Lab 16. OSPF Mindah Jalur

R1:
R1(config)#int fastEthernet 0/0
R1(config-if)#ip add 12.12.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#int gigabitEthernet 2/0
R1(config-if)#ip add 13.13.13.1 255.255.255.0
R1(config-if)#no shutdown
R1(config)#int lo0
R1(config-if)#ip add 1.1.1.1 255.255.255.255
R1(config-if)#exit
R1(config)#router ospf 1
R1(config-router)#network 0.0.0.0 255.255.255.255 area 0
R1(config-router)#auto-cost reference-bandwidth 1000
% OSPF: Reference bandwidth is changed.

Please ensure reference bandwidth is consistent across all routers

R2:

R2(config)#int fastEthernet 0/0

R2(config-if)#ip add 12.12.12.2 255.255.255.0

R2(config-if)#no shutdown

R2(config-if)#exit

R2(config)#int gigabitEthernet 3/0

R2(config-if)#ip add 23.23.23.2 255.255.255.0

R2(config-if)#no shutdown

R2(config-if)#exit

R2(config)#int lo0

R2(config-if)#ip add 2.2.2.2 255.255.255.255

R2(config-if)#exit

R2(config)#router ospf 2

R2(config-router)#network 0.0.0.0 255.255.255.255 area 0

R2(config-router)#auto-cost reference-bandwidth 1000

% OSPF: Reference bandwidth is changed.

Please ensure reference bandwidth is consistent across all routers

R3:

R3(config)#int gIgabitEthernet 2/0

R3(config-if)#ip add 23.23.23.3 255.255.255.0

R3(config-if)#no shutdown

R3(config-if)#exit

R3(config)#int Gigabitethernet 3/0

R3(config-if)#ip add 13.13.13.3 255.255.255.0

R3(config-if)#no shutdown

R3(config-if)#exit

R3(config)#int loopback 0

R3(config-if)#ip add 3.3.3.3 255.255.255.255

R3(config-if)#exit

R3(config)#router ospf 3

R3(config-router)#network 0.0.0.0 255.255.255.255 area 0

R3(config-router)#auto-cost reference-bandwidth 1000

R1:

R1(config)#do traceroute 2.2.2.2

Type escape sequence to abort.

Tracing the route to 2.2.2.2

VRF info: (vrf in name/id, vrf out name/id)

1 13.13.13.3 8 msec 88 msec 18 msec

2 23.23.23.2 40 msec 32 msec 33 msec

R1#show ip route 2.2.2.2

Routing entry for 2.2.2.2/32

   Known via "ospf 1", distance 110, metric 3, type intra area

   Last update from 13.13.13.3 on GigabitEthernet2/0, 00:41:25 ago

   Routing Descriptor Blocks:

   * 13.13.13.3, from 2.2.2.2, 00:41:25 ago, via GigabitEthernet2/0

        Route metric is 3, traffic share count is 1

Nah menurut informasi di atas nih temen-temen, jalur yang mengarah ke R2 itu melalui R3 terlebih dahulu, kenapaaaa ?? karena OSPF menggunakan bandwidth,. Dimana link gigabitethernet tentu nya lebih di pilih di banding dengan melalui interface fastethernet, selanjutnya perhatikan pada bagian metric nya yang bernilai 3, nilai 3 di dapatkan dari penjumlahan berikut.

(metric Link gigabitethernet R1-R3) + (metric link gigabitethernet R3-R2) + (metric loopback R3, 1+1+1=3

Nilai 1 berasal dari pembagian 1000.000.000 : 1000.000.000 (reference bandwidth nya sudah di rubah menjadi 1000Mbps), berikutnya kita shutdown terleih dahulu interface Gigabitethernet nya sehingga link akan menggunakan interface fastethernet nya.

R1:

R1(config)#int g2/0

R1(config-if)#shutdown

R1(config-if)#exit

R1(config)#do traceroute 2.2.2.2

Type escape sequence to abort.

Tracing the route to 2.2.2.2

VRF info: (vrf in name/id, vrf out name/id)

1 12.12.12.2 56 msec 64 msec 20 msec

R1#show ip route 2.2.2.2

Routing entry for 2.2.2.2/32

Known via "ospf 1", distance 110, metric 11, type intra area

Last update from 12.12.12.2 on FastEthernet0/0, 00:02:57 ago

Routing Descriptor Blocks:

* 12.12.12.2, from 2.2.2.2, 00:02:57 ago, via FastEthernet0/0

Route metric is 11, traffic share count is 1

Perhatikan pada metric nya yakni 11 merupakan penambahan link fastethernet R1-R2+link Lopback R3 (10+1). Nilai 10 didapat dari hasil pembagian 100.000.000:100.000.000 = 10

Nah sekarang coba kita no shutdown lagi interface gigabitethernet nya.

R1:

R1(config)#int g2/0

R1(config-if)#no shutdown

R1(config-if)#exit

Dan pastikan jalur yang di lewati R1 untuk menuju R2 melewati R3 kembali.

R1:

R1(config)#do sh ip route 2.2.2.2

Routing entry for 2.2.2.2/32 Known via "ospf 1", distance 110, metric 3, type intra area

Last update from 13.13.13.3 on GigabitEthernet2/0, 00:00:08 ago

Routing Descriptor Blocks:

* 13.13.13.3, from 2.2.2.2, 00:00:08 ago, via GigabitEthernet2/0

Route metric is 3, traffic share count is 1

Selanjutnya kita akan rubah bandwith Gigabitethernet menjadi 1000 agar ospf akan lewat langsung ke R2, walaupun arah R2 itu link nya adalah fastethernet, karena Fastethernet bandwith nya adallah 100.000 sedangkan gigabitethernet kita rubah menjadi 1000.

R1:

R1(config-if)#int g2/0

R1(config-if)#bandwidth 1000

Maka jalur akan berpindah langsung lewat R2 tidak melewati R3.

R1(config)#do sh ip route 2.2.2.2

Routing entry for 2.2.2.2/32 Known via "ospf 1", distance 110, metric 11, type intra area

Last update from 12.12.12.2 on FastEthernet0/0, 00:01:25 ago

Routing Descriptor Blocks:

* 12.12.12.2, from 2.2.2.2, 00:01:25 ago, via FastEthernet0/0

Route metric is 11, traffic share count is 1