OSPF broadcast mode w/ inverse-arp

Unanswered Question
Jul 5th, 2007

I am seeing some behavior out of OSPF in non_broadcast mode that I would not expect. I haven't identified any neighbors on any interfaces, yet the spokes are forming full adjacencies with the hub. I do have inverse-arp enabled on my frame switch and I suspect that inverse-arp is 'enabling' this behavior. Can you please explain the what and the why of what I am seeing?

------------------ HUB -----------------

interface Serial1/0

description *** to Frame Switch S5 ***

ip address 172.31.11.4 255.255.255.0

encapsulation frame-relay

no fair-queue

router ospf 1

log-adjacency-changes

network 172.31.11.0 0.0.0.255 area 0

------------------Spoke1----------------

interface Serial0/0

ip address 172.31.11.1 255.255.255.0

encapsulation frame-relay

frame-relay lmi-type cisco

router ospf 1

log-adjacency-changes

network 172.31.11.0 0.0.0.255 area 0

-----------------Spoke2-----------------

interface Serial0/0

ip address 172.31.11.2 255.255.255.0

encapsulation frame-relay

end

router ospf 1

log-adjacency-changes

network 172.31.11.0 0.0.0.255 area 0

spoke2#show ip ospf nei

Neighbor ID Pri State Dead Time Address Interface

172.31.11.4 1 FULL/BDR 00:01:48 172.31.11.4 Serial0/0

spoke2#show ip ospf int

Serial0/0 is up, line protocol is up

Internet Address 172.31.11.2/24, Area 0

Process ID 1, Router ID 172.31.11.2, Network Type NON_BROADCAST, Cost: 64

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sundar.palaniappan Thu, 07/05/2007 - 14:35

Hi

Just wondering did you have neighbor statements earlier then subsequently removed it. I have seen routers use the cached neighbor info to form ospf adjacency.

HTH

Sundar

jdevoll Thu, 07/05/2007 - 15:56

Actually yes, I did have the neighbor statements listed previously. I'll re-load everything and see if I end up with the same behavior.

Edison Ortiz Thu, 07/05/2007 - 15:29

Let's see the 'show frame map' and 'show ip os int bri' command from all routers involved.

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