39.BGP - Split horizon 법칙 해결

요건 3. BGP Split Horizon 법칙 해결 (라우터 3개 부터)

ibgp로 광고받은 네트워크는 ibgp로

광고하지 못한다.

<R1>

router bgp 100
 bgp router-id 1.1.1.1
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 1.1.12.2 remote-as 100

<R2>

router bgp 100
 bgp router-id 2.2.2.2
 bgp log-neighbor-changes
 network 1.1.2.0 mask 255.255.255.0
 neighbor 1.1.12.1 remote-as 100
 neighbor 1.1.23.2 remote-as 100

<R3>

router bgp 100
 bgp router-id 3.3.3.3
 bgp log-neighbor-changes
 network 1.1.3.0 mask 255.255.255.0
 neighbor 1.1.23.1 remote-as 100
 neighbor 1.1.34.2 remote-as 100

<R4>

router bgp 100
 bgp router-id 4.4.4.4
 bgp log-neighbor-changes
 network 1.1.4.0 mask 255.255.255.0
 neighbor 1.1.34.1 remote-as 100

모두 연결되지 못한다.

 

<해결 방법>

1.Full Mesh

<R1>
Router(config)#router bgp 100
Router(config-router)#neighbor 1.1.23.2 remote-as 100
Router(config-router)#neighbor 1.1.34.2 remote-as 100

<R2>
router bgp 100
neighbor 1.1.34.2 remote-as 100

<R3>
router bgp 100
neighbor 1.1.12.1 remote-as 100

<R4>
router bgp 100
neighbor 1.1.12.1 remote-as 100
neighbor 1.1.23.1 remote-as 100

각각의 ibgp의 negibor를 잡아주어서 서로의 네이버가 되도록 만들면 문제를 해결할 수 있다.

2.Route Reflector

split horizon을 무시한다.

<R2>
router bgp 100
neighbor 1.1.12.1 route-reflector-client
neighbor 1.1.23.2 route-reflector-client

<R3>
router bgp 100
neighbor 1.1.23.1 route-reflector-client
neighbor 1.1.34.2 route-reflector-client

reflector-client는 자신의 네이버에만 줄 수 있다.

 

3.Confederation

router bgp [sub as number]

bgp confederation identifier [ original as number]

bgp confederation identifier [neighbor as number]

neighbro [ip address] remote-as [ neighbor sub as number]

 

<R1>
router bgp 10
bgp confederation identifier 100
bgp confederation peers 20
neighbor 1.1.12.2 remote-as0
network 1.1.1.0 mask 255.255.255.0

<R2>
router bgp 20
bgp confederation identifier 100
bgp confederation peers 10  30
neighbor 1.1.12.1 remote-as 10
network 1.1.2.0 mask 255.255.255.0
neighbor 1.1.23.2 remote-as 30

<R3>
router bgp 30
bgp confederation identifier 100
bgp confederation peers 20 40
neighbor 1.1.23.1 remote-as 20
neighbor 1.1.34.2 remote-as 40
network 1.1.3.0 mask 255.255.255.0

<R4>
router bgp 40
bgp confederation identifier 100
bgp confederation peer 30
neighbor 1.1.34.1 remote-as 30
network 1.1.4.0 mask 255.255.255.0

종합

BGP AS 100  => full-mesh 구조
<R1>
router rip
 version 2
 network 1.0.0.0
 network 192.168.10.0
 no auto-summary
!
router bgp 100
 network 192.168.10.0
 neighbor 1.1.12.2 remote-as 100
 neighbor 1.1.23.3 remote-as 100

<R2>
router rip
 version 2
 network 1.0.0.0
 network 192.168.20.0
 no auto-summary
!
router bgp 100
 network 192.168.20.0
 neighbor 1.1.12.1 remote-as 100
 neighbor 1.1.23.3 remote-as 100

<R3>
router rip
 version 2
 network 1.0.0.0
 network 4.0.0.0
 network 192.168.30.0
 no auto-summary
!
router bgp 100
 bgp log-neighbor-changes
 network 192.168.30.0
 neighbor 1.1.12.1 remote-as 100
 neighbor 1.1.23.2 remote-as 100
 neighbor 4.4.12.4 remote-as 200

BGP AS 200 -> route-reflector구조 
<R4>
router eigrp 100
 network 2.2.23.0 0.0.0.255
 network 4.4.12.0 0.0.0.255
 network 192.168.40.0
!
router bgp 200
 bgp log-neighbor-changes
 network 192.168.40.0
 neighbor 2.2.23.5 remote-as 200
 neighbor 4.4.12.3 remote-as 100

<R5>
router eigrp 100
 network 2.2.12.0 0.0.0.255
 network 2.2.23.0 0.0.0.255
 network 192.168.50.0
!
router bgp 200
 bgp log-neighbor-changes
 network 192.168.50.0
 neighbor 2.2.12.6 remote-as 200
 neighbor 2.2.12.6 route-reflector-client
 neighbor 2.2.23.4 remote-as 200
 neighbor 2.2.23.4 route-reflector-client

<R6>
router eigrp 100
 network 2.2.12.0 0.0.0.255
 network 5.5.12.0 0.0.0.255
 network 192.168.60.0
!
router bgp 200
 bgp log-neighbor-changes
 network 192.168.60.0
 neighbor 2.2.12.5 remote-as 200
 neighbor 5.5.12.7 remote-as 300

BGP AS 300 => confederation 구조 
<R7>
router ospf 1
 network 3.3.12.0 0.0.0.255 area 0
 network 5.5.12.0 0.0.0.255 area 0
 network 192.168.70.0 0.0.0.255 area 0
!
router bgp 10
 bgp log-neighbor-changes
 bgp confederation identifier 300
 bgp confederation peers 20
 network 192.168.70.0
 neighbor 3.3.12.8 remote-as 20
 neighbor 5.5.12.6 remote-as 200

<R8>
router ospf 1
 network 3.3.12.0 0.0.0.255 area 0
 network 3.3.34.0 0.0.0.255 area 0
 network 192.168.80.0 0.0.0.255 area 0
!
router bgp 20
 bgp log-neighbor-changes
 bgp confederation identifier 300
 bgp confederation peers 10 30
 network 192.168.80.0
 neighbor 3.3.12.7 remote-as 10
 neighbor 3.3.34.9 remote-as 30

<R9>
router ospf 1
 network 3.3.34.0 0.0.0.255 area 0
 network 192.168.90.0 0.0.0.255 area 0
!
router bgp 30
 bgp log-neighbor-changes
 bgp confederation identifier 300
 bgp confederation peers 20
 network 192.168.90.0
 neighbor 3.3.34.8 remote-as 20