- [Instructor] In our previous video
we configured multiprotocol BGP.
In other words, we could use BGP to advertise
both IP version four and IP version six networks.
And in the previous video,
we advertised both types of networks
over an IP version four session.
Remember, there's a TCP session
that gets set up between our BGP neighbors,
well, we just had one session,
it was an IP version four session,
where we pointed to our neighbors IP version four address
and over that session,
we advertised both IPv4 and IPv46 networks.
The challenge we had though in the previous video
was that when I advertised an IP version six network
to my neighbor, it would not know how to get back to me.
It did not know my IP version six address,
it didn't know the next hop in other words.
To fix that, we created a route map.
And the route map said, "I am the next hop."
And we stuck on that next hop attribute
on all of the IPv6 route advertisements
we were sending to our neighbor.
And that was sort of a workaround
but there's another way to configure it.
And that's what we're going to do in this video.
Instead of having all of our advertisements
go over an IP version four session,
we're going to have two sessions.
We're going to have an IP version four session
that advertises IP version four networks,
and we're going to have an IP version six session
over which we're going to be advertising
IP version six networks.
The downside is we've got more neighbor ships,
one for IPv4 and one for IPv46.
The upside is we don't have to configure
the route map any longer.
So it's up to you, it's a design decision,
but I wanted to give you both options.
Let's remind ourselves of how things
are configured currently on Router::R3,
let's do a show run pipe to section router bgp.
And we had a couple of address families,
we had one for IP version four and one IP version six,
but for this IP version six address family
notice our neighbor,
we're pointing to the IP version four address
of our neighbor.
And that's the reason that we needed to reference
the route map to say,
"Hey, we're the next hop."
If you want to get to any IPv46 networks
that I advertised to you.
Let's fix that.
Let's go in to router configuration mode
for BGP Autonomous System 65,001,
and I want to create a new neighbor.
I'll say "neighbor" and I'm going to point to the IPv46 address
of my neighbor, which is 2000:2::2.
It's in a remote autonomous system of 65,004.
Now, let's go into our IPv46 address family.
I'll say address-family IPv46.
And we'll say "no, neighbor 198.51.100.6"
And that should get rid of both of those commands.
In fact, let's confirm that,
let's do a do show run pipe to section router bgp.
And it didn't get rid of my neighbor commands
under the IPv46 address family,
but unfortunately, that command I just issued,
it also got rid of my neighbor statement up here.
So we need to fix that,
we need to put our IP version four neighbor back.
We want these two sessions I'll say,
"neighbor", and our neighbors address is 198.51.100.6,
and it's at a remote autonomous system of 65,004.
Now, let's go into the address family configuration mode,
for IPv46, we'll say "address-family ipv46",
and I need to activate that neighbor.
I don't need to say here's a route map
because we don't need that any longer,
but I do need to activate the neighbor.
I want to say "neighbor 2000:2::2 activate".
Now let's remind ourselves how things look now.
Let's do a do show run pipe to section router bgp.
Notice that we have two neighbors statements,
one for IP version four, and one for IP version six.
The IP version four address family automatically goes active
when we specify a neighboring IPv4 address,
and we had to manually activate our neighbor
under the IPv46 address family,
but there's no route map here.
Now let's go over and give a mirror configuration
on ISP Two.
On ISP Two, let's go into router bgp
for Autonomous System 65,004,
and let's specify an IPv46 neighbor.
I'll say "neighbor 2000:2::1" and that neighbor,
which is R3 is in a remote autonomous system
of 65,001.
Now, let's go into our address family,
for IPv46, let's get rid of those neighbor statements.
We'll say "no neighbor 198.51.100.5",
and that cleaned up our IPv46 address family,
but remember, it had the unintended side effect
of getting rid of our neighbor statement
under BGP configuration mode.
So I'm going to back up one level, and I'm going to say,
"neighbor 198.51.100.5",
and it's in remote autonomous system of 65,001.
Now let's just make sure that things look
as we think they do,
let's do a do show run pipe to section router bgp.
We do have two neighbor statements,
one for IPv4, one for IPv46, excellent.
For the IPv4 address family, were activated
and that happens automatically for our neighbor.
And for the IPv46 address family, that's what we need to do,
we need to activate our IPv46 neighbor.
So let's go into address family
configuration mode for IPv46,
and we're going to say, "neighbor 2000:2::1 activate".
And that should bring up our IPv46 neighbor ship.
We've now got two adjacencies.
We've got an IPv4 adjacency
and we've got an IPv46 adjacency.
Let's confirm that we're exchanging
both IPv4 and IPv46 routes.
Let's do a show ip route to see our IP version four routes.
Am I learning anything via BGP?
I am, just as we saw in our previous video,
I'm learning about the 10.1.1.0 network
that's being advertised by R3.
What about IPv46 networks?
Let's do a show ipv46 route,
and I'm learning about the loopback address on Router::R3
specifically loopback one,
it's part of the 2000:1::/64 network.
If I want to see the BGP topology table for IP version four,
I can do a show ip bgp,
and these are the IPv4 networks in our topology table.
If I want to see the IPv46 networks known to BGP,
I can do a show bgp ipv46 unicast command.
And this shows the IPv46 networks that were aware of.
We're directly connected to this network,
but we learned this network via BGP.
And here we see the next hop,
we didn't specify the next hop with a route map here,
we got rid of that statement,
but it was learned automatically
because now we have two sessions,
one for IPv4 and one for IPv46.