OSPF Routing
Routing Open Shortest Path First (OSPF) adalah sebuah routing protocol standard terbuka yang telah diimplementasikan oleh sejumlah besar vendor jaringan. Alasan untuk mengkonfigurasi OSPF dalam sebuah topologi adalah untuk mengurangi overhead (waktu pemrosesan) routing, mempercepat convergance,serta membatasi ketidakstabilan network disebuah area dalam suatu network.

OSPF Message Encapsulation terjadi pada lapisan data-link dengan nomor protocol 89. Data field ini dapat berisi salah satu dari lima tipe paket OSPF. Pada IP packet header, alamat tujuannya mempunyai dua alamat multicast yaitu 224.0.0.5 dan 224.0.0.6 namun yang diset cukup salah satu dari alamat tersebut. Bila paket OSPF diencapsulasi di sebuah frame Ethernet, alamat tujuan dari MAC address juga merupakan sebuah alamat multicast, yaitu 01-00-5E-00-00-05 dan 01-00-5E-00-00-06. Semua paket OSPF mempunyai 24 byte yang berisikan informasi yang diperlukan. Packet header ini terdiri dari berbagai bidang seperti jenis-jenis paket OSPF, router ID serta alamat IP dari router yang mengirimkan paket.


Ada 5 tipe paket yang digunakan OSPF, yaitu :

*. Hello packet -> untuk menemukan serta membangun hubungan antar tetangga router OSPF.
*. Database Description (DBD)-> untuk mengecek singkronisasi database antar router.
*. Link-State Request (LSR) -> meminta spesifikasi link-state records antara router satu dengan yang lain.
*. Link-State Update (LSU) -> mengirimkan permintaan spesifikasi link-state records.
*. Link-State Acknowledgement (LSAck) -> menerima paket link-state.

OSPF adalah salah satu dari Interior Gateway Protocol (IGP) yang biasanya digunakan untuk routing protocol dalam satu routing domain yang sama.

Terdapat 2 macam routing protocol, yaitu Distance Vector dan Link State. Distance vector menggunakan kalkulasi distance atau jarak serta outgoing interface untuk memilih jalur yang paling baik ke network tujuan. Contoh dari Distance Vector adalah RIP, IGRP, dan EIGRP.
Link State memantau status dan tipe koneksi setiap link, kemudian membuat kalkulasi metric berdasarkan informasi tersebut. Contoh dari Link State adalah OSPF.

Router R1

R1(config)#router rip

R1(config-router)#network 192.168.0.0

R1(config-router)#network 150.72.21.0

R1(config-router)#end

Router R2

R2(config)#router rip

R2(config-router)#network 10.0.0.0

R2(config-router)#network 150.72.21.0

R2(config-router)#end

R1(config)#router rip

R1(config-router)#network 192.168.0.0

R1(config-router)#network 150.72.21.0

R1(config-router)#end

Router R2

R2(config)#router rip

R2(config-router)#network 10.0.0.0

R2(config-router)#network 150.72.21.0

R2(config-router)#end

R1(config)#router rip

R1(config-router)#network 192.168.0.0

R1(config-router)#network 150.72.21.0

R1(config-router)#end

Router R2

R2(config)#router rip

R2(config-router)#network 10.0.0.0

R2(config-router)#network 150.72.21.0

R2(config-router)#end

 

Router(config)# router ospf process_ID

Router(config-router)# network IP_address wildcard_mask area area_#

(1841Router0) Hostname R1

Router>enable

Router#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#hostname R1

R1(config)#interface fastethernet 0/0

R1(config-if)#ip address 10.0.0.1 255.0.0.0

R1(config-if)#no shutdown

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

R1(config-if)#exit
R1(config)#interface serial 0/0/0
R1(config-if)#ip address 20.0.0.1 255.0.0.0
R1(config-if)#clock rate 64000
R1(config-if)#bandwidth 64
R1(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/0/0, changed state to down
R1(config-if)#exit
%LINK-5-CHANGED: Interface Serial0/0/0, changed state to up
R1(config)#router ospf 1
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#network 20.0.0.0 0.255.255.255 area 0
R1(config-router)#exit
R1(config)#

(2620XM-Router1) Hostname R2


Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R2
R2(config)#interface serial 0/0
R2(config-if)#ip address 20.0.0.2 255.0.0.0
R2(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up
R2(config-if)#exit
R2(config)#interface fastethernet 0/0
R2(config-if)#ip address 30.0.0.1 255.0.0.0
R2(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
R2(config-if)#exit
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R2(config)#router ospf 2
R2(config-router)#network 20.0.0.0 0.255.255.255 area 0
R2(config-router)#network 3
00:03:10: %OSPF-5-ADJCHG: Process 2, Nbr 20.0.0.1 on Serial0/0 from
 LOADING to FULL, Loading Done0.0.0.0 0.255.255.255 area 0
R2(config-router)#network 30.0.0.0 0.255.255.255 area 0
R2(config-router)#exit
R2(config)#

