In this video, we're going to focus on internal BGP.
That's IBGP for short.
And that basically means that the two ends of our BGP
session, the two routers that are participating in BGP,
are both in the same autonomous system number.
And the syntax is really simple.
We go into configuration mode and then from configuration mode,
we type in router, space, BGP, space,
and then our local autonomous system number.
So in this case, that pair for a autonomous system 10,
we put a 10, and then we press enter.
And that puts us into router configuration mode for BGP WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And that puts us into router configuration mode for BGP
autonomous system number 10.
And then from there, what we would do
is simply specify who our neighbors are.
So the syntax would be neighbor.
And then the address of that neighbor, B, C, D,
in the case here of R12, we could point the loop back.
And on the loop backs are the same as the router number.
So R12 has a loop back of 12, 12, 12, 12.
R13 has a loop back of 13, 13, 13, 13, 13.
R11 has a loop back of 11, 11, 11, 11, and so forth.
And within an autonomous system, I've already
got OSPF running, already advertising those loop backs. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
got OSPF running, already advertising those loop backs.
So all the loop backs here in a autonomous system 10
are reachable to other devices in the same autonomous system,
same thing over here in AS20 and AS30 and inside of AS40.
So we'd say neighbor, space, if we want to point to a loop
back address of our peer we can, and then space,
then we're going to use the command remote, dash AS.
Now, even if our peers in the same autonomous system,
that's the keyword, remote, dash AS in the space.
And then we specify the AS number of 10.
So we'd use this command on our 12, our 13, and our 11 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we'd use this command on our 12, our 13, and our 11
as we peer with each other to their loop backs.
Now, if we are peering to the loop backs,
we need to one of their statement that is neighbor,
same neighbor IP address, space, and we use the command
update source, and then loop back zero, if that's the IP address.
And that way, when we start our session, for example,
from our 12 or our 13, we'll be sourcing it from loop back zero.
And if we target 13.13.13.13.13, then we're
specifying the correct IP address for the peering on both sides.
The loop back zero here, we're going to loop back over here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
The loop back zero here, we're going to loop back over here.
So in order to source it from our loop back, instead of just
the interface, from a routing table closest to that destination,
we want to use that update source command,
and specify the source IP address.
In this case, the interface associated
with the source IP address, we want that session to begin from.
And when we reach out and we start the session,
we're going to be using TCP.
And the destination port is 179.
So part 12 was starting the session.
So we would use some high numbered unused port at the moment,
and connect over to our 13 at port 179. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and connect over to our 13 at port 179.
And they can both use that session as they negotiate
and set up their BGP neighborship.
But the destination well known port for BGP
is TCP port 179.
So if we wanted to configure this autonomous system
in the IBGP neighborships, we'd basically
do this configuration on a routers 12, 13, and 11.
And we would point, for example, in our 12,
we'd point to the loop back address on our 12 for the peering.
And from our 12, we'd point to the loop back address of our 11
and vice versa.
From our 11, we'd point to the loop back over on our 12.
And from our 11, we'd point to the loop back over here WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And from our 11, we'd point to the loop back over here
on our 13.
So with that in mind, let me go ahead and walk you
through sitting up the IBGP neighborships
here between our 11, our 12, and our 13.
So let me bring up the topology here,
just to confirm our topology looks good.
And we're going to be focusing on AS10.
So let me go ahead and double click here on server 1
and hug, bring it up, give that a moment to initialize.
There it is.
Fantastic.
And here's tabs for all of the routers.
So currently in our 11, our 12 and our 13, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So currently in our 11, our 12 and our 13,
I believe BGP has already configured.
So if we do a show, IP protocols and press center, sure enough.
I've got here, I've got OSPF running.
That's great.
And if we hit the space bar, I've got BGP already running.
So I'm going to remove BGP from our 11, our 12 and our 13.
So we can demonstrate the entire configuration of the IBGP
neighborships from scratch.
