D-Link DES-3326 Adjacencies on Point-to-Point Interfaces, Ospf Packet Formats, Ospf Packet Header

DES-3326 Layer 3 Fast Ethernet Switch User’s Guide

Adjacencies on Point-to-Point Interfaces

OSPF Routers that are linked using point-to-point interfaces (such as serial links) will always form adjacencies. The concepts of DR and BDR are unnecessary.

OSPF Packet Formats

All OSPF packet types begin with a standard 24-byte header and there are five packet types. The header is described first, and each packet type is described in a subsequent section.

All OSPF packets (except for Hello packets) forward link-state advertisements. Link-State Update packets, for example, flood advertisements throughout the OSPF routing domain.

•OSPF packet header

•Hello packet

•Database Description packet

•Link-State Request packet

•The Link-State Update packet

•Link-State Acknowledgment packet

The OSPF Packet Header

Every OSPF packet is preceded by a common 24-byte header. This header contains the information necessary for a receiving router to determine if the packet should be accepted for further processing.

The format of the OSPP packet header is shown below:

OSPF Packet Header

Version No.

Type

Packet Length

Router ID

Area ID

Checksum Authentication Type

Authentication

Authentication

Figure 5-25. OSPF Packet Header

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