Lab 69 - OSPF Filtering (Perbolehkan IP Genap)

Pada lab ini kita akan belajar melakukan filtering pada OSPF menggunakan distribute list. Berikut topologi yang akan kita gunakan pada lab ini

Gambar 1 Topologi jaringan OSPF

Diasumsikan kita telah mengkonfigurasi OSPF seperti topologi diatas, sehingga R2 dan R3 sudah memiliki tabel routing yang lengkap

R2(config-router)#do sh ip ro      
      11.0.0.0/32 is subnetted, 6 subnets
O        11.11.11.1 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
O        11.11.11.2 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
O        11.11.11.3 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
O        11.11.11.4 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
O        11.11.11.5 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
O        11.11.11.6 [110/11] via 12.12.12.1, 00:00:55, Ethernet0/0
      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

R3(config-router)#do sh ip ro

      11.0.0.0/32 is subnetted, 6 subnets
O        11.11.11.1 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
O        11.11.11.2 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
O        11.11.11.3 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
O        11.11.11.4 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
O        11.11.11.5 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
O        11.11.11.6 [110/21] via 23.23.23.2, 00:00:05, Ethernet0/0
      12.0.0.0/24 is subnetted, 1 subnets
O        12.12.12.0 [110/20] via 23.23.23.2, 00:00:05, Ethernet0/0
      23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        23.23.23.0/24 is directly connected, Ethernet0/0

Sekarang kita konfigurasi filtering agar R2 dan R3 hanya memiliki informasi tentang IP genap saja

R2(config)#access-list 1 permit 0.0.0.0 255.255.255.254
R2(config)#router ospf 1
R2(config-router)#distribute-list 1 in

Untuk pengujian kita coba lihat tabel routing pada R2 dan R3

R2(config-router)#do sh ip ro

      11.0.0.0/32 is subnetted, 3 subnets
O        11.11.11.2 [110/11] via 12.12.12.1, 00:00:43, Ethernet0/0
O        11.11.11.4 [110/11] via 12.12.12.1, 00:00:43, Ethernet0/0
O        11.11.11.6 [110/11] via 12.12.12.1, 00:00:43, Ethernet0/0
      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

R3(config-router)#do sh ip ro

      11.0.0.0/32 is subnetted, 6 subnets
O        11.11.11.1 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
O        11.11.11.2 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
O        11.11.11.3 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
O        11.11.11.4 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
O        11.11.11.5 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
O        11.11.11.6 [110/21] via 23.23.23.2, 00:06:43, Ethernet0/0
      12.0.0.0/24 is subnetted, 1 subnets
O        12.12.12.0 [110/20] via 23.23.23.2, 00:06:43, Ethernet0/0
      23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        23.23.23.0/24 is directly connected, Ethernet0/0

Perhatikan bahwa R3 tetap memiliki tabel routing yang lengkap. Filtering yang kita konfigurasikan di R2 tidak berpengaruh pada R3. Agar R3 hanya memiliki informasi tentang IP Genap saja, kita juga harus mengkonfigurasi filtering di R3

R3(config)#access-list 1 permit 0.0.0.0 255.255.255.254
R3(config)#router ospf 1
R3(config-router)#distribute-list 1 in

Sekarang kita coba lihat tabel routing di R3

R3(config-router)#do sh ip ro

      11.0.0.0/32 is subnetted, 3 subnets
O        11.11.11.2 [110/21] via 23.23.23.2, 00:00:22, Ethernet0/0
O        11.11.11.4 [110/21] via 23.23.23.2, 00:00:22, Ethernet0/0
O        11.11.11.6 [110/21] via 23.23.23.2, 00:00:22, Ethernet0/0
      12.0.0.0/24 is subnetted, 1 subnets
O        12.12.12.0 [110/20] via 23.23.23.2, 00:00:22, Ethernet0/0
      23.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        23.23.23.0/24 is directly connected, Ethernet0/0

Perhatikan bahwa saat ini R3 hanya memiliki informasi tentang IP Genap saja, sesuai dengan yang kita inginkan