OSPF NBMA network on multipoint subinterfaces

[mohammedmahmoud]

Hi all,

I know that the default OSPF network type for a Frame Relay multipoint subinterface or physical interface is NBMA, my question is even if i configured the frame-relay map command with the "broadcast" keyword would it still be NBMA ?

My second question is that I've found in my readings in some cisco documents, a recommendation to change the OSPF network type for multipoint subinterfaces and physical interfaces to "point-to-multipoint", in order not to require either a DR or to configure neighbors manually, how far is recommendation OK ?

regards,

Mohammed Mahmoud.

[dsweeny]

To avoid explicitly defining neighbors and controlling DR and BDR election on NBMA networks, perform these options:

Use point-to-point subinterfaces.

Configure the OSPF network type as point-to-multipoint.

Configure the network type as broadcast.

The following URL should help you:

http://www.cisco.com/warp/public/104/3.html#11.0

[sundar.palaniappan]

1) I know that the default OSPF network type for a Frame Relay multipoint subinterface or physical interface is NBMA, my question is even if i configured the frame-relay map command with the "broadcast" keyword would it still be NBMA ?

Yes, it would still be NBMA. Adding the broadcast keyword in the frame relay map only enables broadcasts to traverse the PVC and doesn't change the default OSPF interface type.

2) My second question is that I've found in my readings in some cisco documents, a recommendation to change the OSPF network type for multipoint subinterfaces and physical interfaces to "point-to-multipoint", in order not to require either a DR or to configure neighbors manually, how far is recommendation OK ?

It depends on your topology. While NBMA setup may be a good choice for meshed network point-to-multipoint might be a good choice for hub-and-spoke topology. Again, it's knowing what options are available is the important thing as far as choosing the right network type is concerned.

HTH

Sundar