What is Route Reflector, Why BGP Route Reflector, How to configure BGP Route Reflector ? How to configure BGP ? Basic BGP.

1. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
Today we will cover about BGP Route Reflector.
BGP (Border Gateway Protocol) Route Reflector:
Here I am not covering the basic BGP but it is necessary that you should know about basic BGP as what is IBGP?
What is EBGP? Etc.
Before move to BGP route reflector, we will discuss some basic concept and requirement.
What is BGP Route Reflector?
Instead of establishing an IBGP (Internal BGP, Means in a same AS) peering with each and every router of the
IBGP mesh, routers establish IBGP sessions with route reflectors (RR) only. RRs represent a focal point for IBGP
sessions, and form a cluster together with its clients, that is, other routers within an internal BGP mesh.
A route reflector is BGP router that is allowed to break the iBGP loop avoidance rule. Route reflectors can
advertise updates received from an iBGP peer to another iBGP peer under specific conditions.
By breaking the rules, route reflectors are used to eliminate the full mesh requirement and allow for building
iBGP networks that scale easily and cleanly.
Like route reflectors, confederations are used to reduce the amount of IBGP meshing needed. Without route
reflectors or confederation, IBGP requires a full mesh of peering relationships
Why it need?
BGP split-horizon rule: that any route received from an iBGP neighbor must not be advertised to any other iBGP
neighbor. As below network diagram -

2. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
To resolve the above issue, we need full Mesh IBGP peering or router reflector. But full mesh peering is not
practically in production network because it will very difficult to maintain too much peering. So router reflector
is good solution.
Let’s check network without router reflector:
R1 Router configuration:
-----Output Cut-----
!
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
router bgp 6500
no synchronization
bgp router-id 1.1.1.1
bgp log-neighbor-changes
network 192.168.1.0
neighbor 192.168.1.2 remote-as 6500
no auto-summary
!
-----Output Cut--------
R2 Router configuration:
----Output Cut------
interface FastEthernet0/0
ip address 192.168.1.2 255.255.255.0
duplex auto
speed auto
!

3. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
interface FastEthernet0/1
ip address 192.168.2.1 255.255.255.0
duplex auto
speed auto
!
router bgp 6500
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 192.168.1.0
network 192.168.2.0
neighbor 192.168.1.1 remote-as 6500
neighbor 192.168.2.2 remote-as 6500
no auto-summary
!
----Output Cut------
R3 Router Running configuration:
-----Output Cut----
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 192.168.2.2 255.255.255.0
duplex auto
speed auto
!
router bgp 6500
no synchronization
bgp router-id 3.3.3.3
bgp log-neighbor-changes
network 1.1.1.0 mask 255.255.255.0
network 192.168.2.0

4. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
neighbor 192.168.2.1 remote-as 6500
no auto-summary
!
Let’s check all routers output:
Commands: Show IP BGP & Show IP BGP Summery
R1 Output:

5. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
R2 Output:
R3 Output:

6. BGP Route Reflector Document Version 1
Deepak Kumar (deepuverma@outlook.com), Call: - +91 - 8875332931 / 9214012330
Updated material may be found at http://www.deepuverma.in
LinkedIn: - https://in.linkedin.com/in/engdeepak Twitter: - https://twitter.com/Deepakkhw
I advertised a network 1.1.1.0/24 from router R3 and it will learn on R2 but it will not learn on R1.
Let’s configure Router Reflector on R2:
!
router bgp 6500
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 192.168.1.0
network 192.168.2.0
neighbor 192.168.1.1 remote-as 6500
neighbor 192.168.1.1 route-reflector-client
neighbor 192.168.2.2 remote-as 6500
neighbor 192.168.2.2 route-reflector-client
no auto-summary
!
After configuration router reflector on R2, We will check the BGP table on R1
Here you can see that we will learn 1.1.1.0/24 on R1 and it will install in routing table also.
Next document:: we will learn more about Route Reflector