From: Chuck Larrieu (chuck@xxxxxxxxxxxxx)
Date: Sun Dec 31 2000 - 03:00:06 GMT-3
OK, so there are four OSPF network types. Broadcast, non-broadcast,
point-to-point, and multipoint.
I've been hitting the basics due to a certain lack of understanding on my
part. Not through yet, but here are some things I found. Everything was done
on a frame relay full mesh among three routers ( DLCI to each of the other
two routers via a frame switch )
Serial links were all in the same /24 subnet.
OSPF network type = broadcast
The route indicating the frame is a single /24
OSPF network type = non broadcast ( cisco default for frame relay
interfaces )
The route in the table is a singe /24
OSPF network type = point-to-multipoint
Each interface address shows up as a host route ( /32 )
BTW I've been browsing RFC2328 ( OSPF ver 2 ) and it is stated within the
RFC itself that this is the way it is supposed to be. The RFC does not say
why.
On this latter, I got to wondering why. Inverse arp had already mapped IP
addresses to DLCI's Debug frame-relay packet is showing the layer two acting
the same way, both with broadcast and with multipoint types. I am unable to
reason this out with anything that makes sense to me. Having just browsed
the RFC, I'm thinking it has something to do with the way links are
identified within the OSPF process - sometimes as interface i.d.'s,
sometimes as RIDs.
The other puzzle I came across was the address used to forward OSPF
information. In every case I tried, I saw the OSPF packets going out using
the 224.0.0.5 multicast address. I never saw anything going to 224.0.0.6
DR / BDR address ) Nor did I see things going to a unicast address. ( I may
still have a combination or two to try still.)
Any case, for those who were discussing the reasons for the /32's in the
backbone, and how to get rid of them, both the RFC and my recent experiment
indicate that the /32's are part of the game and this is the way it is
supposed to be. Probably for god reason. Probably explained in one of the
several other OSPF RFC's which I will probably not get around to reading.
Chuck
----------------------
I am Locutus, a CCIE Lab Proctor. Xx_Brain_dumps_xX are futile. Your life as
it has been is over ( if you hope to pass ) From this time forward, you will
study US!
( apologies to the folks at Star Trek TNG )
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