From: hcb@gettcomm.com
Date: Sun May 21 2006 - 19:27:26 ART
Quoting gigi.ccie@gmail.com:
> http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2003.htm#wp3618
>
> Now this is a proper reference to this type of question. But as you can see,
> it does not quite answer the question.
>
> Step 1 Define your structure (identify areas and allocate nodes to areas).
>
> Step 2 Assign addresses to networks, subnets, and end stations.
"Networks"? That's an obsolete term, in that it refers to classful addressing.
At the CCIE level, always think classless unless there is a specific
requirement to deal with classfulness -- and I doubt there will be.
>
> In the network illustrated in , each area has its own unique NIC-assigned
> address.
Again, this appears to be an obsolete reference. The NIC hasn't been assigned
address space for years. Address assignments come from regional internet
registries (ARIN, RIPE NCC, APNIC, LACNIC, AfrNIC) or, in some cases,
lower-level registries.
>These can be Class A (the backbone in ), Class B (areas 4 and 6), or
> Class C (Area 5). The following are some clear benefits of assigning separate
> address structures to each area:
More correctly, /8, /16, and /24.
>
> Address assignment is relatively easy to remember.
>
> Configuration of routers is relatively easy and mistakes are less likely.
>
> Network operations are streamlined because each area has a simple, unique
> network number.
>
> The main drawback of this approach to address assignment is that it wastes
> address space.
To an extent that if you went to an address registry and asked for unique
addresses based on a classful structure, they might laugh as they said NO.
>If you decide to adopt this approach, be sure that area border
> routers are configured to do route summarization. Summarization must be
> explicitly set; it is disabled by default in OSPF.
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