OSPF over NBMA

[banlan.chen]

Please help me to clarify this. Below is my understand for OSPF's behave on the NBMA environment. Thanks.

Default ospf network type:

Physical interface: Non-broadcast;

Point-to-point subinterface: Point-to-point;

Multipoint subinterface: Non-broadcast;

Neighborship: (use "show ip ospf neighbor" command)

Broadcast ----- Point-to-point: Full (But can't exchange LSAs each other, also no routes from other peer in the routing table. Don't know the reason.)

Broadcast ----- Non-broadcast: None

Broadcast ----- Point-to-multipoint: None

Non-broadcast ----- Point-to-point: None

Non-broadcast ----- Point-to-multipoint: Full (But can't exchange LSAs each other, also no routes from other peer in the routing table. Don't know the reason.)

Point-to-point ----- Point-to-multipoint: None

[mark-obrien]

Neighbors must be of the same ospf network type in order to become full neighbors, and therefore to exchange databases. Without the exchange of databases, the routers may not exchange LSAs. Also, the default OSPF network type on a multipoint sub-interface is point-to-multipoint.

[banlan.chen]

Hi Mark,

Thank you for your reply. I know neighbors' ospf network type must be same. But weird thing is that in my lab, I used multipoint subintface with Non-broadcast to a point-to-point subinterface with Point-to-multipoint, used "show ip ospf neighbor" I found the state is "full", but they couldn't exchange LSAs each other, also no routes from other peer in the routing table. I tried it couple of time, got same result. When I changed to same network type, it was working. I don't know the reason.

Banlan