OSPF over Frame-Relay, focus on Network Types

Don't forget that in Frame-Relay "broadcast" is defined ONLY DIRECTLY HUB AND A SPOKE, ON BOTH SIDES of the pvc!!! What this does is tell the routers “Hey if you have any broadcast messages, go ahead and send them down this DLCI as a unicast” So basically it is a way to send broadcast messages on a non-broadcast medium. Don't include "broadcast" between the SPOKEs, as the Hellos won't be able to traverse the HUB.

Type 1: NON-BROADCAST - use "neighbor" command on HUB to use UNICAST for OSPF
OSPF uses Multicast, which Router considers to be a kind of Broadcast. Due to the non-broadcast nature of Frame-Relay it can be assumed that this is the DEFULT OSPF network type over FR.
- Set the OSPF Priority to 0 on all the SPOKEs, so HUB is elected as the DR, and SPOKEs neither DR nor BDR
- Non-broadcast network type in OSPF uses “slow” timers meaning 30 second hello and 120 second dead-time. Here it will not affect us, as all neighbor types match.

Type 2: BROADCAST - two important things:
- As BROADCAST is meant to be FASTER timers are 10/40 seconds by default
- Include the "broadcast" when mapping DLCI to IP. Also set the SPOKEs OSPF Priority to 0, we don’t want them to be DR

- Really simple, POINT-TO-XXX (P2P or P2MP) does not do the DR/BDR election
- Timers 10/40 seconds
TIP: When doing a HUB-AND-SPOKE, configure Point-to-Multipoint on a HUB, and ADJUST THE TIMERS!!!

No DR, no "neighbor" command. Slow timers (120/30 seconds). "broadcast" is mandatory on FR Mappings!!!
HUB will just advertise the learned routes from ONE SPOKE to the other, like if it were the DR.
!!!HUB must have .multipoint Sub-interface, while on SPOKES you can do .multipoint or Physical Interface.

Cisco Proprietary, like P2MP, with NO BROADCASTS ALLOWED! Timers are still slow, 30 and 120 Seconds.
Next hop is ALWAYS the router you are directly connected to.

(config-if)#ip ospf network point-to-multipoint non-broadcast

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