OSPF Virtual Links
Halo semua kembali lagi di blog ini, Kali ini kita akan membahas materi OSPF Vritual Links, Apa itu OSPF Virtual Links, Apa fungsi nya, Dan bagaimana penerapan nya akan kita bahas pada tulisan kali ini. Untuk teori dasar OSPF kita sudah pernah membahas pada blog ini, Dan ini adalah salah satu materi lanjutan dari OSPF. Baik langsung saja kita mulai.
Virtual Links
Kita tahu bahwa agar area pada OSPF dapat saling berkomunikasi maka harus terhubung langsung pada area 0 atau disebut juga backbone area. Ketika pada kondisi dimana router dengan area yang berbeda tidak dapat terhubung langsung dengan area 0 kita bisa memanfaatkan Virtual Links agar area tersebut dapat berkomunikasi dengan area lain. Virtual Links akan menjembatani area yang tidak terhubung ke area 0 tersebut dengan area yang terdekat dan mengadvertise network tersebut.
Topologi
Berikut topologi yang akan kita gunakan pada Lab kali ini, Dimana area 2 dan area 3 tidak terhubung langsung dengan Area 0. Maka kita akan membuat Virtual Links untuk menjembatani area 2 dan juga area 3 tersebut.
Lab
Konfigurasi IP Address dan advertise kedalam routing OSPF.
R1 ===== R1(config)#interface lo0 R1(config-if)#ip add 1.1.1.1 255.255.255.255 R1(config-if)#int Gi0/0 R1(config-if)#ip add 12.12.12.1 255.255.255.0 R1(config-if)#ip ospf network point-to-point R1(config-if)#no shutdown R1(config)#router ospf 1 R1(config-router)#router-id 1.1.1.1 R1(config-router)#network 1.1.1.1 0.0.0.0 area 0 R1(config-router)#network 12.12.12.1 0.0.0.0 area 1 R1(config-router)#exit
R2 ===== R2(config)#int lo0 R2(config-if)#ip add 2.2.2.2 255.255.255.255 R2(config)#int Gi0/0 R2(config-if)#ip add 12.12.12.2 255.255.255.0 R1(config-if)#ip ospf network point-to-point R2(config-if)#no shutdown R2(config)#int Gi0/1 R2(config-if)#ip add 23.23.23.2 255.255.255.0 R1(config-if)#ip ospf network point-to-point R2(config-if)#no shutdown R2(config-if)#exit R2(config)#router ospf 2 R2(config-router)#router-id 2.2.2.2 R2(config-router)#net 2.2.2.2 0.0.0.0 area 1 R2(config-router)#net 12.12.12.2 0.0.0.0 area 1 R2(config-router)#net 23.23.23.2 0.0.0.0 area 2 R2(config-router)#exit
R3 ===== R3(config)#interface loopback 0 R3(config-if)#ip address 3.3.3.3 255.255.255.255 R3(config)#int g1/0 R3(config-if)#ip add 23.23.23.3 255.255.255.0 R1(config-if)#ip ospf network point-to-point R3(config-if)#no shutdown R3(config)#router ospf 3 R3(config-router)#router-id 3.3.3.3 R3(config-router)#net 3.3.3.3 0.0.0.0 area 3 R3(config-router)#net 23.23.23.3 0.0.0.0 areaKonfigurasi Virtual Links dengan format area area-id virtual-link router-id
R1 ===== R1(config)#router ospf 1 R1(config-router)#area 1 virtual-link 2.2.2.2 R1(config-router)#exit
R2 ===== R2(config)#router ospf 2 R2(config-router)#area 1 virtual-link 1.1.1.1 R2onfig-router)#exit ====== Notifikasi FULL State ====== R2# *Jul 24 00:55:13.199: %OSPF-5-ADJCHG: Process 2, Nbr 1.1.1.1 on OSPF_VL0 from LOADING to FULL, Loading DoneSampai sini kita sudah membuat Virtual Links untuk area 2, Namun area 3 masih belum ada jembatan untuk terhubung ke area 0, Maka kita akan tambahkan Virtual Links lagi dari area 2 untuk menjembatani network pada area 3.
R2 ===== R2(config)#router ospf 2 R2(config-router)#area 2 virtual-link 3.3.3.3 R2(config-router)#exit
R3 ===== R3(config)#router ospf 3 R3(config-router)#area 2 virtual-link 2.2.2.2 R3(config-router)#exit
Verifikasi
Routing tabel
=====
R1#show ip route
Codes: L - local, 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, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
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, 01:07:59, GigabitEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/3] via 12.12.12.2, 00:10:25, GigabitEthernet0/0
12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 12.12.12.0/24 is directly connected, GigabitEthernet0/0
L 12.12.12.1/32 is directly connected, GigabitEthernet0/0
23.0.0.0/24 is subnetted, 1 subnets
O IA 23.23.23.0 [110/2] via 12.12.12.2, 01:07:39, GigabitEthernet0/0
OSPF Virtual Links
=====
R2#show ip ospf virtual-links
Virtual Link OSPF_VL1 to router 3.3.3.3 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 2, via interface GigabitEthernet0/1
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Adjacency State FULL (Hello suppressed)
Index 1/2/4, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec
Virtual Link OSPF_VL0 to router 1.1.1.1 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 1, via interface GigabitEthernet0/0
Topology-MTID Cost Disabled Shutdown Topology Name
0 1 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:08
Adjacency State FULL (Hello suppressed)
Index 1/1/2, retransmission queue length 0, number of retransmission 1
First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0)
Last retransmission scan length is 1, maximum is 1
Last retransmission scan time is 1 msec, maximum is 1 msec
LSA Database
=====
R1#sh ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 232 0x80000006 0x009A46 2
2.2.2.2 2.2.2.2 1 (DNA) 0x80000006 0x00BECC 2
3.3.3.3 3.3.3.3 2 (DNA) 0x80000006 0x00CBF6 1
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
2.2.2.2 1.1.1.1 232 0x80000003 0x001F0E
2.2.2.2 2.2.2.2 1472 (DNA) 0x80000002 0x00F832
3.3.3.3 3.3.3.3 6 (DNA) 0x80000001 0x00AE75
12.12.12.0 1.1.1.1 232 0x80000003 0x00BF52
12.12.12.0 2.2.2.2 1472 (DNA) 0x80000002 0x00A36B
23.23.23.0 2.2.2.2 1472 (DNA) 0x80000002 0x0016D7
23.23.23.0 3.3.3.3 6 (DNA) 0x80000001 0x00F9F0
Router Link States (Area 1)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 232 0x80000007 0x00F7C6 2
2.2.2.2 2.2.2.2 202 0x80000006 0x002F72 3
Summary Net Link States (Area 1)
Link ID ADV Router Age Seq# Checksum
1.1.1.1 1.1.1.1 232 0x80000003 0x0043EE
3.3.3.3 2.2.2.2 793 0x80000001 0x00D650
23.23.23.0 2.2.2.2 202 0x80000003 0x0014D8
Connectivity ===== R1#ping 3.3.3.3 size 512 repeat 20 Type escape sequence to abort. Sending 20, 512-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds: !!!!!!!!!!!!!!!!!!!! Success rate is 100 percent (20/20), round-trip min/avg/max = 4/5/7 msBaik sampai sini kita telah membuat Virtual Links untuk area 2 dan area 3, Mungkin cukup sekian pembahasan materi dan lab OSPF Virtual Link kali ini semoga bermanfaat.
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