rules to live by...

• 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

• 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.

• 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
  • 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.

• 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.

• Loopback
  • The default OSPF network type; only available to loopback interfaces.
  • Advertises the interface as a host route; changeable by configuring the interface as point-to-point. 
  
  that's alot of shit to keep straight...