MPLS L3 VPN with Route Reflectors

Hi Fellas,


Lets put some spice on classic MPLS cliche design with Route Reflectors.
If we are lucky, 3 or 4 IBGP router peering is nothing when we try to configure I-BGP peering ;full mesh. But If we don't....







 In BGP, updates received by a peer in an AS are not allowed to be forwarded to another peer within the same AS. 
That's why we need to use full-mesh to make neighbor each IBGP Router.


We need to determine n*(n-1)/2 peerings in IBGP domain... This is sucks when we have more than at least 5 routers 5*4/2 = 10 peerings !!!!!

PS: IBGP Routers do not need to directly connected like EIGRP or OSPF. !

PS2 : When a prefix is learned by another IBGP router ; the advertised prefix's next-hop address remains the same. Against that problem we can use these:

- Next-hop-self command or
-Advertise prefixes

Otherwise;







When you configure a route reflector you have to tell the router whether the other IBGP router is a client or non-client. A client is an IBGP router that the route reflector will “reflect” routes to, the non-client is just a regular IBGP neighbor.

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.

1. A route learned from an EBGP neighbor can be forwarded to another EBGP neighbor, a client and non-client.
2. A route learned from a client can be forwarded to another EBGP neighbor, client and non-client.
3. A route learned from a non-client can be forwarded to another EBGP neighbor and client, but not to a non-client.

Shortly;

Client: Will be reflect routes comes from others. (like HQ or Hub or something :) )
Non-Client : Will act like a regular IGBP router.

• Any updates would be sent to the RR alone.
•  The RRs are then responsible for propagating information received from PEs to all other PEs.
•  Each time a PE is added, a neighbor statement pointing to the RR needs to be added on the new PE router, and on the RR, a neighbor statement pointing to the PE must be added.

Route-Reflector-Client with Layer 3 VPN :

Customer A (R5-R6) contains IGP AS 51 Area 1
Provider Site : BG1 , OSPF 100 Area0
VPN Connection PE ; Router Ospf 50 Area 1

