D-Link DES-3326 manual Hello Packet, Field Description

		DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
Field	Description
Version No.	The OSPF version number
Type	The OSPF packet type. The OSPF packet types
	are as follows:
	Type	Description
	1	Hello
	2	Database Description
	3	Link-State Request
	4	Link-State Update
	5	Link-State Acknowledgment
Packet Length	The length of the packet in bytes. This length
	includes the 24-byte header.
Router ID	The Router ID of the packet’s source.
Area ID	A 32-bit number identifying the area that this
	packet belongs to. All OSPF packets are
	associated with a single area. Packets traversing a
	virtual link are assigned the backbone Area ID of
	0.0.0.0
Checksum	A standard IP checksum that includes all of the
	packet’s contents except for the 64-bit
	authentication field.
Authentication Type	The type of authentication to be used for the
	packet.
Authentication	A 64-bit field used by the authentication scheme.

Table 5-13. OSPF Packet Header

The Hello Packet

Hello packets are OSPF packet type 1. They are sent periodically on all interfaces, including virtual links, in order to establish and maintain neighbor relationships. In addition, Hello Packets are multicast on those physical networks having a multicast or broadcast capability, enabling dynamic discovery of neighboring routers.

All routers connected to a common network must agree on certain parameters such as the Network Mask, the Hello Interval, and the Router Dead Interval. These parameters are included in hello packets, so that differences can inhibit the forming of neighbor relationships. A detailed explanation of the receive processing for Hello packets, so that differences can inhibit the forming of neighbor relationships.

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