LSA aging with DNA Bit in normal ospf

[anuruddha-bhadoria]

Hi team ,

I just wanted to ask why we do not support dna bit in normal ospf ?As of now LSA refreshes in every 30 minutes in order to maintain the LSDB but in case of virtual link we use DNA(DoNotAge) in order to suppresses the periodic hello and lsa Refresh 

so my question is same why we can not support this in normal ospf such that once the database re exchange then there is not any advertisement of lsa refresh and when there is a topology change then LSA will get refresh 

[MHM Cisco World]

Dna is defualt with virtual link

But you can also use by flood reduction.

https://www.cisco.com/en/US/docs/ios/12_1t/12_1t2/feature/guide/dt_ospff.html

MHM

[anuruddha-bhadoria]

Can you explain this in detail as I have gone through that link but it is bit confusing 

does flood reduction also uses DNA how it works ? 

[MHM Cisco World · Accepted solution]

Yes it use it 

"" With OSPF flood-reduction, the unwanted flooding is achieved by setting the DoNotAge (DNA) bit in the LSAs,""

https://lpmazariegos.com/tag/ospf-flood-reduction/

MHM

[Joseph W. Doherty]

As @MHM Cisco World describes, Cisco provides a feature you can DNA in normal OSPF, but should you?  Also keep in mind some of these features were created when WAN links bandwidths might be 64 Kbps, or less, and the processing resources were much constrained, compared to later hardware (like the EIGRP feature specifying max amount of interface bandwidth allowed to be used by EIGRP).

If the default 30 minute LSA refresh is a bandwidth/CPU consideration, today, I would wonder what the heck kind of OSPF architecture you're running.  (There's reason for OSPF areas, and their stub and summarization features.)