R1(config)#int fa0/0

R1(config-if)#ip os 1 ar 0

R1(config-if)#mpls ip

R1(config-if)#int fa0/1

R1(config-if)#ip os 1 ar 0

R1(config-if)#mpls ip
R1(config-if)#int lo 0

R1(config-if)#ip os 1 ar 0

R1(config-if)#exit

R2(config)#int fa0/0

R2(config-if)#ip os 1 ar 0

R2(config-if)#mpls ip

R2(config-if)#int fa0/1

R2(config-if)#ip os 1 ar 0

R2(config-if)#mpls ip
R2(config-if)#int lo0

R2(config-if)#ip os 1 ar 0

R2(config-if)#exit

R3(config)#int fa0/0

R3(config-if)#ip os 1 ar 0

R3(config-if)#mpls ip

R3(config-if)#int fa0/1

R3(config-if)#ip os 1 ar 0

R3(config-if)#mpls ip

R3(config-if)#int lo0

R3(config-if)#ip os 1 ar 0

R3(config-if)#exit

R4(config)#int fa0/0

R4(config-if)#ip os 1 ar 0

R4(config-if)#mpls ip

R4(config-if)#int fa0/1

R4(config-if)#ip os 1 ar 0

R4(config-if)#mpls ip

R4(config-if)#int lo0

R4(config-if)#ip os 1 ar 0

R4(config-if)#exit

R3(config)#ip vrf Cust_A

R3(config-vrf)# description Customer-A

R3(config-vrf)# rd 1:100

R3(config-vrf)# route-target export 1:100

R3(config-vrf)# route-target import 1:100

R3(config-vrf)#exit

R3(config)#int fa1/0

R3(config-if)#ip vrf forwarding Cust_A

R4(config)#ip vrf Cust_A

R4(config-vrf)# description Customer-A

R4(config-vrf)# rd 1:100

R4(config-vrf)# route-target export 1:100

R4(config-vrf)# route-target import 1:100

R4(config-vrf)#exit

PE2(config)#int fa1/0

PE2(config-if)#ip vrf forwarding Cust_A

PE2(config-if)#exit

R3(config)#router ospf 50 vrf Cust_A

R3(config-router)# log-adjacency-changes

R3(config-router)# network 172.23.54.0 0.0.0.255 area1

R3(config-router)#exit

R4(config)#router ospf 100 vrf Cust_A

R4(config-router)# log-adjacency-changes

R4(config-router)# network 172.23.53.0 0.0.0.255 area 1

R4(config-router)#exit

R5(config)#int lo 0

R5(config-if)# ip ospf 51 area 1

R5(config-if)#int fa0/0

R5(config-if)# ip ospf 51 area 1

R5(config-if)#exit

R6(config)#int lo 0

R6(config-if)# ip ospf 51 area 1

R6(config-if)#int fa0/0

R6(config-if)# ip ospf 51 area 1

R6(config-if)#exit

R3(config)#router ospf 50 vrf Cust_A

R3(config-router)# redistribute bgp 1 subnets

R3(config-router)#exit

R3(config)#router bgp 1

R3(config-router)#address-family ipv4 vrf Cust_A

R3(config-router-af)#redistribute os 50 vrf Cust_A

R4(config)#router ospf 50 vrf Cust_A

R4(config-router)# redistribute bgp 1 subnets

R4(config-router)#exit

R4(config)#router bgp 1

R4(config-router)#address-family ipv4 vrf Cust_A

R4(config-router-af)#redistribute os 50 vrf Cust_A 

R3(config)#router bgp 1

R3(config-router)# neighbor 2.2.2.2 remote-as 1

R3(config-router)# neighbor 2.2.2.2 update-source Loopback0

R3(config-router)# neighbor 3.3.3.3 remote-as 1

R3(config-router)# neighbor 3.3.3.3 update-source Loopback0

R3config-router)# address-family vpnv4

R3(config-router-af)#  neighbor 2.2.2.2 activate

R3(config-router-af)#  neighbor 2.2.2.2 send-community both

R3(config-router-af)#  neighbor 3.3.3.3 activate

R3(config-router-af)#  neighbor 3.3.3.3 send-community both

R3(config-router-af)# exit-address-family

R3(config-router)#exit

R4(config)#router bgp 1

R4(config-router)# neighbor 2.2.2.2 remote-as 1

R4(config-router)# neighbor 2.2.2.2 update-source Loopback0

R4(config-router)# neighbor 3.3.3.3 remote-as 1

R4config-router)# neighbor 3.3.3.3 update-source Loopback0

R4(config-router)# address-family vpnv4

R4(config-router-af)#  neighbor 2.2.2.2 activate

R4(config-router-af)#  neighbor 2.2.2.2 send-community both

R4(config-router-af)#  neighbor 3.3.3.3 activate

R4(config-router-af)#  neighbor 3.3.3.3 send-community both

R4(config-router-af)# exit-address-family

R4(config-router)#exit

R3(config)#router bgp 1

R3(config-router)#neighbor RR1 peer-group

R3(config-router)#neighbor RR1 remote-as 1

R3(config-router)#address-family vpnv4

R3(config-router-af)#neighbor 4.4.4.4 peer-group RR1

R3(config-router-af)#neighbor 5.5.5.5 peer-group RR1

R3(config-router-af)#neighbor RR1 route-reflector-client

R3(config-router-af)#end

R4(config)#router bgp 1

R4(config-router)#neighbor RR2 peer-group

R4(config-router)#neighbor RR2 remote-as 1

R4(config-router)#address-family vpnv4

R4(config-router-af)#neighbor 4.4.4.4 peer-group RR2

R4(config-router-af)#neighbor 5.5.5.5 peer-group RR2

R4(config-router-af)#neighbor RR2 route-reflector-client

R4(config-router-af)#end