Our mission should we choose to accept it is to go ahead and configure this
autonomous system,
a autonomous system 20 with the IBGP nameorship and the two external BGP name
orships as shown,
and then advertise R22's loopback so that it's advertised via BGP. So we're
going to start off by
going to R21 and R22, we'll remove the existing config, and then we'll follow
these steps and
put it all back. With that being said, let's make a road trip over to the lab
environment. So here in
the lab environment, let's go to R21, let's just look at our topology real WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
the lab environment, let's go to R21, let's just look at our topology real
quick. Here it is,
let's double click on that to open it up. All right, so let's go up to R21 and
R22. In fact,
we can remove the configurations just by going to this icon right here, the
carriage return icon,
and from there, we'll do a config T and no router, BGP, autonomous system 20,
and end, and that should
do it. So we must then enter R21 and R22. I'll select those two routers, click
on send script, and
it is done. So all those routers, if we did a show, run, section, BGP, not BGT,
but BGP. There is WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
but BGP. There is
no configuration for BGP whatsoever. So the first step is done. We've removed
the configuration for
BGP from both R21 and R22. So let's go back to R21 and begin our config. So we
'll go into configuration
mode. We'll type in router, BGP, autonomous system 20, and our neighbor, I'm
going to point
to the loop back address at 22.22.22.22 and say, remote, autonomous system,
same as ours, which is 20,
and I'll hit the up arrow key and say, update source, loop back zero. Also, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and I'll hit the up arrow key and say, update source, loop back zero. Also,
while I'm here, I'm going to say
that neighbor 22, 22, etc. that I was supposed to add next top self as I
learned routes from other
external neighbors and I send them to this internal BGP neighbor. I'll set that
next top to my address.
All right, so that's our internal neighbor. And while we're here, let's also go
ahead and do the
external neighbors as well. So we're going to neighbor with R11 at 23.10.20.11
and we're going to neighbor
with R42 at 23.20.40.42. And for each of the routers, you can either go look at WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
with R42 at 23.20.40.42. And for each of the routers, you can either go look at
the IP addresses on
those interfaces or just realize that the last octet on every router matches
its router number.
So let's configure the external BGP neighbor ship between R21 and R11. So we'll
say neighbor and
R11 address is 23.10.20.11 and the remote AS that they're in is 10. That's R11.
And I'm just going
to pause here for a second because R11 is already configured. And so it should
give me a console message
in just a moment. There it is that that neighbor ship is up. Then we'll do WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
in just a moment. There it is that that neighbor ship is up. Then we'll do
another neighbor statement
for 23. We want to go down to R42, which is at 23.20.40.42. And that's in the
remote autonomous system
of 40. So we'll put that in. Oh, look at all those characters. I have like a
five octet IP address.
So it's 23. I have one to many 23s in there. So let me go ahead and fix that up
. Neighbor 23.20.40.42
in press center much better. And we'll verify that the neighbor comes up as WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
in press center much better. And we'll verify that the neighbor comes up as
well. Fantastic. So then
that we have that done. Let's go ahead and go configure R22. So R22 is right
here. So we'll go into
configuration mode and type in router, BGP. And we're in a system 20. And our
neighbor is going to be
21.21.21.21.21.21. And the remote AS is the same as ours, which is 20. And we
're going to say
for that neighbor, we want our update source to be loop back zero. And if you
use the actual physical
interface on that directly connected network, you wouldn't need to worry about
doing the update source. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
doing the update source.
So I'm going to go ahead and do that. And then on both router 21 and 22, I'm
going to do a clear IP BGP
asterisk. And it is the same thing on router 21 to clear IP BGP asterisk. And
that's going to give us
a nice fresh establishment of our sessions and also a nice fresh update of all
the routes. And
again, it may take a moment or two for that to fully converge. So while it's
happening, we need to show
IP BGP summary. And that wasn't too bad. So we have three routes that we've
learned from R11. And WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
learned from R11. And
we also have three routes that we've learned from router 42. And we haven't
learned any routes yet
from R22. And that's because we have not yet advertised any routes. So if we do
a show IP BGP,
that'll show us the routes that we've learned in the rib. And at the moment, we
don't have any greater
than symbols, but that will rectify itself here in a moment once R21 decides.
So while it's still
thinking about that, let's go to R22. And let's advertise our loop back address
with a show IP
interface brief, verify what our loop back address is. And the IP address is a WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
interface brief, verify what our loop back address is. And the IP address is a
32 bit one who do a show
IP route, a little confirm it for us. So there it is right there. It's a 32 bit
route. So we're going to
configuration mode router, BGP, autonomous system 20, all type in network 22.22
.22.22.22 space the keyword
mask, and then the 32 bit mask, beautiful type in end. And that's a show IP BGP
press center. And there
are all the routes. So that's the route that we just added on our 22. That's
why the next top is
0, 0, 0, 0. And then we have the routes for the 12, 12, 12. That's the loop WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
0, 0, 0, 0. And then we have the routes for the 12, 12, 12. That's the loop
back on R12. We have the
route for router 32. And we have the route sourced by router 43. So now here
from router 22, we should be
able to ping those other respective loop backs sourcing it from our loop back
because they also have
reachability back to us. And let's test that next. So in R22, let's go ahead
and do a ping over to
how about let's go down to R32, which is 32.32.32.32.32. And I got excited that WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
how about let's go down to R32, which is 32.32.32.32.32. And I got excited that
I forgot to say,
hey, source this from my loop back zeros. So we're sourcing this from the IP
address on our gig 1/0
interface here on R22. And what I need to do is do a source it from loop back
zero, which is the
22 22 22 to address. And because the destination R32 has a route back to our
loop back at 22 22, etc,
we should be able to get a response. And that looks much better. It's also a
trace and verify the
path. So we'll do a trace route to 32.32.32.32.32.32.32 and we'll source it
from loop back zero.
And if you just take a peek just for a moment at the edge router R21 and we do WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And if you just take a peek just for a moment at the edge router R21 and we do
a show IP BGP, as we
try to go to 32, its preferred route is using the next top of 23.10.20.11,
which is R11. So after
the packet goes to R21, the next hop in the path should be R11. We can verify
that by doing the trace.
So do the trace and sure enough, the first top is R21 and the next top is R11,
then to R31, then finally
to R32. And if you just show IP BGP summary, that'll show us who our neighbors WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
to R32. And if you just show IP BGP summary, that'll show us who our neighbors
are and how many
prefixes we've learned from that neighbor. And if you just show IP BGP enter,
it'll show us the
BGP rib, the routing information base with all the routes that we know about.
And for the routes
in the routing table, we can just show IP route. We can also show IP route
followed by BGP, just to
narrow it down to the BGP learned routes in the routing table. So thanks for
joining me in this
fundamental look at the world of BGP, where we had an opportunity to look at
and configure and
verify internal BGP, external BGP. And if you're interested in even more and WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
verify internal BGP, external BGP. And if you're interested in even more and
more detail on BGP,
which there's a lot more detail to it, come see us in one of our additional
professional level
courses for Cisco, such as an RC, which provides an even deeper look and goes
into more of the
methodologies and options in tweaking and tuning BGP. But for now, thanks for
joining me in this set
of videos. And I look forward to seeing you in another set very, very soon. And
until then,
I hope this has been informative and I'd like to thank you for viewing.