So I'm going to use this icon right here,
the little carriage return icon right below the help.
And click on that.
And we're going to go into configuration mode WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we're going to go into configuration mode
on all three routers, and do a no, router, BGP,
and a ton of system 10, and type in end.
And we're going to apply that to our 11, our 12 and our 13.
And we'll click on send script.
And it is done.
We've just removed BGP.
So now we do a show, IP protocols, press center.
I've got OSPF.
If we hit the space bar, but we don't have BGP running anymore.
All right, so let's start on our 11.
Now we want to peer from our 11, we want to peer with our 12, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Now we want to peer from our 11, we want to peer with our 12,
at our 12's loopback of 12, 12, 12, et cetera.
And we also want to peer from our 11 with our 13,
at its loopback of 13, 13, 13, 13.
And so we can verify, first of all,
those routes from the routing table do a show IP route, press center,
and sure enough, there's 12, 12, 12, 12, and 13, 13, 13,
13, both in the routing table.
Because if we can't reach those loopback addresses,
you're not getting me able to peer to those IP addresses with BGP.
So we're relying on the interior, get me a routing
for a call, in this case, OSPF, for reachability to those loop WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
for a call, in this case, OSPF, for reachability to those loop
backs.
So here in our 11, we'll go into configuration mode.
We'll type in router, BGP.
And we want to use a ton of system 10, press enter.
And then we'll specify our first neighbor.
Let's go ahead and use our 12.
So we'll type in neighbor.
And I'm going to go ahead and just copy and paste the 12, 12, 12,
12 from right here.
And then the keyword remote AS.
And then R12 is also in a ton of system 10.
So even though the keyword is remote, dash AS,
think of it like what AS is the remote device in.
It's also in 10.
And so effectively, once we're done configuring the other side WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And so effectively, once we're done configuring the other side
as well, R12, it's going to configure an internal BGP
neighbor ship, because both routers are 11 and 12
are both in the same ton of system.
Now because I'm going to be sourcing it,
I want to source it from my loop back address,
going to their loop back address.
I'm going to hit the upper of key into a neighbor 12, 12, 12, 12 again,
and specify update source loop back zero, just like that.
And then I'll do the same process for R13.
So if you look at our topology, R13 is in the top of a ton of system 10.
And we're going to pair to it at its loop back address of 13, 13, 13, etc. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we're going to pair to it at its loop back address of 13, 13, 13, etc.
So we'll type in neighbor, 13.13.13.13.13.
And that's also in the same AS, we'll do remote AS 10 enter.
And then we want to go ahead and specify for that neighbor
that we want to use our update source of loop back zero, just like that.
And we'll do a do show run section router.
And here's our BGP configuration for BGP, a ton of system 10.
We have two peers at 12, 12, etc., and 13, 13.
And we've also specified that for those purings,
we want to use our own local loop back zero address, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we want to use our own local loop back zero address,
which on R11 is 11, 11, 11, 11.
All right, so next, let's head over to R12.
So here at R12, we'll do a similar treatment.
We'll go into configuration mode, router, BGP, a ton of system 10.
And we'll specify that we have a neighbor, or we want to have a neighbor,
over at 11.11.11.11.
And the remote AS is 10.
And for that same neighbor, we want to use update source loop back zero.
And then similar treatment for 13, 13, 13, 13.
We also just got an up notification at the console,
regarding that neighbor ship, fantastic. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
regarding that neighbor ship, fantastic.
So we'll do a neighbor for 13.13.13.13.13.
Remote AS 10, and also update source using our local loop back zero.
So we do a show run, right, section router.
Take a look at that.
Here's our configuration for BGP, a ton of system 10,
that we just configured on R12.
So next, we'll go to R13 and do something extremely similar,
except we'll point to the IP addresses of R11 and R12's loop back zero
addresses for those purings.
So we'll go to R13 and FIGT, Router, BGP, 10. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we'll go to R13 and FIGT, Router, BGP, 10.
