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So IPv6 IP tunnels.
Now, there are subtypes of this
that we'll see in the next lessons
coming up. But this is just straight
point-to-point manual IPv6 IP tunnel.
We're going to use the
same topology we used in our last lesson.
So as a reminder,
we have a tunnel between R1 and R4 that's already built.
We're not going to rebuild that.
We're already running EIGRP across it,
and we're already exchanging routes.
So just to follow-up with this,
we'll switch over to the command line.
Here's our tunnel, and it's currently
running Protocol Transport,
GRE IP. Again, this will be very, very short,
because now all we do is say,
tunnel mode ipv6ip on both sides.
And what this is going to do is tunnel goes
down and it comes right back up.
What this did is get rid of the GRE header.
So if we look at our tunnel again,
first off, where this said total protocol transport is GRE,
tunnel protocol transport is now IPv6 over IP.
So what this just did is this just
limited us to only being able
to carry IPv6.
That's all. What it buys us is, number one,
the ability to run some of our
upcoming tunneling options that we're
going to take a look at - that's one thing.
The other thing it does for us is
allows us to save-- it's not like
it's a ton, but 1476 was our MTU up here and now our MTU is 1480.
So we're saving four bytes on the GRE header.
It's not really a huge deal.
Honestly, the biggest reason to go
to IPv6 IP is to enable some of
the dynamic tunnels that we're
going to take a look at next,
such as the 6-4 tunnels and the ISATAP
tunnels which are going to take
a little bit more of building.
What we’re going to do for those
is we're actually going to do some
static routes, and then we're going
to also redo our tunnel when
we get to that section.
That's really it.
To go from GRE to IPv6 IP,
it's literally just typing in that one command.
You save four bytes of overhead, but more importantly,
we need to do this as we move into our next options.
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