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
Type 3: POINT-TO-POINT
- 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!!!
Type 4:
POINT-TO-MULTIPOINT
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.
Type 5: POINT-TO-MULTIPOINT
NON-BROADCAST
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