2620XM-Router2)Hostname R3
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R3
R3(config)#interface fastethernet 0/0
R3(config-if)#ip address 30.0.0.2 255.0.0.0
R3(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R3(config-if)#interface serial 0/0
R3(config-if)#ip address 40.0.0.1 255.0.0.0
R3(config-if)#clock rate 64000
R3(config-if)#bandwidth 64
R3(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/0, changed state to down
R3(config-if)#exit
%LINK-5-CHANGED: Interface Serial0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up
R3(config)#router ospf 3
R3(config-router)#network 40.0.0.0 0.255.255.255 area 0
R3(config-router)#network 30.0.0.0 0.255.255.255 area 0
00:04:53: %OSPF-5-ADJCHG: Process 3, Nbr 30.0.0.1 on FastEthernet0/0 from
 LOADING to FULL, Loading D
R3(config-router)#exit
R3(config)#
%SYS-5-CONFIG_I: Configured from console by console
R3#

(2811Router3) Hostname R4
Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface serial 0/0/0
Router(config-if)#ip address 40.0.0.2 255.0.0.0
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface Serial0/0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to up
Router(config-if)#exit
Router(config)#interface fastethernet 0/0
Router(config-if)#ip address 50.0.0.1 255.0.0.0
Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
Router(config-if)#exit
R4(config)#router ospf 4
R4(config-router)#network 50.0.0.0 0.255.255.255 area 0
R4(config-router)#network 40.0.0.0 0.255.255.255 area 0
R4(config-router)#
00:06:32: %OSPF-5-ADJCHG: Process 4, Nbr 40.0.0.1 on Serial0/0/0 from
LOADING to FULL, Loading Done
R4(config-router)#exit
R4(config)#

(2811Router3) Hostname R4

Router>enable

Router#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#interface serial 0/0/0

Router(config-if)#ip address 40.0.0.2 255.0.0.0

Router(config-if)#no shutdown

%LINK-5-CHANGED: Interface Serial0/0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to up

Router(config-if)#exit

Router(config)#interface fastethernet 0/0

Router(config-if)#ip address 50.0.0.1 255.0.0.0

Router(config-if)#no shutdown

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

Router(config-if)#exit

R4(config)#router ospf 4

R4(config-router)#network 50.0.0.0 0.255.255.255 area 0

R4(config-router)#network 40.0.0.0 0.255.255.255 area 0

R4(config-router)#

00:06:32: %OSPF-5-ADJCHG: Process 4, Nbr 40.0.0.1 on Serial0/0/0 from

LOADING to FULL, Loading Done

R4(config-router)#exit

R4(config)#

PC-1

PC>ipconfig

IP Address......................: 10.0.0.2

Subnet Mask.....................: 255.0.0.0

Default Gateway.................: 10.0.0.1

PC>ping 50.0.0.2

PC-2

PC>ipconfig

IP Address......................: 50.0.0.2

Subnet Mask.....................: 255.0.0.0

Default Gateway.................: 50.0.0.1

PC>ping 10.0.0.2

R4#show ip protocols

Routing Protocol is "ospf 4"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  Router ID 50.0.0.1

  Number of areas in this router is 1. 1 normal 0 stub 0 nssa

  Maximum path: 4

  Routing for Networks:

    50.0.0.0 0.255.255.255 area 0

    40.0.0.0 0.255.255.255 area 0

  Routing Information Sources:

    Gateway         Distance      Last Update

    40.0.0.1             110      00:01:26

  Distance: (default is 110)

R4#show ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

       i - IS-IS, 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

O    10.0.0.0/8 [110/1564] via 40.0.0.1, 00:02:37, Serial0/0/0

O    20.0.0.0/8 [110/1563] via 40.0.0.1, 00:02:37, Serial0/0/0

O    30.0.0.0/8 [110/782] via 40.0.0.1, 00:02:37, Serial0/0/0

C    40.0.0.0/8 is directly connected, Serial0/0/0

C    50.0.0.0/8 is directly connected, FastEthernet0/0

R4#

Configuration command of OSPF

Commands	Descriptions
Router(config)#router ospf 1	Starts OSPF process 1. The process ID is any positive integer value between 1 and 65,535.
Router(config-router)#network 172.16.0.0 0.0.255.255 area 0	OSPF advertises interfaces, not networks. Uses the wildcard mask to determine which interfaces to advertise.
Router(config-if)#ip ospf hellointerval timer 20	Changes the Hello Interval timer to 20 seconds.
Router(config-if)#ip ospf deadinterval 80	Changes the Dead Interval timer to 80 seconds.
NOTE: Hello and Dead Interval timers must match for routers to become neighbors
Router#show ip protocol	Displays parameters for all protocols running on the router
Router#show ip route	Displays a complete IP routing table
Router#show ip ospf	Displays basic information about OSPF routing processes
Router#show ip ospf interface	Displays OSPF info as it relates to all interfaces
Router#show ip ospf interface fastethernet 0/0	Displays OSPF information for interface fastethernet 0/0
Router#show ip ospf border-routers	Displays border and boundary router information
Router#show ip ospf neighbor	Lists all OSPF neighbors and their states
Router#show ip ospf neighbor detail	Displays a detailed list of neighbors
Router#clear ip route *	Clears entire routing table, forcing it to rebuild
Router#clear ip route a.b.c.d	Clears specific route to network a.b.c.d
Router#clear ip opsf counters	Resets OSPF counters
Router#clear ip ospf process	Resets entire OSPF process, forcing OSPF to re-create neighbors, database, and routing table
Router#debug ip ospf events	Displays all OSPF events
Router#debug ip ospf adjacency	Displays various OSPF states and DR/ BDR election between adjacent routers
Router#debug ip ospf packets	Displays OPSF packets