- [Narrator] In our previous video,
we took a look at
a Cisco proprietary first hop redundancy protocol
or an FHRP,
and it was HSRP the hot standby router protocol.
But here we want to take a look at
an industry standard first hopper redundancy protocol.
It's called VRRP,
the virtual router redundancy protocol.
The basic purpose in life of VRRP is the same as HSRP.
We want to have a PC.
I have more than one option
for getting off from this local sub-net.
So in this example,
we've got a virtual router,
again with an IP address of 10.1.1.1
just like we had on our prior example,
but instead of having an active router,
that's what we call it with HSRP,
with VRRP, the router that's actively fording the packets,
we call that the master router.
And instead of saying we have a standby router,
the terminology is a bit different.
We have a backup router.
And instead of having a hello interval that defaults
to three seconds,
we have an advertisement interval
that defaults to one second.
So again,
normally traffic flow in this topology
is going to go through R1 out to the internet.
But if something happens to R1,
you see router R1 going down,
router R2 is going to take over the master roll
and nail packet flow is going to go through router R2.
Now let's review some of the characteristics of VRRP.
First of all,
as we already said it is an industry-standard,
it's not Cisco proprietary.
So if you've got a mixed vendor environment,
this may be your first hop redundancy protocol of choice.
It's defined by RFC 3768
and instead of having active and standby routers,
it has master and backup routers.
And with HSRP,
we talked about the Mac address format
and it was a bit different
for version one versus version two.
Well here,
the Mac address format is going to be like this
and the last two hexadecimal digits
that's going to represent the VRRP group number.
And we said with HSRP,
the preemption feature was disabled by default.
Well here it's enabled by default.
And with HSRP we said
the default hello time was three seconds.
Well here the master advertisement interval is one second.
So we send out updates more frequently by default.
Now here's where it gets quite a bit different.
With HSRP, we had the whole time,
which we said had to be at least three times the hello time
and it defaulted to 10 seconds.
Well instead of having them a whole time with VRRP,
we have something called the master down interval
and it's a bit complex.
It's three times whatever
the master advertisement interval is,
it defaults to one.
So three times one is three,
so it's three by default.
Plus.
Whatever the result is of this formula,
we take a 256 minus the priority on an interface,
We divide that by 256,
we add that to three by default,
and that's going to be our master down interval.
So you can see this is going to be a little bit
more than three times the master advertisement interval
and we send out the master advertisement
to a multicast address of 224.0.0.18
and something else that's different from HSRP
is that with HSRP we said that the virtual routers
IP address had to be different than
the physical IP address on a router.
But here you might have noticed in the topology,
I had R1 with an IP address of 10.1.1.1
and that was the default gateways IP address as well.
Yeah, with VRRP,
I don't necessarily think it's the best practice,
but I want you to know it's possible.
We can have the interface's IP address
be the same as the virtual IP address.
Now let's go ahead and take a look at
the configuration of VRRP.
What we're going to do is use the same
typology that we used for HSRP to set up VRRP.
So even though VRRP would let us use a
physical interface as IP address,
as the virtual IP address,
we're going to do things just the way we did them with HSRP.
The terminology is a bit different.
In this case,
router R1 is our master router
and router R2 is the backup router.
Let's go to router R1 first
and we'll do a very similar configuration to HSRP.
I'm going to go into interface gigabit 0/1
and instead of saying standby
and giving a group number,
I'm going to say VRRP
and give a group number,
and we're going to be servicing the IP address of 10.1.1.1
and I want this to be the master router,
so I'm going to set the priority to something higher
than 100 which again is the default.
Notice that we're now the master router,
it says on screen.
I'm going to say VRRP group 10 priority 110.
Now let's go configure router R2,
on router R2 let's go into interface gigabit 0/1
and we'll say VRRP
group 10 IP 10.1.1.1.
Now I'm not going to set the priority here because
I want it to have the default priority of 100
or something else you might have noticed
I didn't say anything about preemption,
and that's because preemption is enabled about default
with VRRP.
For verification,
instead of doing a show standby brief,
let's do a show VRRP
brief command
and notice the time column
shows the master down interval.
The way to read this,
this 3609 that means the master down interval
is 3.609 seconds.
The units of measure here,
it doesn't tell us,
but the units of measure are milliseconds
and there's nothing under the own column you'll notice
because this router doesn't have a physical interface
with an IP address matching the virtual IP address.
If we did, that's something we couldn't
even do with HSRP,
but if we did it would show that we are the owner
on our physical interface of the virtual routers IP address.
Now let's take a look at this output on router R1,
let's go over to router R1
and do a show VRRP brief,
and here you're going to notice that
the time is a bit different,
it's 3.570 seconds.
It's different than the master down interval on router R2
which was 3.609 seconds.
Let's see how this time is derived.
Let's do a show VRRP,
and we see that the master advertisement interval is
the default of one second and we said
that we had to go through this formula
in order to calculate the master down interval.
Let's go over to a calculator
and do this calculation together for this interface
on router R1 with a priority of 110.
Okay, that formula was three times the
advertisement interval,
so that's three times one that's three seconds.
Plus what's called the skew time.
Let's calculate the skew time
and then add three.
The skew time here on router R1,
is 256 minus the priority on that interface,
and we set the priority to be 110.
We take that value
and we divide by 256.
We then add that number,
which is now the skew time,
we add that to three.
Again, that was three times the advertisement interval,
which was one,
three times one is three,
three plus this,
I'll say plus three
and this gives us 3.570 seconds
and let's go back to our router.
And we see that our master down
interval is indeed 3.570 seconds.
And here in this video,
we're not going to go through configuring tracking
and authentication because they are configured
and they work identically to how they work
and were configured with HSRP.
And that's a look at some subtle differences
in the industry standard VRRP configuration.