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 [music]

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Now we're going
to take a look at

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SLAAC configuration or Stateless

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Address Automatic Configuration.

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The basic idea here, we're going

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to be using the
same topology that

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we used in our previous lesson.

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Again, we're going to
be focusing on VLAN 36.

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But this time, we're going to be

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looking more at the
router 6 side.

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Well actually, sort of both
router 3 and router 6.

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Basically what this
is going to be for

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is to have router
6 automatically

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pull its address from router 3.

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The basic idea, before
we jump too far

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into this as far
as configuration,

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stateless autoconfiguration,

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again is a replacement
so to speak -

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an alternative method maybe
is a better way to say it -

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for DHCP. and the idea is we can

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have a device
automatically learn

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certain information.

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The way SLAAC is right now,

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although I know there
have been some

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RFCs proposed to update SLAAC,

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but what you're
going to get so far

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is from your router
advertisement -

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and we're going to see this here

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in just a minute -

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but from your router
advertisement,

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you're going to get the prefix

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length and the global address
being advertised by the router.

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The client is going to take that
information and essentially make

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up his own client
portion of the address.

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You will then also
use the router

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advertisement to learn who your

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default gateway is.

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So for warehouse scanners

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and various sensors and so on,

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that's all fine.

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and that's what we're
going to start with here.

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The problem comes in of course,

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is if you need
actual DNS servers,

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things like that.

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That's where this
falls a little short,

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and where they're proposing

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to do some changes to the RFCs.

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So the first thing we're going
to take a look at is actually

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configuring the
IPv6 router side,

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and in our case, that's going to

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be router 3. So this is
where we left off before.

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I just want to show
you one thing here

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real quick that I did
do automatically

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before we started on
all these routers.

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If we were to say do show
run pipe include ipv6,

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just want you to see that
these devices automatic--

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not automatically.

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We had to enable
it, but I already

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turned on IPv6 unicast routing

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and IPv6 CEF. Now,
the IPv6 unicast

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routing wasn't really required

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for what we did in our
previous section,

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just assigning addresses
to interfaces and so on,

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no problem at all.
But as soon as

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you want to start doing routing,

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then of course,
you'll need that,

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and the reason I'm bringing this

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up here with SLAAC
is if I were to say,

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do debug ipv6 neighbor
discovery, or advertise.

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We can just do neighbor
discovery here.

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And as soon as we start looking

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at this, we're going to see that

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router 3 is already
sending out -

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there's the first
one right there -

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he is sending out a
router advertisement

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on his link local to--
and that the FF02::1,

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that is the all nodes
multicast address.

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So the FF02 means link local,
so it's a link local multicast,

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just on this segment, and ::1
on his FA00.36 interface,

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he advertises the MTU.

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He advertises the
prefix, and he also

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advertises a valid and
preferred lifetime.

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The valid lifetime is how

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long you're allowed
to use that prefix.

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The preferred lifetime is

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how long you originate traffic

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from that prefix.

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Now this, as you can see,
is happening automatically.

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I didn't have to do anything on

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router 3 except
make it a router.

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As soon as you turn on
IPv6 unicast routing,

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you're going to get router

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advertisements going
out the interface.

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Now, if I said IPv6?

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on the interface,

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there's quite a few
things here we can do,

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of course. Most of this going to

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be that we're talking
about right now,

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is going to be on the
neighbor discovery.

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So if we said ipv6
neighbor discovery

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is the thing we're going to

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focus on right this second.

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Couple of things we
can do: first one

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is the RA, which is the router

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advertisement message
we're talking

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about right now.

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And a couple of things
you can do: first off,

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you can change the lifetime,
you can change the interval,

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hop limit of how far it'll
go, of course the MTU.

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And if you didn't
want to do this,

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because a lot of people look

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at this and go, What
if I'm going to use

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some other method
to configure this?

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I don't want this neighbor

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discovery and router
advertisement message,

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then you can suppress it.

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I will say this, though.

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Before you choose
to suppress the

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router advertisement messages,

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you really need to think through
what you're doing here.

