question about redistribution type 5 into nssa

[Dr.X]

hi ,

assume i have the topology below :

rip-----asbr1---------area(0)-process1----------asbr2------------nssa(area10)process2

now rip was redistributed into area0

the clear point is

now it will appear as type 5 , , and will not pass area 10 cause it is nssa

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now the unclear point

now  on asbr 2,

if i createf a route mapth and matched with it the external routers of ospf 1  and redistributed it into ospf process 2

will it be redistributed ?

my question is , does the asbr2 will convert the type 5 to 7 when it redistributed, or will reject it cause its type is 5

regards

[sukanyachavan]

Hi Ahmed,

Area 0 will send only LSA 3 ( default route only) in any NSSA.

And regarding your query on LSA 5 to LSA 7 translation, it is always 7 to 5 and never 5 to 7.

Regards,

Sukanya

[Dr.X]

hi

Sukanya ,

thanks for ur reply ,

i know that type 5 will never enter nssa ,

but if i make a redistribution of a routes which was type 5 , will it enter the nss as type 7 ?

or only the ospf routes that type 1 2 3 4  and other routing protocols such eigrp , rip  can be redistributed into nssa ?

anyway , i testes it on gns3 and it seems , type 5 cant be redistributed into nssa ,

hint i know that type 5 cant pass nssa , but my question was about redistributiong this type 5 and see if it will pass nssa

regards

[Giuseppe Larosa]

Hello Ahmed,

an OSPF NSSA area is intended to be used for those cases where:

A)-a stub area behaviour is desired with ABR nodes of the NSSA blocking all LSA type 5 and type 4 from entering the NSSA area.   LSA type 3 can be blocked if the area is a totally NSSA (no summary option in ABR area configuration)

B) - within the NSSA area there is a need to inject routes in the OSPF domain and they are injected as LSA type 7

ABR can translate LSA type 7 to LSA type 5 at area border depending on the propagation bit P in the LSA type 7.

The opposite conversion of backbone learned LSA type 5 to type  7 to be injected in the NSSA area does not happen because it is still a stub area in this direction.

So your test confirms the theory as expected.

Hope to help

Giuseppe