Neighbor is going to be 11.11.11.11 in the remote autonomous system of 10,
same as ours, that makes it an IBGP peer.
And for that neighbor, we want to use update source loop back zero.
And then neighbor 12.12.12.12, remote autonomous system 10, same as ours.
It'll be an IBGP neighbor ship.
And for that same neighbor, we want to use update source loop back zero.
And we'll do a show run, pipe section router.
Actually, it's to pipe section BGP, press enter, that'll work even better. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Actually, it's to pipe section BGP, press enter, that'll work even better.
So there's our BGP configuration that we just configured on R13.
Now, in a production environment, you wouldn't want to do a full reset of BGP
because BGP is fairly slow to convert, and it may take a while.
However, in this case, in a lab environment, it won't be too bad.
So let's go ahead and hit the character trunite icon up here.
And I'm going to do a clear IP BGP asterisk.
Now, in a production environment, with hundreds of thousands of routes,
this is a really bad idea. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
this is a really bad idea.
You want to do a soft reset.
But this is a hard reset.
We'll do a clear IP BGP and press enter.
And we'll apply that to R11, R12 and R13.
Click on send script, and it is done.
So just be aware that after you do a clear IP BGP asterisk,
it may take up to 60 seconds, or it may be even a little longer
for them to fully become adjacent and share any routing information
and provide all the updates.
So if we go to R11 in our topology, and in our topology,
that's this guy right here at the edge of a time system 10. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
that's this guy right here at the edge of a time system 10.
And so go ahead and do a show.
Oh, this guy didn't get a clear because he was in configuration mode.
Let me take a look at 12 and 13.
Oh, they did.
So because everybody else forced a clear, we're good to go as well.
So R11, if you do a show, IP BGP summary, which is a great command, press enter
,
is showing us that we have two neighbors, one at 12, 12, 12, 12.
That's the identity of that neighbor.
And the way that BGP chooses a router ID is exactly the same as it does for OSP
F.
If you've got one hard configured, it's going to use that. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
If you've got one hard configured, it's going to use that.
If you don't have one hard configured, it's then going to use the highest IP
address
on a loopback interface.
And if you don't have any IP addresses on loopbacks, it's then going to use the
highest IP
address on any other active interface at the time BGP comes up.
So for the lab, it's going to match the actual loopback zero address because we
're not
configuring manually the router ID, but we do have those loopbacks.
And that's why the ring used as the router ID.
So here we have those two neighbors.
Great.
We haven't received or on the far right hand side.
We haven't received any networks yet. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We haven't received any networks yet.
We do have the neighborships.
And we also can do a show IP, BGP, and press enter.
And that will show us any BGP routes from the routing information base.
And again, we haven't been advertising any yet.
So we shouldn't see any.
And we can also show IP, BGP, neighbors, press enter.
So here's the command show IP, BGP, neighbors.
It's showing us details about that neighbor, including the neighbor ID.
What AS it's in.
Well, version of BGP is running.
The current state, which is established.
It's going to be a question up further over two minutes.
And some of the capabilities regarding that BGP speaker.
And then if we scroll down, it has some stats. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And then if we scroll down, it has some stats.
We're getting sent and received.
And if we continue to scroll down by default, BGP4 is supporting IPv4 unicast.
And if we scroll down far enough, we'll get information on our next peer.
And here it is right here.
That neighbor is 13, 13, 13, etc.
And as we continue to scroll down, it has neighbor capabilities.
And other stats we're getting sent and received for that peer.
All right.
Fantastic.
We have AS 10 and the internal BGP neighborship setup between our 12, our 13
and our 11.
In the next video, let's turn our attention to setting up external BGP WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
In the next video, let's turn our attention to setting up external BGP
neighborships between
our 11 and its 2B neighbor, our 21 and also our 31, which are an AS 20 and AS
30 respectively.