In our first demonstration, let's implement BFD--
bidirectional forwarding detection--
and link it to OSPF.
Let's use this topology.
So the relative interfaces that we need pay attention to are
interface gig 0/2 here and 0/0 here
and also 0/0 on this switch.
I've already got OSPF currently running.
In fact, let's do this.
Before we implement any type of bidirectional forwarding
detection, let's go ahead and simulate WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
detection, let's go ahead and simulate
a failure in the network, and see how long it takes.
So I'm going to go to R1.
And on R1, let's do a trace route
of getting to 4.4.4.4, which is the loopback interface on R4.
And so the last octet matches the router number.
So this indicates it's going to router 2 and then router 4.
Fantastic.
So if we do a ping--
and I'll do to 4.4.4.4--
and let's say repeat.
Let's go 10,000.
That'll be good.
So this is going to go long.
And that'll give us time to go up
here to switch 2 and go to the console on switch 2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
here to switch 2 and go to the console on switch 2.
And we'll go to interface gig 0/0.
This is the interface going over to R4.
And we'll just shut it.
And what's going to happen is, R4 and that great path
it just had--
it was forwarding to R2.
And R2 was forwarding through the switch interface
over to R4.
But OSPF is going to take probably 30 to 40 seconds
before it converges.
So we'll just let it sit there while it's thinking about it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we'll just let it sit there while it's thinking about it.
Let's talk about BFD.
So we'd go into configuration mode.
And on each interface, we'd specify
that we want to use BFD on the interfaces.
So the interval is how often we're going to send messages.
850 I specified here in milliseconds.
That's 85-- that's a little over 3/4 of a second.
And then the minimum receive is 950, I set.
And then the multiplier is three,
is how many times we're going to miss before we're
going to consider it down.
Now, in a lab environment, or if on older hardware,
you may want to go ahead and set those as high as possible. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
you may want to go ahead and set those as high as possible.
There's also this option called BFD slow timers, which
basically makes it even longer.
So 3,000 represents three seconds.
I'm doing this in the lab.
So I don't blow up my gear and make it unresponsive.
So I'm going to set this in global config.
We'll do all the interfaces for the 850 and 950.
Although the 3,000 really isn't going to be used.
And then we'll go into router configuration mode.
And we're going to say BFD all dash interfaces.
Like, all in, every interface.
That's convenient.
Because then you don't have to go to every single interface. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Because then you don't have to go to every single interface.
However, what we could do is we could just go to the interfaces
and enable them one by one.
Or if we had some interfaces where
we didn't want to use BFD, we would go into those interfaces
and we'd say, no, we'd tell it in the interface
that we don't want to use BFD.
So if you want all your interfaces,
this is the one command, as long as each of the interfaces
has the details on it.
So R1 is cranking out 10,000 pings.
Have a good time.
I'm going to scroll up a little bit though.
And right here, just take a look. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And right here, just take a look.
Each one of those [INAUDIBLE] timeout is two seconds.
And that may be 30--
30 blips, 30 periods.
Or sorry, maybe 20.
So it's approximately somewhere between 35 and 45 seconds,
where our network had no connectivity getting it to R4.
That's because of the latency it took to actually converge.
All right.
Next time I won't do 10,000.
So let's go ahead and while that's finishing,
let's implement BFD on the rest.
So I'll go ahead and just copy all that.
And let's go to R2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And let's go to R2.
And here on R2, we'll right click and paste.
And we'll do that on R4.
In fact, we really only need it in R2 and R4
because we're not going to implement a failure anywhere
else in the network.
So here in R4 we'll implement the same commands.
And this is covering a few more interfaces than R4 has.
But I just wanted one that would capture all these routers
with gig 0/0, 0/1 and 0/2.
Also, the switch-- let's bring that interface back up.
All right.
So that's coming back up.
Now, while that's coming back up, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Now, while that's coming back up,
let me go to-- let's go to R2.
And let me show you how you can verify this.
What we can do is do a show BFD space neighbors.
And then with a question mark, we
can-- there's some options here.
But one-- the core option I want to share with you is details.
And that's going to show us our details about our BFD
neighborships.
So this is-- let me scroll down.
[INAUDIBLE] scooch this up a little bit.
And up a little bit more.
And great.
OK.
So our neighbor, from R2's perspective, for this session
is 10.12.0.1.
That's R1. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
That's R1.
And it says, down down.
And that's because we haven't configured R1 yet.
So it's saying down for that neighborship.
And over here, it's specifying the protocols
that it's currently registered with.
This means that there's BFD, and because we
went to router configuration and we said BFD all interfaces,
it is using--
OSPF is paying attention to the BFD,
or the actual triggers on whether or not
that neighbor or that interface is still
reachable to that neighbor.
So let's finish our configuration on R1. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So let's finish our configuration on R1.
So here in R1, we'll right click.
Paste it in.
And what we should have here, if we do a show BFD neighbors
detail.
Let me do one other one.
Do a show BFD neighbors.
And then we'll do the detail after.
And that is showing us the BFD neighbor.
It shows a state of up and up, which is great.
And also, right here above in the show BFD neighbor detail,
it shows that OSPF is currently associated with it.
So if we did the same thing again-- so we'll go to--
we'll go to switch 2. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we'll go to switch 2.
And on gig 0/0--
and we'll do a $shutdown.
But I'm not going to press Enter yet.
I'm going to go back to R1.
Let's verify our path.
So we're currently going from R2 to R4, which is great.
And let's go ahead and do some pings.
I won't do 10,000, though.
I'll do-- going to do 1,000.
Let me shut that interface on switch 2.
And now, go back to R1.
Now it's still timing out.
I had the missed interval of three.
So it could be up to nine seconds, I believe. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So it could be up to nine seconds, I believe.
Because I had the slow timer set to 3,000 milliseconds.
But there you go.
It's done.
And a lot faster convergence because OSPF is now
paying attention to BFD, who's being hyper--
ahh, is that neighbor there.
And we can have subse--
If you tune it down enough, you can
have subsecond convergence, because OSPF
is paying attention to BFD.
All right.
So that's the example of implementing BFD with OSPF.
And in the next video, let me see what's next.
Ah.
In the next video, let's implement BFD, but this time, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
In the next video, let's implement BFD, but this time,
for EIGRP.
So I'll see you in that video, in just a moment.
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.