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[AUDIO LOGO]

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So now that we've reviewed
how IPv6 addressing works

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and a little bit about
neighbor discovery,

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now let's jump onto
the command line

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and take a look at
what this actually

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looks like on the equipment.

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And we'll take a look
at a Wireshark capture

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and see what this actually looks
like on the network itself.

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So let's start by
looking at our topology.

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We're just going to be
looking at two routers,

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but we just want
to see who they're

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connected to so that the packets
make a little bit more sense.

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And then we'll jump into the
command line and Wireshark.

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So for this
demonstration, we will

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be using IS-IS IPv6 Topology 1.

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And again, in this
particular video,

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we're simply going to be
looking at IPv6 configuration

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and some good show
and debug commands.

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And we'll be
focusing on router 1.

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This way we get to see
some things on IOS XR.

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And then we'll also
take a look at router 5

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so we can see similar
outputs on IOS XE.

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So when we're
looking at router 1,

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we'll see things like
neighbor discovery

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from router 2, things like this.

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That's what we're going
to be looking for.

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So that said, let's go ahead
and jump into the command

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line on router 1.

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So we'll start off
here on router 1

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just by doing a show
ipv6 interface brief.

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And we can see here that all of
our interfaces that we're using

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in this lab are currently
configured both with

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a link-local address and with
a globally routable address,

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starting with 2001:db8.

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This is then followed
by the subnet portion,

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such as 10 or 12, 135,
167, and then, of course,

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followed by the host portion.

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Also, take note, as we discussed
during our addressing video,

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that all of these
interfaces have

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that same link-local address.

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And again, this is perfectly
fine and, quite honestly,

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a pretty convenient thing to do.

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We could also do a ping.

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So we'll ping out our Gigabit
0/0/0/0 interface and see if we

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can reach router 2.

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So for that, we'll ping the
globally reachable address.

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We'll ping the 2001::db8:12::2
would be router 2's host

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portion.

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We see here that
that's successful.

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That means that we also should
have done a neighbor discovery.

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So if we do a show
ipv6 neighbor,

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we should now have at
least router 2 as an entry.

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And we can see right
here that we do.

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Not only do we have
its global address,

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but we can see we have its
link-local address as well.

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Now, we can ping that
link-local address.

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But things do get a
little interesting.

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So if I say ping fe80::2, which
would be router 2's link-local

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address, the problem is
the router has no idea what

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interface to send that
out, because again,

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if we look at our
other interfaces,

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they all have fe80 on them.

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So we have to actually tell it.

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And here's the really fun part.

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If I say Gig 0/0/0/0 and hit
Enter, it's going to say,

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I don't know what that is.

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I've never heard of it.

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No, instead, what
you have to do is

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you have to actually
say GigabitEthernet

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and spell it out.

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Now you can see it
works perfectly fine.

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But just to show you one
other thing, if I do it again,

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it doesn't like that either.

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So not only do you have to
spell the entire interface out,

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but it has to be case sensitive.

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Now, I'm going to show
you one other thing that

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doesn't work here.

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And I know it might
seem odd to show you

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something that doesn't work.

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But you'll see why
in just a moment.

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If I say to ping fe80::2 and
then say %GigabitEthernet

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0/0/0/0, this is also
not going to work.

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The reason I'm bringing this
up is when we get to IOS XE,

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we will do this again.

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And we'll see that that
actually does work.

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This is a special
IPv6 naming convention

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that actually lets us list
the egress interface along

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with the destination.

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But as we can see, this
is at least currently

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not supported on IOS XR.

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Now, some other good
commands to look at--

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show ipv6 traffic brief.

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This will just give
us a general overview

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of how many packets have
been sent and received,

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and so on, as well as
ICMP statistics down here

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at the bottom.

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We can also see, when we
scroll down to the very bottom,

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that we have our
Neighbor Discovery ICMP

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statistics as well.

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So this is something that
we can keep track of.

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Of course, we can also
do show route ipv6.

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This will show us the
IPv6 routing table,

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which as of right
now is just going

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to be local and connected
routes because we haven't

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set up any routing just yet.

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And a good debug we
can keep track of

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is debug ipv6 neighbor
discovery packet.

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If we do this, we can see
here that we get a router

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advertisement message.

