
because it's in the same area.
R8 and R4 are in the same area.
But we have this really slow serial link here.
So that would not be the optimal path.
The optimal path would be this fast Ethernet--
from the backbone's perspective--
would be much faster to reach this network WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
would be much faster to reach this network
than this slow serial link.
Also, make sure you pick an ABR.
R8 needs to pick an ABR in its same area.
So R8 is currently in area 2.
So we need to pick an ABR in area 2.
It can't just pick an ABR that's not in your area
because you can't reach that device.
R8 has no direct knowledge about this ABR over here
on the left hand side, as far as it being an ABR.
OK.
So having said that, let's choose this path
right here between R3 and R7.
I'll walk through the syntax, and I strongly
encourage you to practice along. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
encourage you to practice along.
So if you're on a tablet or something else at the moment,
schedule a few minutes when you're on a computer.
Log onto CBT Nuggets.
Click on the link for the virtual lab
and actually practice doing the virtual link.
Let me clear off my scribble there.
And let's go to-- let's start on R7.
So on R7, we already did our show commands
to verify it's part of 78.
Let's do a config t, router, ospf process ID 1, and area 1.
So this is the transit area we're going WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So this is the transit area we're going
to use for this virtual link.
And we'll do a area 1 question mark.
And we want to make it a virtual link.
So we use virtual-link, space.
And then we point to the--
this is where-- so it says IP address right here.
ID, IP address-- unfortunately, they're saying IP address.
But this is the router ID of the ABR
that we want to build this virtual link for.
So we're going to put in the router ID of 3333. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we're going to put in the router ID of 3333.
And then after that, there's a whole bunch
of options which are beyond the scope of just
basic functionality, so including authentication
and changing hello timers for this logical tunnel interface.
So we'll just put the basics on, and then we'll go to R3
and we'll do it on the other side.
So here on R3.
So R3 is complaining because it doesn't
have its half of the tunnel setup yet.
So we'll fix that.
Router ospf 1.
So I'll do a do show IP ospf, just WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So I'll do a do show IP ospf, just
to verify that getting the right process and everything.
Great.
So we're in the right process ID, router ospf 1.
And let's specify area 1 is going to be a transit area.
And let's specify our virtual link.
So area 1, virtual link.
I started typing in transit area because it was on my brain.
This is what it's becoming, that area 1 virtual link.
And we want to point to the router ID of 7777.
All right, so check this out. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
All right, so check this out.
We just had a full adjacency between R7 and R3.
Now, they are not directly connected.
This is a virtual link, hence the term.
So we have a full adjacency.
So if we go to R7--
and check this out-- and do a show IP ospf interface brief,
see this right here?
VL0.
That's the virtual link.
It is in area 0.
And they have 10.1.57.7 is the egress interface
that we're using to communicate with the other side WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
that we're using to communicate with the other side
of that tunnel.
And right here, it says we have one neighbor that we see,
thus the count.
And the first one is the F for Full adjacency.
We've got a full adjacency.
Fantastic.
And check this out.
If we do a show IP ospf and press Enter
and scroll down a little bit, now it shows us
they have area 78, which we configured earlier.
I'll scroll up a little bit now.
We have area 1, which we were in before.
And now we are connected to the backbone. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And now we are connected to the backbone.
This makes R7 effectively, logically, an ABR.
So now there's routes right here.
Go back to our drawing.
Anything in area 78, including the 10.78 network,
should now show up in OSPF.
So if we go up to R1, which didn't
have that route previously, let's go back to R1.
And here on R1, we'll just use the up arrow key again.
Hit the spacebar a few times.
There is our network, 10.78.0.0.
And if we went to a router and tried
to ping an address on that, like let's say-- let's go to R6. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
to ping an address on that, like let's say-- let's go to R6.
Now, R6 is over here in area 2.
And it's going to learn about that network via an LSA type
3 that's coming from R4, the ABR.
So you might think, well, gosh, we're just so close right here.
Why would we go all the way around the horn to get there?
And that's because that's how it's
being communicated via OSPF.
Let's just verify that's true.
And then if you want, we can tweak with a static route,
and we can change the rules.