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The reason I say
that is, when we

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get to DHCP a little bit later,

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you're going to discover that

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there's no option
to advertise your

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default gateway or default
router in DHCP in IPv6,

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that's gone. Your default
gateway next hop,

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whatever you want to
call, it is going

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to come from a router
advertisement message.

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So before you do shut this off,

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you probably don't want to

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just do that unless
you know why.

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But we can suppress it, we can

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change the interval
to make it run

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a little faster. As you can see
it doesn't go very often here.

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It doesn't really
need to because

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when the client comes online,

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it will send out a
solicitation message.

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In fact, rather than
speeding it up,

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because it gets a little harder

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to tell here, I'm
going to let it go

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a little bit slower
for right now,

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and as we bring up router 6

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as the client, we
can see that it's

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not like the client
is really going

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to sit there, and
by the way when

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I said it's slow,

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notice that this message
right here-- where was it?

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 I've looked at a couple
of things since then.

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Here's him advertising 36, and I
don't have date time stamps on.

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If you notice, he
hasn't advertised

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it for a while and the last one

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was way back up here where he

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advertised 36 when
we first started.

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We have some other
messages going on,

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but that's him advertising 36.

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There's him
advertising 36 again.

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Do show ipv6 interface FA0/0.36.

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The default is 200 seconds.

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Again, we could speed this up a

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little bit just to
show you how the

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command works.

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I didn't actually type it in.

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We could change this  to

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show you how it
works without going

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crazy with it.

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Let's just say once
every 30 seconds.

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Then if I look at the
interface again,

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that'll of course, trigger
it to go right away.

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Now, it's going
every 30 seconds.

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Now again, the reason I say
this isn't all that critical,

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honestly, is when the
client comes online,

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he's not just going
to have to sit

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there and wait until this guy

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sends an advertisement.

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That's not how it works.

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The only reason
that we even have

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these timed updates being sent

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every so often, is
in case you go and

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change the prefix
being advertised

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or you change the valid
and preferred lifetime.

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If you change any of that,

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then you're going to
want it to update

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the clients that have already

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gotten this information
previously.

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That's the only reason for
the timed update anyways.

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If it's not the fastest
thing in the world,

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the default's 200 seconds,

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a lot of people go,
I don't want a

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machine taking 200 seconds until

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it gets an address.

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That's not what this is for.

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This periodic
update is literally

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just to refresh anything.

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So if I were to, again,
just for an example,

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say instead of
interval, we could

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say-- let's take a look here.

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Let's do lifetime.

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So we'll say it's the
lifetime-- I'm sorry.

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That's just for the
router advertisement.

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We need to do prefix for
the one I'm looking at.

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So we'll say prefix, and
then we'll say default,

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and set the valid lifetime.

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So just for the sake of
something to do here,

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we'll say-- we're going to
say it's valid for 600.

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This is of course in seconds.

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So that'd be 10 minutes.

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It's preferred for
five minutes. So if

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we just change
something like that,

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next interval - there we go -
we'll see these get changed.

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And by the way, you might have

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noticed too, as soon
as I changed it,

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notice that the IOS just kicked
off another update anyway,

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so it's not even-- a lot
of changes you make

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are going to trigger

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an update anyway, even if
it's not the 30 seconds yet.

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But in any case--
so here's router 3

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over here, advertising
the information.

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Now let's go take a look
at the client side.

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So let's go over to router
6 and we're going to say,

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ipv6 address, and the
command is auto config.

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Now, just so you know, before I

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type this - do show
ipv6 interface brief -

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he's going to have no address.

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We're looking at this interface
right here once again.

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And I just want you guys to

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understand that if
this were Windows,

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Linux, MAC, just about any other

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desktop operating
system out there,

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end device, anything like that,

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assuming of course
it's IPv6 enabled,

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it would've already pulled
this information, most likely.

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Most things are
automatically set

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up to do SLAAC and
they'd already

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be going. You'd already
be done. But the router,

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 understandably I hope,

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is sort of designed
to be a router,

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not an end device,

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and therefore you have
to actually tell it,

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you know what, get your
address from auto config.

