Open Shortest Path First (OSPF) - Router Alley

OSPF v1.31 – Aaron Balchunas
8
Configuring OSPF Network Types (continued)
The default OSPF network type for Point-to-Multipoint Frame Relay is still
Non-broadcast Multi-access Network (NBMA). However, OSPF supports
an additional network type called Point-to-Multipoint, which will allow
neighbor discovery to occur automatically. To configure:
Router(config)# interface s0
Router(config-if)# encapsulation frame-relay
Router(config)# interface s0.2 multipoint
Router(config-if)# frame-relay map ip 10.1.1.1 101 broadcast
Router(config-if)# ip ospf network point-to-multipoint
Additionally, a non-broadcast parameter can be added to the ip ospf network
command when specifying point-to-multipoint.
Router(config)# interface s0
Router(config-if)# encapsulation frame-relay
Router(config)# interface s0.2 multipoint
Router(config-if)# frame-relay map ip 10.1.1.1 101
Router(config-if)# ip ospf network point-to-multipoint non-broadcast
Router(config)# router ospf 1
Router(config-router)# neighbor 10.1.1.1
Notice the different in configuration. The frame-relay map command no
longer has the broadcast parameter, as broadcasts and multicasts are not
allowed on a non-broadcast network.
Thus, in the OSPF router configuration, neighbors must again be manually
specified. Traffic to those neighbors will be unicast instead of multicast.
OSPF network types must be set identically on two “neighboring” routers,
otherwise they will never form an adjacency.
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