Clarification on OSPF, point-to-multipoint network type

Answered Question
Aug 30th, 2009
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I just want to make sure I understand this correctly:


I know that, when configuring OSPF, if interface type is "point-to-multipoint" for example, no DR/BDR and no neighbor command is required for proper OSPF operation.


I just want to confirm that it is true even when I am configuring "point-to-multipoint" on Frame-Relay, which is NBMA?


Correct Answer by Edison Ortiz about 7 years 6 months ago

When configuration OSPF, if the OSPF Network Type (not the interface) is point-to-multipoint, you won't have DR/BDR election in the segment and no neighbor command is required.


Frame-Relay does not have a 'point-to-multipoint' interface, it has 'multipoint' or 'point-to-point'


R1(config)#int s0/0.111 ?

multipoint Treat as a multipoint link

point-to-point Treat as a point-to-point link


and enabling OSPF on a multipoint subinterface produces the same result as enable OSPF on the main interface under frame-relay, the OSPF network type will be Non-broadcast.


R1#sh run int s0/0.123

Building configuration...


Current configuration : 130 bytes

!

interface Serial0/0.123 multipoint

ip address 192.168.123.2 255.255.255.0

frame-relay map ip 192.168.123.3 203 broadcast

end


R1#sh ip os int

Serial0/0.123 is up, line protocol is up

Internet Address 192.168.123.2/24, Area 0

Process ID 1, Router ID 192.168.123.2, Network Type NON_BROADCAST, Cost: 64


HTH,


__


Edison.

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Correct Answer
Edison Ortiz Sun, 08/30/2009 - 19:52
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When configuration OSPF, if the OSPF Network Type (not the interface) is point-to-multipoint, you won't have DR/BDR election in the segment and no neighbor command is required.


Frame-Relay does not have a 'point-to-multipoint' interface, it has 'multipoint' or 'point-to-point'


R1(config)#int s0/0.111 ?

multipoint Treat as a multipoint link

point-to-point Treat as a point-to-point link


and enabling OSPF on a multipoint subinterface produces the same result as enable OSPF on the main interface under frame-relay, the OSPF network type will be Non-broadcast.


R1#sh run int s0/0.123

Building configuration...


Current configuration : 130 bytes

!

interface Serial0/0.123 multipoint

ip address 192.168.123.2 255.255.255.0

frame-relay map ip 192.168.123.3 203 broadcast

end


R1#sh ip os int

Serial0/0.123 is up, line protocol is up

Internet Address 192.168.123.2/24, Area 0

Process ID 1, Router ID 192.168.123.2, Network Type NON_BROADCAST, Cost: 64


HTH,


__


Edison.

Peter Paluch Sun, 08/30/2009 - 20:07
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  • Cisco Employee,

Hello,


Agree absolutely.


Marlon, if you want to read something about the theoretical background regarding the network types, I have described them earlier in this thread:


http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=WAN%2C%20Routing%20and%20Switching&topicID=.ee71a06&fromOutline=&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.2cd43a87


A lengthy reading, I admit, but it might be of interest to you.


Best regards,

Peter


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