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Soon as we do that,
if we hop over

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to router 3, we should've seen--

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there we go. So this
is the other guy

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sending a router advertisement--

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oh, here we go. I wasn't
looking up far enough,

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I was looking for the solicit
message, there it is.

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Sending a solicited RA.

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Notice, he didn't wait
for a time or anything.

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Right here, he received an RS,

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which is a router
solicitation message.

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So he received the
router solicitation

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on his interface from ::.

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Basically, it's from--
the guy doesn't know.

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He's saying, Who's the router?

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I need to know
what my prefix is.

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Basically he's saying,
I know nothing.

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00:12:24,080 --> 00:12:25,704
So I, of course, send him that

257
00:12:25,704 --> 00:12:28,935
information right
away and that's it.

258
00:12:28,935 --> 00:12:30,018
Now the rest of this, of course,

259
00:12:30,018 --> 00:12:32,407
is going on with some
other information.

260
00:12:32,407 --> 00:12:33,767
But you can see,

261
00:12:33,767 --> 00:12:35,192
that's the important part I want

262
00:12:35,192 --> 00:12:42,326
to show you right now is that,
we got the information.

263
00:12:42,326 --> 00:12:45,992
Do show ipv6 interface brief,

264
00:12:45,992 --> 00:12:52,160
and he's pulled that
prefix from router 3.

265
00:12:52,160 --> 00:12:53,915
Now, something else you may

266
00:12:53,915 --> 00:12:56,019
want to do-- and
this sort of goes

267
00:12:56,019 --> 00:12:58,077
back to our previous
lesson, and this

268
00:12:58,089 --> 00:12:59,996
is completely
optional, of course.

269
00:12:59,996 --> 00:13:02,484
There's two things here
that are optional.

270
00:13:02,484 --> 00:13:05,655
First, you might want
to control the address.

271
00:13:05,655 --> 00:13:07,545
Because again, that's not the

272
00:13:07,545 --> 00:13:10,904
prettiest host address
in the world,

273
00:13:10,904 --> 00:13:13,068
especially if this is a router.

274
00:13:13,068 --> 00:13:15,052
You're going to be
doing traces and

275
00:13:15,052 --> 00:13:16,256
you're going to be doing pings,

276
00:13:16,256 --> 00:13:18,696
and you're going to
be doing network

277
00:13:18,696 --> 00:13:20,903
diagnostic and troubleshooting.

278
00:13:20,903 --> 00:13:22,760
If that's an end
device, if that's

279
00:13:22,760 --> 00:13:27,052
Sally's workstation out in
accounting or something,

280
00:13:27,052 --> 00:13:31,328
just like DHCP, we don't really
care what it's address is.

281
00:13:31,328 --> 00:13:35,233
But this is the device we may
actually have to troubleshoot.

282
00:13:35,233 --> 00:13:37,957
So you may not--
you may want to--

283
00:13:37,957 --> 00:13:39,618
a lot of times with our routers,

284
00:13:39,618 --> 00:13:41,455
I'm sure you all
understand this,

285
00:13:41,455 --> 00:13:43,590
that we would
literally just have

286
00:13:43,590 --> 00:13:45,331
them all statically assigned.

287
00:13:45,331 --> 00:13:47,629
But in the interest of showing
you all the different options,

288
00:13:47,629 --> 00:13:49,215
we're not going to do that.

289
00:13:49,215 --> 00:13:51,375
So we can combine this,

290
00:13:51,375 --> 00:13:57,878
what we looked at before though,
and say ipv6 address FE80::6,

291
00:13:57,878 --> 00:14:03,365
link local, and actually control

292
00:14:03,365 --> 00:14:06,897
that he's getting
this part from SLAAC,

293
00:14:06,897 --> 00:14:10,845
but then since we hard coded
the link local address,

294
00:14:10,845 --> 00:14:13,930
and therefore his
IPv6 client ID,

295
00:14:13,930 --> 00:14:16,267
we've now also controlled what

296
00:14:16,267 --> 00:14:20,536
his host portion is going to
be for that SLAAC address.

