Lab 8. OSPF - Virtual Link

Dalam OSPF sebuah area harus terhubung ke area 0 agar bisa berkomunikasi dengan area lain, pada kasus kali ini area 3 tidak terhubung langsung ke area 0 melainkan terhubung ke area 2 nah agar area 3 bisa tetap terhubung kita harus menggunakan yang namanya virtual link.

Konfigurasi R1

R1(config)#int f0/0
R1(config-if)#no sh
R1(config-if)#ip add 12.12.12.1 255.255.255.0
R1(config-if)#int lo0
R1(config-if)#ip add 1.1.1.1 255.255.255.255
#ospf
R1(config-if)#router ospf 1
R1(config-router)#net 1.1.1.1 0.0.0.0 area 0
R1(config-router)#net 12.12.12.0 0.0.0.255 area 1
R1(config-router)#router-id 1.1.1.1

Konfigurasi R2

R2(config)#int f0/0
R2(config-if)#no sh
R2(config-if)#ip add 12.12.12.2 255.255.255.0
R2(config-router)#int f0/1
R2(config-if)#no sh
R2(config-if)#ip add 23.23.23.2 255.255.255.0
R2(config-if)#int lo0
R2(config-if)#ip add 2.2.2.2 255.255.255.255
#ospf
R2(config-if)#router ospf 2
R2(config-router)#net 2.2.2.2 0.0.0.0 area 1
R2(config-router)#net 12.12.12.0 0.0.0.255 area 1
R2(config-router)#net 23.23.23.0 0.0.0.255 area 2
R2(config-router)#router-id 2.2.2.2

Konfiugrasi R3

R3(config)#int f0/0
R3(config-if)#no sh
R3(config-if)#ip add 23.23.23.3 255.255.255.0
R3(config-if)#int lo0
R3(config-if)#ip add 3.3.3.3 255.255.255.255
#ospf
R3(config-if)#router ospf 3
R3(config-router)#net 3.3.3.3 0.0.0.0 area 3
R3(config-router)#net 23.23.23.0 0.0.0.255 area 2
R3(config-router)#router-id 3.3.3.3

Cek table routing

R1(config-router)#do sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static 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 [110/2] via 12.12.12.2, 00:08:35, FastEthernet0/0
12.0.0.0/24 is subnetted, 1 subnets
C 12.12.12.0 is directly connected, FastEthernet0/0

bisa kita lihat diatas table routing tidak lengkap yakni loopback pada R3 yaitu 3.3.3.3 tidak terdeteksi, hal ini disebabkan karena R3 tidak terhubung ke area 0 secara langsung.lalu bagaimana agar R3 bisa terhubung ke area 0, kali ini kita akan mengkonfigurasikan yang namanya virtual link. fitur ini harus dikonfigurasikan di dua sisi yakni dari R2-R1 dan R3-R2, dimana R2 akan menjadi area transit bagi R3 untuk terhubung ke area 0 di R1.

#virtual link R1 area 1
R1(config-router)#router ospf 1
R1(config-router)#area 1 virtual-link 2.2.2.2
#virtual link R2 area 1 dan area 2
R2(config)#router ospf 2
R2(config-router)#area 1 virtu
R2(config-router)#area 1 virtual-link 1.1.1.1
R2(config-router)#area 2 virtual-link 3.3.3.3
#virtual link R3 ke area2
R3(config)#router ospf 3
R3(config-router)#area 2 virtual-link 2.2.2.2

sekarang kita cek kambali routing table nya

R1(config-router)#do sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static 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 [110/2] via 12.12.12.2, 00:04:13, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/3] via 12.12.12.2, 00:01:58, FastEthernet0/0
23.0.0.0/24 is subnetted, 1 subnets
O IA 23.23.23.0 [110/2] via 12.12.12.2, 00:01:58, FastEthernet0/0
12.0.0.0/24 is subnetted, 1 subnets
C 12.12.12.0 is directly connected, FastEthernet0/0

sekarang loopback R3 sudah terdeteksi di R1 dan jika di ping hasilnya akan

R1(config)#do ping 3.3.3.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/32/40 ms

dan jika di cek status virtual link sudah aktif

R3(config-router)#do sh ip ospf virtual-links
Virtual Link OSPF_VL0 to router 2.2.2.2 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 2, via interface FastEthernet0/0, Cost of using 1
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:00
Adjacency State FULL (Hello suppressed)
Index 1/2, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec

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