Lab 84 - BGP Attribute (Community No-Advertise)

Pada lab sebelumnya kita telah belajar tentang Community No-Export, selanjutnya pada lab ini kita akan belajar tentang Community No-Advertise. Berikut topologi yang akan kita gunakan pada lab ini

Gambar 1 Topologi jaringan BGP

Diasumsikan kita udah konfig BGP seperti lab sebelumnya ya.. Pastikan R1, R2, dan R4 masih punya informasi tentang 3.3.3.3

R1(config-router)#do sh ip ro
1.0.0.0/32 is subnetted, 1 subnets
C        1.1.1.1 is directly connected, Loopback0
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [200/0] via 12.12.12.2, 00:00:20
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [200/0] via 12.12.12.2, 00:00:51
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [200/0] via 12.12.12.2, 00:00:51
      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        12.12.12.0/24 is directly connected, Ethernet0/0

R2(config-router)#do sh ip ro

      1.0.0.0/32 is subnetted, 1 subnets
B        1.1.1.1 [200/0] via 12.12.12.1, 00:01:21
      2.0.0.0/32 is subnetted, 1 subnets
C        2.2.2.2 is directly connected, Loopback0
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [200/0] via 23.23.23.3, 00:01:21
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [20/0] via 24.24.24.4, 00:01:21
      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        12.12.12.0/24 is directly connected, Ethernet0/0
      23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        23.23.23.0/24 is directly connected, Ethernet0/1
      24.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        24.24.24.0/24 is directly connected, Ethernet0/2

R4(config-router)#do sh ip ro

      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 24.24.24.2, 00:01:17
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [20/0] via 24.24.24.2, 00:01:48
      4.0.0.0/32 is subnetted, 1 subnets
C        4.4.4.4 is directly connected, Loopback0
      24.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        24.24.24.0/24 is directly connected, Ethernet0/0

Sip2 semua masih punya informasi tentang 3.3.3.3, sekarang kita hanya akan konfig community no advertise di R3.

R3(config)#access-list 1 permit 3.3.3.3
R3(config)#route-map NO-ADVERTISE permit 10
R3(config-route-map)#match ip address 1
R3(config-route-map)#set community no-advertise 
R3(config-route-map)#route-map NO-ADVERTISE permit 20

R3(config-route-map)#router bgp 3
R3(config-router)#neighbor 23.23.23.2 route-map NO-ADVERTISE out
R3(config-router)#neighbor 23.23.23.2 send-community 

Kita perlu membuat dua route-map, yaitu dengan sequence 10 dan 20. route-map dengan sequence 10 kita gunakan untuk set community network 3.3.3.3, sedangkan sequence 20 digunakan untuk mengizinkan semua network kecuali 3.3.3.3

Oke untuk pengujian kita coba lihat status di R2, pastikan network 3.3.3 sudah punya community no-advertise

R2(config-router)#do sh ip bgp 3.3.3.3
BGP routing table entry for 3.3.3.3/32, version 6
Paths: (1 available, best #1, table default, not advertised to any peer)
  Not advertised to any peer
  (3)
    23.23.23.3 from 23.23.23.3 (3.3.3.3)
      Origin IGP, metric 0, localpref 100, valid, confed-external, best
      Community: no-advertise

Jozzzz kalo udah gini seharusnya R1 dan R4 udah gak punya informasi tentang 3.3.3.3

R1(config-router)#do sh ip ro

      1.0.0.0/32 is subnetted, 1 subnets
C        1.1.1.1 is directly connected, Loopback0
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [200/0] via 12.12.12.2, 00:04:14
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [200/0] via 12.12.12.2, 00:04:45
      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        12.12.12.0/24 is directly connected, Ethernet0/0

R4(config-router)#do sh ip ro

      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 24.24.24.2, 00:04:34
      4.0.0.0/32 is subnetted, 1 subnets
C        4.4.4.4 is directly connected, Loopback0
      24.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        24.24.24.0/24 is directly connected, Ethernet0/0

Tuh kan bener.... jadi kesimpullannya adalah jika suatu network punya community no advertise, maka network tersebut tidak akan diadvertise ke router lain, entah itu router yang berada dalam satu AS yang sama ataupun yang berada di AS lain