Simple OSPF-NBMA test question.

[news2010a]

I am testing OSPF configuration on NBMA networks. I have full IP connectivity between R6 to R3 and R6 to R4.

R4 and R3 should not ping each other by design.

I am aware of OSPF DR/BDR election issues on NBMA.

What I did:

I see R6 is a hub router. I configured R3 and R4 with 'ip ospf priority 0'  so they will never become DR/BDR. By doing that, I expected R6 to become DR.

Problem:

ospf neighbor relationship does not come up.

What am I missing? Please find attached configuration for R3, R6 an R4 and topology.

Requirements for the configuration:

You are required to use the point-to-multipoint OSPF network type on R6 S1/0/0.346.

                  ospf Neighbor commands cannot be used.

·        You are required to use the point-to-point OSPF network type on R3 and R4 serial interfaces.

·        Use only the physical interfaces for R3 and R4.

·        Disable the dynamic learning of Frame Relay PVCs.

[Mohamed Sobair]

Hi,

From the symptoms and I actually didnt look into your configuration, but please check  your (Hello and Dead) OSPF Intervals.

In a point to multi point Network , the hello is 30sec and the dead Interval is 120sec.

In a point to point OSPF Network, the hello is 10sec and the dead Interval is 120sec.

In order for OSPF neighborship to be successful, then the following has to match between neighbors:

1- Hello and Dead Interval.

2- AREA ID.

3- Stub Flag.

4- Subnet Mask.

HTH

Mohamed

[cadet alain]

Hi,

As mohamed said the hello/dead timers are different for these 2 ospf network types: p2mp is 30/120 and p2p is 10/40 so

modify timer on r6 to 10/40 and you'll see your neighbours come up.

Just a few remarks:

-p2mp and p2p ospf network types don't need no DR/BDR so your priority commands are useless

-why are you specifying lmi type on R4 it will auto discover it like the other routers otherwise if they differ from DCE to DTE then your PVC won't come up.

-on r6 why did you disabled inv arp on subinterface and not on physical interface?

If you still got problems with adjacency just send us output of :

show frame map

show frame pvc | i STATUS

show ip ospf interface brief

show run int

Regards.