I really need an expert opinion on this. What is the difference between these two topologies?
I understand LSA type 1,2,3 are area specific. Why should I change the Area numbers because the areas 1 are not directly connected.
Can someone describe this.
Rick, what I had in mind was something like two area 1 ABRs using a summary for the complete address range that covered all area 1 addresses. However, I also agree with you if each partitioned part of area 1 only generated a summary for its part of area 1, then area 0 should be able to direct traffic to the correct ABR.
I would caution the original poster, that avoiding this type of design might be more than just "best practice". Intentionally designing partitioned OSPF areas is the type of thing that often comes back later that makes for new problems. This often is especially true when you need to mix different vendor equipement.
If you read RFC2328's "Routing in the Autonomous System takes place on two levels, depending on whether the source and destination of a packet reside in the same area (intra-area routing is used) or different areas (inter-area routing is used). In intra-area routing, the packet is routed solely on information obtained within the area; no routing information obtained from outside the area can be used. This protects intra-area routing from the injection of bad routing information." could be implemented such that area 1 traffic in one partition could not transit area 0 to reach the other partition.
I was going to suggest, you might also want to post "WAN, Routing and Switching: ASK THE EXPERT INTERIOR DYNAMIC ROUTING PROTOCOLS", but I see you've already posted there too.