Three Tier Campus Network OSPF Areas

[dm2020]

Hi All,

I am currently designing a new campus network that will consist of core, distribution and access layers. Core to distribution will be L3 with L2 between distribution and access. We will need ~ 10 distribution blocks, with each block consisting of 2 x C9500s in Stackwise Virtual.

I plan to place the core to core and core to distribution links in OSPF Area 0, however, is it still common practice to place the user/endpoint facing subnets in separate areas (areas 1 - 10 in the case) with the areas configured as stubs? I know that there were reasons to create a hierarchical design such as this for performance/scalability reasons, but with the current gen of hardware, is this still necessary and advised? 

Thanks,

[MHM Cisco World]

user faceing subnet as area 1 ....10 .
I dont get idea here if 
core-Agg is L3 
Agg-Access is L2 
then why you need different area for access ?
if you looking for summary then that great idea other than that I dont see benefit. 

https://www.geeksforgeeks.org/configuring-ospf-route-summarization-in-cisco/

[David Ruess]

Hello,

It certainly wouldn't hurt. You could manipulate routes better with segregated areas and less of a flooding domain. YOu could also tag/filter routes easier (still part of route manipulation). Also as you mentioned configuring the areas as STUB (if you use "no-summary" you ca just advertise a default route), further reducing the LSDB and routing table.

As for being efficient, if you only have 1 subnet per area then you aren't getting that much more bang for your buck. I'd say future route manipulation would be your biggest benefit here. If they are branch/remote sites then you may get a bit extra performance as the LSDB doesn't have to flood to the remote sites.

To your point I didn't even know that it was "common practice' to do it that way.

-David

[Richard Burts]

I am confused about the architecture that you describe and how you want to use OSPF. You tell us "Core to distribution will be L3 with L2 between distribution and access."  You tell us that core to distribution will be OSPF area 0, which makes sense. On the distribution you will run OSPF using area 0 on interfaces connecting to core. On the distribution the SVI connecting to access would not run a routing protocol since is it L2. So where would OSPF non zero areas be?