So now that we have our BGP adjacency, our neighborship set up with external B
GP,
it's now time to go ahead and start advertising some routes. So let's start off
with tier zero
and specify that this gateway, their tier zero gateway should advertise. Let's
go ahead and
advertise the routes here for the 1010 zero network and also the routes over on
this segment,
which is the 1020. Now currently we're advertising those via OSPF. And what I
like to do is now change
that and modify it so we're advertising those same networks, but this time
through BGP. And
because we have our BGP, the partnership here between this external BGP speaker WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
because we have our BGP, the partnership here between this external BGP speaker
,
that's a fancy way of saying a BGP router and our tier zero gateway. If we
start advertising
these two subnets via BGP, those routes should show up right here on our BGP
router. So that's
what we get to do right now. Now as part of that too, on this Cisco router,
this currently running BGP,
let me go ahead and hit the upper key just to confirm we're not learning any
routes yet from
our peers. And that's the dot 61 edge one and dot 62 edge to, and I'm going to
use a command called
debug and I'm going to do a debug IP routing. Now the benefit of doing this WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
debug and I'm going to do a debug IP routing. Now the benefit of doing this
debug IP routing is
that anytime on this Cisco multi layer switch anytime the routing tables change
for IP version four,
we're going to have messages that indicate that that's happening. And that's
going to be near real
time. So I'm going to leave that debugging on so that once we start advertising
routes,
it'll be very obvious that those routes are showing up here on this multi layer
switch. So
if we do this as show IP route and press enter currently, currently I don't
have a whole bunch
of routes on this device. I've got a default route. It's a static route. And I WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
of routes on this device. I've got a default route. It's a static route. And I
've got a directly
connected network of 192, 160, one zero with the IP address of 121. But I don't
have on this Cisco
router any routes for 10 10 or 10 20 yet also take a moment and go back to our
VRF for a services
router. And we do a get BGP neighbor summary. Currently it's still showing that
we're not
advertising any prefixes or networks out to that neighbor. So let's change that
by going to the
networking tab up on top under connectivity clicking on tier zero gateways. And WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
networking tab up on top under connectivity clicking on tier zero gateways. And
let's edit the details
of our tier zero gateway. So we'll click on the three dots from the menu, we'll
click on edit,
and then we'll scroll down. And currently we're doing a route redistribution.
And that's right
down here. We did it previously with OSPF. So what we could do is we could just
modify what
we're redistributing and how we're redistributing those routes. And so to do
that, I'm going to click
right here on the route redistribution where it shows one. And currently we're
redistributing the
subnet 10 and subnet 20 via OSPF. And we want to modify that, click on the
three dots,
click on edit, and say, you know what, instead of doing it via OSPF, let's do WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
click on edit, and say, you know what, instead of doing it via OSPF, let's do
it via BGP. So now
we're going to be redistributing via BGP. And as far as what we're redistribut
ing,
let's click right here on this one and just confirm what we're going to redist
ribute. So this effectively
says take any of your tier one subnets, which in our topology are the 10 10
network and the 10 20
network and redistribute them or advertise them via BGP. So with this in mind,
we'll click on apply,
we'll click on add here, we'll click on apply here, and then we'll click on WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we'll click on add here, we'll click on apply here, and then we'll click on
save, and we'll scroll down,
click on close. And now that we're advertising or supposedly advertising the 10
10 and 10 20 subnets
via BGP, let's go back here to our external BGP router, which has debugging
enabled. And this is
verify whether or not we see those console messages about those routes showing
up. So here we are back
at our router and sure enough, here we have console messages saying, hey,
updating BGP 10 10 zero,
the 24 bit network via the next top at 192 once you date 1.61. And that's our
edge transport node edge WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
edge transport node edge
one. We also have an update regarding the 10 20 network that we've learned
about via BGP with
the next top of 192 once state one dot 61. So now we hit the upper key a couple
times into show IP
BGP summary is showing us that we have those two neighbors still and we've
learned two prefixes
or two networks from each of them. So in the case that we're learning the same
routes, in this case,
is the 10 10 and 10 20 networks, and we're learning it, the router 673 is
learning it from both edge
one and edge two, which one of those routes is it going to use? And we can see
the details for that WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the details for that
on the Cisco device by doing a show IP BGP space in the question mark, and I'm
gonna say IP V4
space and the question mark, unicast, the fancy way of saying please show me
the BGP table for
IP V4 on this is good advice. So here what is showing it on the far left, we
have the asterisk,
which means is the valid route. And then furthermore, we have a little greater
than some more right here.
That means it's the best route. So what that says is this route to the 10 10
zero network is the
best route through dot 61. And this route right here to the 10 20 zero network WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
best route through dot 61. And this route right here to the 10 20 zero network
with the next top of
192 once state one 61 is the best route. I also have my debugging still enabled
. Let me turn that off
with an undibug all and let me have the up here a couple times. Let's take a
look at the routes
again. So what's happening is edge one, which is the active device in our
active standby pair.
It's advertising a path of 777 meaning this route came from a ton of system 777
. And the other router
dot 62, which is edge two pre-pended that same autonomous system three more
times just to make
it look worse. And that way, as we receive those routes, we'll say, Hey, you WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
it look worse. And that way, as we receive those routes, we'll say, Hey, you
know what, I've got
the same route from these two peers, I'm going to choose the one that has the
least number of
autonomous systems they had to cross through. And that's why right here, we're
using this is our
best route coming from edge one. And the other routes going from edge two are
not considered as
good because they have a longer as path. So right here from this multi layer
switch, if we did a ping
to 10 dot 10 dot zero dot 10. And let me also make sure that is up and running.
So that's this
little VM right here, 10 10 zero 10, because we now have reach a billion WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
little VM right here, 10 10 zero 10, because we now have reach a billion
routing information on this
BGP speaker, we should be able to forward traffic and have it routed down to
that little VM. So let's
verify that by bringing a little terminal window. This is a VM number one. And
if we do a ping to 192
dot 168 dot 1 dot 121, that should work fantastic. We should also be able to
ping from here from the
external BGP router down to 10 10 0 10. So put some there and that's working
great.