297
00:14:20,536 --> 00:14:26,428
So that's one optional
thing we could do.

298
00:14:26,428 --> 00:14:28,960
The other thing we can do is

299
00:14:28,960 --> 00:14:33,304
actually control
that default route.

300
00:14:33,304 --> 00:14:34,980
Remember we said
with SLAAC - and let

301
00:14:34,992 --> 00:14:36,679
me switch back over
here real quick -

302
00:14:36,679 --> 00:14:39,801
we're looking right now of
course at configuring the

303
00:14:39,801 --> 00:14:41,212
client device.

304
00:14:41,212 --> 00:14:42,669
That's the main thing.

305
00:14:42,669 --> 00:14:44,946
The client device
should be getting

306
00:14:44,946 --> 00:14:46,524
some basic information here.

307
00:14:46,524 --> 00:14:49,578
It needs to get the prefix,
which we've gotten - check.

308
00:14:49,578 --> 00:14:51,777
It needs to get the
prefix length.

309
00:14:51,777 --> 00:14:54,641
/64 in our case - check.

310
00:14:54,641 --> 00:14:58,552
It needs to get-- well,
see here's the next part.

311
00:14:58,552 --> 00:15:03,151
 It needs to get its default
gateway or its default router.

312
00:15:03,151 --> 00:15:06,977
Now, again, in the
case of a normal

313
00:15:06,977 --> 00:15:10,803
desktop operating
system end device

314
00:15:10,803 --> 00:15:15,785
acting like a SLAAC client,
we'd probably be done.

315
00:15:15,785 --> 00:15:21,309
Once again, because this is a
router, we're not going to be.

316
00:15:21,309 --> 00:15:22,641
I'm going to show you
that in one second,

317
00:15:22,641 --> 00:15:24,455
but just real quickly
here, I wanted

318
00:15:24,455 --> 00:15:26,192
to show you what we're doing

319
00:15:26,192 --> 00:15:28,088
right now, of course, is how we

320
00:15:28,088 --> 00:15:30,072
control the host
portion with the

321
00:15:30,072 --> 00:15:31,957
link local address.

322
00:15:31,957 --> 00:15:34,468
Here's the thing with
the default gateway.

323
00:15:34,468 --> 00:15:40,479
If I now said do
show ipv6 route,

324
00:15:40,479 --> 00:15:45,284
notice that he's got the /64,

325
00:15:45,284 --> 00:15:50,318
and if you look at your legend
up top, notice that ND--

326
00:15:50,318 --> 00:15:52,699
sorry, I'm highlighting
the wrong thing,

327
00:15:52,699 --> 00:15:54,558
NDP is that he learned that from

328
00:15:54,558 --> 00:15:56,843
a neighbor discovery prefix.

329
00:15:56,843 --> 00:15:59,374
What he does not
have, and you're

330
00:15:59,374 --> 00:16:01,197
going to look over the
routing table here,

331
00:16:01,197 --> 00:16:05,904
these are all locally
connected interfaces.

332
00:16:05,904 --> 00:16:07,913
That's, of course, the interface

333
00:16:07,913 --> 00:16:10,949
that we're talking
about right now.

334
00:16:10,949 --> 00:16:13,780
And I know you guys
don't have the

335
00:16:13,780 --> 00:16:15,721
diagram right in front of you,

336
00:16:15,721 --> 00:16:21,409
but that is the VLAN 69
interface - both of those.

337
00:16:21,409 --> 00:16:23,796
This, of course,
is his loopback,

338
00:16:23,796 --> 00:16:26,552
and this is simply for
multicast traffic.

339
00:16:26,552 --> 00:16:30,554
Anything starting with
FF/8 is multicast.

340
00:16:30,554 --> 00:16:34,906
So that's just basically telling
him to receive any multicast

341
00:16:34,906 --> 00:16:36,645
it comes to meet.

