OSPF Designing Help

[Nirmalbang]

Hi,

I am designing a network, protocol used OSPF. Attached is the diagram. My query is

1) On site A I have two network behind a l3 switch 172.16.x.x and 172.26.x.x in area 3.3.3.3

2) On Site B I have two network behind a l3 switch 172.30.x.x and 172.20.x.x in area 2.2.2.2 

Traffic from Site A to Site B takes proper route which is 10.48.48.0 and 10.221.221.4 but traffic from Site B to Site A gets routed from DC location which i don't want. What i want is the traffic from Site B to Site A should also go thru 10.48.48.0 and 10.221.221.4. Any help in this will be highly appreciated.

Attached is the network diagram with the Interface IP and areas 

[rais]

You topology is a full mesh, yet there are several OSPF areas defined. Since you have full mesh, your requirement of using direct connectivity is achievable by placing all sites into a single ospf area.

For multiple OSPF areas, the flow of traffic between non-backbone area will be thorough backbone, coz that's how the routing information is disbursed. 

Thanks.

[Nirmalbang]

Hi Rais / Joseph,

Thanks for the revert. Is it safe to put all sites in single area. I mean will it not flood all sites upon changes.Though I done have big routing table. approx there might be 70 to 80 routes in the routing table of my l3 switches. Hope i am making sense. 

[ahmedshoaib]

Hi;

It's total depend on your network (how many routes & how many l3 devices running OSPF). If you have small network you can put all the l3 devices in a single area. 70 to 80 routes routing table is not a big routing table. And you can also configure OSPF as multi area environment. Be remember once you configure muti-area ospf your all area should be connected via Area 0.

Yes if any change in routing information is flooded to all routers in the same area.

Thanks & Best regards;

[Joseph W. Doherty]

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Posting

Like Ahmed write, 70 or 80 routes isn't big.

Yes, LSAs flood through out their area, not only for changes, but also for reoccuring refreshes.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

As Rais mentioned, OSPF routes between areas using area zero.  So as Sites A and B are in different areas, the question might not be why Site B traffic doesn't use the Site A <> Site B link, but why Site A does for traffic to Site B.

There's not enough detail on your diagram to explain how traffic should route between those two sites.

If you have an OSPF router with multiple area links, but its not an ABR, its local route table can have information from the different areas, and it may route to a destination that it sees in a different area from the source area, not following OSPF routing topology rules.