Non-Broadcast

Non-Broadcast
A non-broadcast environment requires that all OSPF neighbors be manually configured. This is
the default setting for physical interfaces with Frame Relay encapsulation, as well as for their
point-to-multipoint subinterfaces. By manually configuring each neighbor, OSPF knows exactly
which neighbors need to participate and which neighbor is identified as the DR. Also, communication
between neighbors is done via unicast instead of multicast. This configuration also requires
a full mesh and has the same weakness as the broadcast environment.
For non-broadcast networks the default Hello interval is 30 seconds and the Dead interval
is four times the Hello interval, 120 seconds. Non-broadcast multi-access networks do elect a
DR and BDR, due to their multi-access nature. In order to set which router you want as the DR,
you must set the priority in the neighbor statement to elect the neighbor as the DR. In order
to manually configure who your neighbors are, the following command must be entered in
router configuration mode for the selected OSPF process:
neighbor ip_address
ip_address = the ip address of the neighbor.
158 Chapter 5  OSPF Operation in a Single Area
If you would like to set the priority of this router to become the DR, you will need to append
the priority of the neighbor:
neighbor ip_address priority value
ip_address = the ip address of the neighbor.
value = the priority value of the neighbor. The value will range
from 0 to 255, with 0 meaning a router will never become the DR
and 255 being the best setting for a router to become the DR.
To manually configure a network type of non-broadcast, you need to enter the ip
ospf network non-broadcast command in interface configuration mode for the selected
interface.