Let's go to R6. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Let's go to R6.
And here on R6, we'll just do a show IP route.
We'll look at all of them.
That's fine.
And there is our inter-area route.
That route exists in area 78.
R7 is acting as an ABR, offering the summary
LSA in the backbone, which then R4 sees and then advertises
as an LSA type 3 to area 1.
And that's how R6 learned about it.
So R6, if we did a trace to 10.78.0.-- WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So R6, if we did a trace to 10.78.0.--
let's go to 8--
it's going to go all the way around the horn.
So from R4, to R2, to R1, to R3, to R5, to 7, finally to 8.
So that's the long way home.
But that's the way OSPF works.
Now, if we wanted to change that.
We thought, you know, we know better,
or we'd like to have R6, for that specific network,
go this way.
We can just play a game called AD.
And so we could just create a static route,
which is going to have a lower administrative distance.
OSPF is 110 by default. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
OSPF is 110 by default.
So if we create a static route that says, hey, Mr. R6,
to get to the 10.78 network, just
use the next hop of fa 4/1.
That is going to have a default administrative distance of 1
because it's a static route pointing to a next hop.
And as a result, it would be used instead of the route that
says go this way.
So if we wanted to-- just on R6, because it's a slow link right
here--
do a static route, we could.
I think we should, just for fun.
And let's do that now.
Again, this is bonus points.
You don't have to do this.
But I want to help reinforce the concept of routing,
and following the rules, and how routes are chosen. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and following the rules, and how routes are chosen.
So we'll go back to the CLI.
We'll do a show IP route, just to confirm here.
So this inter area route has an administrative distance of 110.
So if we create a static route, IP route.
And let's go for 10.78 anything.
All right, that'll work.
And let's say the next hop from R6's point of view
is going to be 10.2.68, which is the link between R6 and R8. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
is going to be 10.2.68, which is the link between R6 and R8.
And the IP address of R8 is dot 8.
And by default, it's going to have
an administrator distance of 1.
So we can just leave that, press Enter.
Show IP route, hit the space bar a few times.
This can be at the very bottom.
And-- oh, I put a 16-bit route in.
It says, Keith, you know that whole thing
about choosing the best route, those are different routes.
So if we were to ping right now again or trace, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So if we were to ping right now again or trace,
it would choose the longest match,
which would still be this guy.
So that means I need to go back.
And I need to make a 24-bit route so that it's the same.
So let's go ahead and do this.
I'm glad that happened.
Good exercise.
Show IP route.
And there we go.
So there's our 24-bit route.
Because the administrative distance is 1,
it's pushing out the OSPF route.
It's no longer on the routing table.
Now, if we did a trace, I think I still WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Now, if we did a trace, I think I still
have-- there we go-- to 10.78.0.8,
now it's going directly down to R8.
And if we shut down that interface-- let
me verify the interface here.
If we shut down fa 4/0--
let's do that.
So interface fa 4/0.
And it is shut down.
Because that next hop is no longer reachable,
that static route just fell out of the routing table.
And now if you do a do show IP route
and look at 10.78 network, it's now back
as the OSPF learned route with a administrative distance of 110. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
as the OSPF learned route with a administrative distance of 110.
And once again, if we did a traceroute to that address,
it would take the long way around the horn.
All right, so we still have connectivity.
So in this video, we've taken a look
at implementing and verifying a virtual link in OSPF version 2.
And I would encourage you to take a few minutes and practice
with this.
Because in the very next lab and video,
we're going to take a look at troubleshooting OSPF version
2 and virtual links.
And just like in our previous troubleshooting videos,
I'm going to include at least one issue related WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
I'm going to include at least one issue related
to a virtual link that may be required or not working
and at least one or two other problems.
And that way, you can approach the lab with eyes wide open
and not know exactly where the problem is going to be
or what it's going to be related to,
and actually tweak and test your troubleshooting skills, which
will make you a better troubleshooter and more
familiar with how the technology works in the first place.
So we'll see you in that video in just a few moments.
Meanwhile, I hope this has been informative for you,
and I'd like to thank you for viewing.