From: Jason Guy \(jguy\) (jguy@cisco.com)
Date: Sat Jun 16 2007 - 09:47:50 ART
Hi Group,
As soon as I thought I had a grasp of this, I found a scenario that I
could not explain. I have a Frame-relay hub and spoke, where the hub
uses the main interface and the spokes are required to use
subinterfaces.
Now, the main interface will default to NONBROADCAST. Knowing this, I
thought I would use a multipoint subinterface which also defaults to
NONBROADCAST. I set the ospf priority to 0 on the spokes. This made
sense, the network types match, and all is good.
However, I fought with this, and finally determined it was not going to
work. The OSPF came up, I had routes, but I could not ping spoke to
spoke. So I decided to try a point to point subinterface which defaults
to POINT2POINT, and changed the ospf network type to NONBROADCAST. The
links came up and I could ping.
My question is why? What is different at the frame-relay layer between
the MP and P2P subinterface and how OSPF sees this differently? I would
think if frame relay is pinging, and the Hub is the DR, either
subinterface should send the packet to the hub. The fact that MP
defaults to the correct seems a likely choice for this.
The one interesting thing I see in the sh ip ospf neigh output is the
way the neighbors appear. There is a FULL to the hub and ATTEMPT to the
other spoke.
Neighbor ID Pri State Dead Time Address Interface
10.2.2.2 1 FULL/DR 00:01:39 11.1.1.2
Serial0/0.1
N/A 0 ATTEMPT/DROTHER - 11.1.1.3
Serial0/0.1
Thanks,
Jason
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