OSPF over Frame Relay - Quick Facts

OSPF is the most amazing protocol when it comes to the complexity in routing protocols. I personally like it more than BGP. OSPF has a different behavior on every media type. lets see how it responds to Frame Relay -


Also note the following points -

• Serial Interfaces are “multipoint” by default and are non-broadcast in nature, while point-to-point subinterfaces are broadcast in nature.
• Inverse ARP is “enabled” on all interfaces by default, including subinterfaces. In the case of “point-to-point” subinterfaces, inverse ARP is not used.
• When frame-relay inverse ARP is enabled, “broadcast” IP traffic will go out over the connection by default.
• IP split-horizon checking is “disabled” by default whenever the command “encapsulation frame-relay” is used.
• You have two different ways to configure the main physical interface in OSPF, non-broadcast (default) and broadcast.
• The default is non-broadcast and requires the frame-relay map command and the OSPF neighbor command.
• You have four different ways in which to configure “multipoint” subinterfaces in OSPF, non-broadcast (default), broadcast, p2mp and p2mp non-broadcast

For more information on OSPF over Frame Relay, You can refer to these documents -

• Cisco document titled, “Configuring and Troubleshooting Frame Relay”, document ID: 16563.
• Cisco document titled, “Initial Configurations for OSPF over Non-Broadcast Links”, document ID: 13690.
• Cisco document titled, “Initial Configurations for OSPF over Frame Relay Subinterfaces”, document ID: 13693.