342
00:16:36,645 --> 00:16:39,992
What we don't have
is a :: route.

343
00:16:39,992 --> 00:16:42,179
We don't have a default route.

344
00:16:42,179 --> 00:16:43,589
And again, this
sort of goes back

345
00:16:43,589 --> 00:16:45,415
to the fact that
this is a router,

346
00:16:45,415 --> 00:16:48,264
not a client. And it's
basically sitting there going,

347
00:16:48,264 --> 00:16:49,269
I'm a router.

348
00:16:49,269 --> 00:16:51,283
I should have routes.

349
00:16:51,283 --> 00:16:52,276
I'm not client.

350
00:16:52,276 --> 00:16:54,777
I don't just go to
the default route.

351
00:16:54,777 --> 00:16:56,897
But if you want
it to, going back

352
00:16:56,897 --> 00:16:58,189
up to our command where we put

353
00:16:58,189 --> 00:17:01,382
the address in, auto-config,

354
00:17:01,382 --> 00:17:03,290
there's another
choice on this which

355
00:17:03,290 --> 00:17:07,843
is to add default to it and
actually get a default route.

356
00:17:07,843 --> 00:17:12,139
If we do that, then
it will insert

357
00:17:12,139 --> 00:17:14,966
the default route into
the routing table.

358
00:17:14,966 --> 00:17:18,181
Let's give it a second here.

359
00:17:18,181 --> 00:17:19,709
We may have to
actually bounce the

360
00:17:19,709 --> 00:17:21,150
interface to get
it to do it again.

361
00:17:21,150 --> 00:17:22,457
Now there we go.

362
00:17:22,457 --> 00:17:24,959
Usually it kicks in, but I'm not

363
00:17:24,959 --> 00:17:27,027
patient so I often
just bounce the

364
00:17:27,027 --> 00:17:28,309
interface quick.

365
00:17:28,309 --> 00:17:33,964
There we go. There's your ::/0,
otherwise known as a default.

366
00:17:33,964 --> 00:17:36,561
It is from neighbor discovery.

367
00:17:36,561 --> 00:17:40,082
That is your ND default,
neighbor discovery default.

368
00:17:40,082 --> 00:17:44,130
By the way, also notice
that it gives it a very,

369
00:17:44,130 --> 00:17:49,008
very good admin distance,
and of course,

370
00:17:49,008 --> 00:17:51,268
the metric is 0 because
it's conneted.

371
00:17:51,268 --> 00:17:52,156
These are going to be

372
00:17:52,156 --> 00:17:54,126
really very believable
routes when

373
00:17:54,126 --> 00:17:59,367
it comes to comparing this
to other routing protocols.

374
00:17:59,367 --> 00:18:01,678
What we don't have at this point

375
00:18:01,678 --> 00:18:08,810
is if I said do show
ipv6 dhcp interface

376
00:18:08,810 --> 00:18:17,744
gigabit 00.36 is-- we're not
getting this from DHCP.

377
00:18:17,744 --> 00:18:19,216
In a couple of minutes, this is

378
00:18:19,216 --> 00:18:21,824
going to change a
little bit in our

379
00:18:21,824 --> 00:18:26,057
next lesson. For right now,
that's it, that SLAAC.

380
00:18:26,057 --> 00:18:27,728
It's pretty straightforward.

381
00:18:27,728 --> 00:18:34,184
The big thing to remember, of
course, is that it's not DHCP.

382
00:18:34,184 --> 00:18:37,699
All you're getting is
a prefix, a prefix

383
00:18:37,711 --> 00:18:40,635
length, and your
default gateway.

384
00:18:40,635 --> 00:18:43,828
The host portion, you
make up yourself,

385
00:18:43,828 --> 00:18:46,489
and as far as any other options

386
00:18:46,489 --> 00:18:50,206
that you would normally get from
DHCP, then this is not going to

387
00:18:50,206 --> 00:18:52,011
give you those options.

388
00:18:52,011 --> 00:18:57,370
[music]