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So IPv6 IP tunnels.

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Now, there are subtypes of this

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that we'll see in
the next lessons

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coming up. But this
is just straight

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point-to-point manual
IPv6 IP tunnel.

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We're going to use the

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same topology we used
in our last lesson.

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 So as a reminder,

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we have a tunnel between R1
and R4 that's already built.

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We're not going to rebuild that.

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We're already running
EIGRP across it,

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and we're already
exchanging routes.

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So just to follow-up with this,

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we'll switch over to
the command line.

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Here's our tunnel,
and it's currently

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running Protocol Transport,

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GRE IP. Again, this will
be very, very short,

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because now all we do is say,

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tunnel mode ipv6ip
on both sides.

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And what this is going
to do is tunnel goes

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down and it comes right back up.

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What this did is get
rid of the GRE header.

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So if we look at
our tunnel again,

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first off, where this said total
protocol transport is GRE,

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tunnel protocol transport
is now IPv6 over IP.

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So what this just
did is this just

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limited us to only being able

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to carry IPv6.

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That's all. What it
buys us is, number one,

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the ability to run some of our

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upcoming tunneling
options that we're

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going to take a look
at - that's one thing.

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The other thing
it does for us is

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allows us to save--
it's not like

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it's a ton, but 1476 was our MTU
up here and now our MTU is 1480.

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So we're saving four
bytes on the GRE header.

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It's not really a huge deal.

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Honestly, the biggest
reason to go

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to IPv6 IP is to enable some of

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the dynamic tunnels that we're

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going to take a look at next,

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such as the 6-4 tunnels
and the ISATAP

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tunnels which are going to take

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a little bit more of building.

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What we’re going to do for those

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is we're actually
going to do some

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static routes, and
then we're going

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to also redo our tunnel when

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we get to that section.

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That's really it.

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To go from GRE to IPv6 IP,

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it's literally just typing
in that one command.

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You save four bytes of overhead,
but more importantly,

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we need to do this as we
move into our next options.

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