Cisco: OSPF Howto

Sumber: https://www.techrepublic.com/article/how-to-configure-basic-ospf/

Open shortest path first, or OSPF, is a routing protocol that's based on open standards, meaning any vendor can implement its features. For years Cisco, Juniper, and other major networking vendors have coupled OSPF into their platform. When you configure OSPF, there are a few fundamental requirements in order to exchange routing information. To begin with, OSPF uses a Hello mechanism to detect neighboring devices that run OSPF. Once detected OSPF attempts to form an adjacency. Once an adjacency is established Link-State Advertisements (LSA) are used to exchange routing information.

The Hello packet is one of the first things you should have a solid understanding of. The following image shows the format of a Hello packet: 1.jpg Image: Brandon Carroll/TechRepublic

This packet is used by the Hello protocol, which is responsible for establishing and maintaining neighbor relationships. The Hello protocol also ensures that communication between neighbors is bidirectional. These packets get sent out of an interface where OSPF is enabled on a periodic basis. If a router receives a packet and sees its own address listed it knows that bidirectional communication exists. Once bidirectional communication is established a Designated Router (DR) is selected if on a multiaccess network. We're not going to cover that process in this article, however we highlight it because it's an integral part of OSPF. After two devices neighbor up, they synchronize Link-State databases.

SEE: 20 quick tips to make Linux networking easier

To configure basic OSPF to form a neighbor adjacency on a Cisco router perform the following:

• Identify the network interfaces that should run OSPF.
• Identify the OSPF area
• Issue the required commands to enable OSPF

Let's assume the following topology in which we are using OSPF area 5 and ABR5 and R5 are pre-configured for us. We need to enable OSPF on R6. 2.jpg Image: Brandon Carroll/TechRepublic

Start OSPF dengan meng-identifikasi router ospd (contoh 1):

enable
configure terminal
router ospf 1

Jalankan network untuk Interface yang menjalankan OSPF, menggunakan format berikut

network X.X.X.X W.W.W.W area A

Dimana:

• X.X.X.X - network address
• W.W.W.W - wildcard mask
• A - area ID.

Contoh:

network 10.0.0.80 0.0.0.3 area 5
network 10.0.0.84 0.0.0.3 area 5

W.W.W.W dihitung dari

255.255.255.255 - 255.255.255.252 = 0.0.0.3

Cek menggunakan neighbour & routing dengan perintah

show ip ospf neighbor
show ip ospf database 
show ip route

Referensi

• https://www.techrepublic.com/article/how-to-configure-basic-ospf/

Pranala Menarik

• Cisco