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So here we can see it would
show us all of our neighbor

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discovery packets.

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In this case, we just happen
to see a router advertisement

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message because these are
sent out on a timed basis.

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Of course, if we were
to ping something,

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we will be able to see
those neighbor discovery

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packets as well.

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But we'll see those in
our Wireshark capture.

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Now, let's jump over
to router 5 and see

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some of these similar
commands and how

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to see the same
information on IOS XE.

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So once again, we'll start with
a show ipv6 interface brief.

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Pretty much the same output.

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We can see once
again that we have

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both link-local and global
addresses on our interfaces.

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Now, on this one, notice, if
we do a ping fe80 colon colon--

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and let's again say we're
going to ping router 2--

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this is what we were
talking about earlier, where

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if I say percent, I can now
put the egress interface,

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GigabitEthernet2, and
it'll take this and use it

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as the egress interface.

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So we can see that this
convention works on IOS XE.

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It is, however, keep in
mind, still case sensitive.

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Once again, we have commands
like show ipv6 neighbor.

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This will show us our layer
2 to layer 3 mappings.

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We can see at this
point, all we've

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learned is router 2's
link-local address.

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If, by the way, we
were to change this

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and say ping router 4, which
is at that same segment,

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look at our neighbors again.

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We see that now we
know about 2 and 4.

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We still have the
show ipv6 traffic.

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Again, it shows us the
same basic information,

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slightly different output.

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Show ipv6 route--
again, just local

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and connected for right
now, but showing us the IPv6

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routing table nonetheless.

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And once again, we have
debug ipv6 neighbor discovery

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as a very useful command.

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On IOS XE, we'll have to turn on
terminal monitor to see those.

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And once again, we see a
router advertisement message

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coming in here--

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in this case, from router 2.

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So now that we've seen what this
looks like on the command line,

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let's jump into a
Wireshark capture.

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Now, this is a capture
I already made,

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so I'm just opening a presaved
capture, in this case.

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But let's take a
look at it because we

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can see both the router
advertisement messages as well

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as some neighbor discovery, both
solicitation and advertisement.

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So let's go ahead and jump
in and take a look at that.

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So this is our packet capture.

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It is filtered for
just IPv6 traffic.

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And what we see here on this
first packet here, number 12,

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is we have a router
advertisement message being

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sent from this MAC address.

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And it's going from
the source of fe80::2,

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which would indicate to us in
our design that that's router

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2.

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And it's going to the
destination ff02::1,

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which in IPv6 is a link-local
multicast for all routers.

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So in this case, this is router
2 announcing itself as a router

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onto the segment.

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And if we look down here
into the actual packet

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itself, under the Internet
Control Message Protocol

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version 6, two things we want
to look at that we've discussed.

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The first is the fact that this
is a type Router Advertisement,

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and it is in fact type 134.

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Also, what's it
actually advertising?

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It's advertising that it has
this prefix, 2001:db8:12::/64,

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as an available prefix
that it's routing for.

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So this is a router
advertisement message

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as it would look on the network.

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Our next packet, number 44, is
a neighbor solicitation message.

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In this case, we can see that
it's fe80::1, so router 1,

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looking for the
destination 2001:db8:12::2.

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What do we see
about this packet?

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So we can see that it's type
Neighbor Solicitation, which

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is type 135.

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And what's it
actually looking for?

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We can see that it's looking
for the target address,

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2001:db:12::2.

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So again, this is the
neighbor solicitation,

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much like an ARP request.

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Right below this, packet 45, we
have 2001:db:12::2 responding

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to fe80::1, which is router 1.

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And it's a neighbor
advertisement.

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This is the router responding
with its MAC address,

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saying that it has that address.

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We see here that under
the ICMPv6 option,

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it is replying with
its MAC address.

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So this would be the equivalent
of the ARP reply in IPv4.

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So in this video, we jumped
into the command line,

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and we took a look at
our IPv6 interfaces.

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We did some testing
with some pinging.

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We looked at some debugs for
the neighbor discovery packets.

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And then we jumped
into Wireshark,

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and we looked at what router
advertisements, neighbor

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solicitation, and neighbor
advertisement messages all

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look like on the network itself.

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I hope this has been
informative for you,

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and I'd like to thank
you for viewing.

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