OSPF NETWORK TYPES

There are five different network types within which OSPF operates. The following list explains the characteristics of the OSPF network types:

Broadcast

The Broadcast network type is the default for an OSPF enabled Ethernet interface.
The Broadcast network type requires that a link support Layer 2 Broadcast capabilities.
The Broadcast network type has a 10 second hello and 40 second dead timer.
An OSPF Broadcast network type requires the use of a DR/BDR.

Non-Broadcast

The Non-Broadcast network type is the default for OSPF enabled frame relay physical interfaces.
Non-Broadcast networks requires the configuration of static neighbors; hello’s are sent via unicast.
The Non-Broadcast network type has a 30 second hello and 120 second dead timer.
An OSPF Non-Broadcast network type requires the use of a DR/BDR

Point-to-Point

A Point-to-Point OSPF network type does not maintain a DR/BDR relationship.
The Point-to-Point network type has a 10 second hello and 40 second dead timer.
Point-to-Point network types are intended to be used between 2 directly connected routers.

Point-to-Multipoint Non-Broadcast

Same as Point-to-Multipoint but requires static neighbors. Used on Non-broadcast layer 2 topologies.
Gives you the ability to define link cost on a per neighbor basis.

Point-to-Multipoint

OSPF treats Point-to-Multipoint networks as a collective of point-to-point links.
Point-to-Multipoint networks do not maintain a DR/BDR relationship.
Point-to-Multipoint networks advertise a hot route for all the frame-relay endpoints.
The Point-to-Multipoint network type has a 30 second hello and 120 second dead timer.

Comparison Table: OSPF Network Types

To summarize , we can enumerate the OSPF Network Types in the below table –

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MODE	PREFERRED TOPOLOGY	SUBNET ADDRESS	ADJACENCY	RFC or CISCO
Non-Broadcast	Fully Meshed	Same	Manual configuration DR/BDR elected	RFC
Broadcast	Fully Meshed	Same	Automatic DR/BDR elected	Cisco
Point-to-multipoint	Partial Mesh or Star	Same	Automatic No DR/BDR	RFC
Point-to-multipoint Non broadcast	Partial Mesh or Star	Same	Manual configuration No DR/BDR	Cisco
Point-to-point	Partial Mesh or star, using sub interface	Different for each subnet	Automatic No DR/BDR	Cisco

Download the table: OSPF Network Types

Continue Reading:

OSPF LSA Types The Ultimate Guide

OSPF Router Types: Detailed Explanation

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