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Bgp route reflector

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

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Bgp route reflector

  1. 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. 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. 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. 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. 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. 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

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