OSPF Non-Broadcast Network Type over Frame-Relay

Thank you very much for answer. I’ll try to simulate this issue. Thank you for recommendation to set both router.

Best regards,
Marcin

1 Like
**R2:**
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Serial2/0
 ip address 192.168.123.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network non-broadcast
 serial restart-delay 0
 frame-relay map ip 192.168.123.1 102
 frame-relay map ip 192.168.123.3 103
 frame-relay map ip 192.168.123.2 102
!
router ospf 1
 network 1.1.1.0 0.0.0.255 area 0
 network 192.168.123.0 0.0.0.255 area 0
 neighbor 192.168.123.2
 neighbor 192.168.123.3
!


**R1**
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!interface Serial2/0
 ip address 192.168.123.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network non-broadcast
 serial restart-delay 0
 frame-relay map ip 192.168.123.1 102
 frame-relay map ip 192.168.123.3 103
 frame-relay map ip 192.168.123.2 102
!
router ospf 1
 network 1.1.1.0 0.0.0.255 area 0
 network 192.168.123.0 0.0.0.255 area 0
 neighbor 192.168.123.2
 neighbor 192.168.123.3


following is the Spoke 1, hub configuration . Hub,spoke1, spoke 2 ping each other. Why ip ospf neighbor
displays spoke 2 from spoke 1 as attempt state? debugging shows that r2 sends s ospf packet to spoke 1 and then mark it as dead. documentation and rene metnions to frame-relay map ip 192.168.123.1 201 br , the same and documentation mentions to boost the procedure of neighborship when there is no of it, so i am asking do i really have to use br on frame relay instruction in order to perform normal neighborship between the 2 routers or should i leave it as it is. Trying and the second choice(more logical - using br on frame relay instruction) since use broadcast to reply hub to spoke 2 packets but here the problem is on IP level, ospf not hearing ths UNICASTS hello packet to router 2. Could u please tell me wht will be the problem since i am able to ping each other router?

@lagapides @ReneMolenaar

Basic question :

At the beginning of this lesson it says :

“If you select the non-broadcast network type then OSPF will assume you are running a multi-access network”

I know Frame Relay is NBMA, but Ethernet also is a multi-access network , OSPF choose broadcast network type to its interfaces (despite you have a p2p link between two routers)
So NMBA it is not the only multi-access network … please could you shred some light on this issue ? Thanks in advance.

Hello Konstantinos

First of all, the Attempt state is a state that is only valid for manually configured neighbors in an NBMA environment, just like in your case. During the Attempt state, the router sends unicast hello packets every poll interval to the neighbor. If the state persists, that means that hellos have not been received from the neighbor within the dead interval.

More info on the Attempt state can be found here:

Now why is your topology stuck in Attempt state? Based on the configs you shared, I believe the problem is in the IP addressing. Both R1 and R2 have the same IP address on their serial interfaces: 192.168.123.1. Even if you fix that, another issue you will run into with OSPF is the fact that both R1 and R2 will have the same router ID. Remember, the router ID is chosen based on the highest loopback address. That address is the same on both devices. So I suggest you take a look at your addressing as well as your router ID to ensure that all configs are as they should be.

Let us know how you get along!

I hope this has been helpful!

Laz

Hello Juan

I understand how this may be confusing. I believe what Rene meant here was:

If you select the non-broadcast network type then OSPF will assume you are running a Non-Broadcast Multi-Access (NBMA) network.

Indeed Ethernet is a multi-access network. I will ask Rene to fix this and clarify it in the lesson.

Thanks for the input!

Laz

Hello Laz,
for the below drawing

If OSPF configured for all routers and assuming that link between R4 and R6 is failed and R4 not DR or BDR . How R4 will send update to R3 (the destination address for the update )? . Also How R4 will send update to R5 (Link between R4 and R5 is Point to point and what will be the destination address for the update )? the left side of the drawing are routers in the same broadcast network .(R1,R2,R3).

Appreciate your explanation in details

Thanks you

Hello Ramy

First of all it is important to realize that a DR/BDR election takes place per network segment only on multi-access segments. So in this case, the link between R4 and R6 does not have a DR/BDR election, and the link between R4 and R5 does not either. This is because, as you suggested, those links are point-to-point.

However, the link between R3 and R4 is I assume Ethernet, so between those two routers, R4 MUST be either a DR, or a BDR. Now DRs and BDRs will always listen on both 224.0.0.5 and 224.0.0.6. So if R4 is the BDR, it will send updates to 224.0.0.6. If R4 is the DR, it will send its updates to 224.0.0.5. In both cases, since R3 is always listening to both addresses, the update will reach it.

Now what if there was a third router on the segment and R4 was a DROTHER router? Then the update it would send would be to the 224.0.0.5 address, since it needs to send the update to the DR and BDR.

I hope this has been helpful!

Laz

Thanks for the explanation . excellent and clear one .