Hello @lagapidis
Thank you so much for the reply. It is clear to me now 
Let’s suppose, there is no route reflector(R2) in the same topology. R2 is just like a ibgp neighbor.
In this case, does R4 and R5 exchange the ibgp routes to each other about the ip prefix 6.6.6.6/32.
On R4:
Can we see 2 BGP routes. one best path as ebgp and the other ibgp route via R5.
On R5:
Can we see 2 BGP routes. one best as ebgp route and the other ibgp route via R4.
Hello Moulali
If there is no route reflector in the topology, then iBGP requires that you have a full mesh iBGP neighbor peerings. That means that each iBGP router will receive BGP routes from all other iBGP routers. In this case, R4 should see the route to 6.6.6.6 via R5 and visa versa. But the eBGP path will be chosen as the “best” path to that destination in both cases.
So yes, what you describe in your post is correct.
I hope this has been helpful!
Laz
Hi. Rene, Lazaros, Staffs.
I have a question.
I tried verify about BGP Additional-paths on my lab.
But R6’s routing table don’t have entries about AS 12345 Network through BGP.
Is this correct?
R6#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 6.6.6.6/32 0.0.0.0 0 32768 i
R6#sh ip route
Gateway of last resort is not set
6.0.0.0/32 is subnetted, 1 subnets
C 6.6.6.6 is directly connected, Loopback0
192.168.46.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.46.0/24 is directly connected, GigabitEthernet0/1
L 192.168.46.6/32 is directly connected, GigabitEthernet0/1
192.168.56.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.56.0/24 is directly connected, GigabitEthernet0/2
L 192.168.56.6/32 is directly connected, GigabitEthernet0/2
R6#
Hello Yoichi
Yes, this is correct. The purpose of this lesson is to see how the 6.6.6.6/32 prefix is propagated throughout AS 12345. This is why you only see a single network command in the BGP configuration of R6 which is network 6.6.6.6 mask 255.255.255.255. This command advertises this network using BGP.
If you look at all of the other BGP routers in AS 12345, you will see that none of them has a network command in their BGP configurations. This means they are not advertising anything using BGP. So R6 receives no BGP updates and thus has no BGP routes beyond the one it generates itself.
If this were a production network, then you would have to advertise networks via BGP in AS 12345 as well in order to achieve proper routing.
I hope this has been helpful!
Laz
Hello Laz
Thank you. I understand well.
Regards,
Yoichi
According to the uploaded code, the topology ibgp does not have full mesh connection, since r1 needs load balancing and r1,r3 are not neighbors there is no case to perform load balancing…
Hello Konstantinos
The issue of load balancing here doesn’t relate directly to which iBGP routers R1 may be peers with. Regardless of whether or not R1 and R3 are peers, the topology as it stands can deliver more efficient routing if both paths via R2 and R3 are used by R1 to get to the 6.6.6.6/32 network. The fact that we are using an RR is irrelevant to load balancing.
Once R2 which is the RR is configured to advertise additional paths, then R1 learns about the alternative path via R3 → R5 and it can be configured to use it as a backup/repair path.
I hope this has been helpful!
Laz
go to R2(RR) :
router bgp 12345
address-family ipv4
neighbor 4.4.4.4 additional-paths send
bgp additional-paths select all
neighbor 4.4.4.4 advertise additional-paths all
Go to R4:
router bgp 12345
neighbor 2.2.2.2 additional-paths receive
address-family ipv4
bgp additional-paths select all
bgp additional-paths install
Probelm is R4 does not receive extra paths from R5, send the extra path and done!
Hello Konstantinos
Actually, this will not work because the additional-paths keyword can only be used for iBGP, as stated in the lesson. Even if you apply this configuration that you state, R4 will not consider the iBGP option over the eBGP option. As stated in my previous post, the only way to do this is to adjust the AD.
I hope this has been helpful!
Laz
Regarding this part of the lesson:
R3#show ip route 4.4.4.4 | include via
Known via “ospf 1”, distance 110, metric 3, type intra area 192.168.35.5, from 4.4.4.4,
01:13:48 ago, via GigabitEthernet0/3 *
192.168.23.2, from 4.4.4.4, 01:16:15 ago, via GigabitEthernet0/2
You said
“R3 uses two different paths to get to 4.4.4.4/32, we can go through R2 or R5. The path through R2 is not the most optimal path since it’s one more hop compared to the path through R5.”
According to the topology, 4.4.4.4 is two hops away regardless of whether you go through R5 or R2. (R2->R2->R4 vs R3->R5->R4).
Please help me to understand what was meant.
Hello Scott
You’re right. The number of hops is the same from R3 to R4 whether you go via R2 or R5. I will let Rene know to take a look at this section of the lesson so it can be revised accordingly.
Thanks for pointing that out!
Laz