Day 3 - OSPF Summarization - Area Range

Pada routing OSPF, summarization hanya dapat dilakukan oleh 2 jenis router, yaitu :
1. ABR (Internal Route) -> menggunakan command 'area xx range'
2. ASBR (External Route) -> menggunakan command 'summary-address'

Lab kali ini kita akan membahas bagaimana cara melakukan route summarization menggunakan command 'area xx range'.

Lab 14 - OSPF Summarization - Area Range

Topologi yang digunakan adalah sbb :


Konfigurasi R1 :

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
!
interface Loopback1
 ip address 100.100.100.1 255.255.255.255
!
interface Loopback2
 ip address 100.100.100.2 255.255.255.255
!
interface Loopback3
 ip address 100.100.100.3 255.255.255.255
!
interface Loopback4
 ip address 100.100.100.4 255.255.255.255
!
interface Serial0/0
 ip address 12.12.12.1 255.255.255.0
!

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

 network 100.100.100.1 0.0.0.0 area 1
 network 100.100.100.2 0.0.0.0 area 1
 network 100.100.100.3 0.0.0.0 area 1
 network 100.100.100.4 0.0.0.0 area 1

Konfigurasi R2 :

interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface FastEthernet0/0
 ip address 23.23.23.2 255.255.255.0
!
interface Serial0/0
 ip address 12.12.12.2 255.255.255.0
!

router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

Konfigurasi R3 :

interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface FastEthernet0/0
 ip address 23.23.23.3 255.255.255.0
!

router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 network 0.0.0.0 255.255.255.255 area 0

Kita cek routing table di R3 :

Gateway of last resort is not set
     1.0.0.0/32 is subnetted, 1 subnets
O       1.1.1.1 [110/75] via 23.23.23.2, 00:00:29, FastEthernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/11] via 23.23.23.2, 00:00:29, FastEthernet0/0
     100.0.0.0/32 is subnetted, 4 subnets
O IA    100.100.100.4 [110/75] via 23.23.23.2, 00:00:29, FastEthernet0/0
O IA    100.100.100.1 [110/75] via 23.23.23.2, 00:00:29, FastEthernet0/0
O IA    100.100.100.2 [110/75] via 23.23.23.2, 00:00:29, FastEthernet0/0
O IA    100.100.100.3 [110/75] via 23.23.23.2, 00:00:29, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
C       3.3.3.3 is directly connected, Loopback0
     23.0.0.0/24 is subnetted, 1 subnets
C       23.23.23.0 is directly connected, FastEthernet0/0
     12.0.0.0/24 is subnetted, 1 subnets
O       12.12.12.0 [110/74] via 23.23.23.2, 00:00:30, FastEthernet0/0

Terlihat bahwa untuk semua routing IP Loopback R1 sudah diterima oleh R3 via routing OSPF.

Sekarang kita coba lakukan summarization di router R1.
R1(config-router)#area 1 range 100.100.100.0 255.255.255.248


Kita coba cek lagi di routing table R3 :

R3#sh ip route
Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
O       1.1.1.1 [110/75] via 23.23.23.2, 00:01:33, FastEthernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/11] via 23.23.23.2, 00:01:33, FastEthernet0/0
     100.0.0.0/29 is subnetted, 1 subnets
O IA    100.100.100.0 [110/75] via 23.23.23.2, 00:00:20, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
C       3.3.3.3 is directly connected, Loopback0
     23.0.0.0/24 is subnetted, 1 subnets
C       23.23.23.0 is directly connected, FastEthernet0/0
     12.0.0.0/24 is subnetted, 1 subnets
O       12.12.12.0 [110/74] via 23.23.23.2, 00:01:33, FastEthernet0/0

Terlihat bahwa sekarang R3 hanya menerima 1 baris routing dari IP Loopback R1, yaitu 100.100.100.0/29 via routing OSPF.


Kita cek juga routing table di R1 :
R1(config-router)#do sh ip route
Gateway of last resort is not set

     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
O       2.2.2.2 [110/65] via 12.12.12.2, 00:01:36, Serial0/0
     100.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
C       100.100.100.4/32 is directly connected, Loopback4
O       100.100.100.0/29 is a summary, 00:01:36, Null0
C       100.100.100.1/32 is directly connected, Loopback1
C       100.100.100.2/32 is directly connected, Loopback2
C       100.100.100.3/32 is directly connected, Loopback3
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/75] via 12.12.12.2, 00:01:36, Serial0/0
     23.0.0.0/24 is subnetted, 1 subnets
O       23.23.23.0 [110/74] via 12.12.12.2, 00:01:37, Serial0/0
     12.0.0.0/24 is subnetted, 1 subnets
C       12.12.12.0 is directly connected, Serial0/0


Pada OSPF, discard route (Null0) akan otomatis muncul apabila kita melakukan route summarization.

Hal tersebut untuk menghindari terjadinya forwarding loop.

Bila ingin dihapuskan, bisa dengan menambahkan command sbb :
R1(config-router)#no discard-route internal

R1(config-router)#do sh ip route

Gateway of last resort is not set

     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
O       2.2.2.2 [110/65] via 12.12.12.2, 00:00:09, Serial0/0
     100.0.0.0/32 is subnetted, 4 subnets
C       100.100.100.4 is directly connected, Loopback4
C       100.100.100.1 is directly connected, Loopback1
C       100.100.100.2 is directly connected, Loopback2
C       100.100.100.3 is directly connected, Loopback3
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/75] via 12.12.12.2, 00:00:09, Serial0/0
     23.0.0.0/24 is subnetted, 1 subnets
O       23.23.23.0 [110/74] via 12.12.12.2, 00:00:09, Serial0/0
     12.0.0.0/24 is subnetted, 1 subnets
C       12.12.12.0 is directly connected, Serial0/0
 
Terlihat bahwa sekarang sudah tidak ada lagi discard route di routing table R1 :)