[nsp] OSPF NSSA

[John Pang]

Hi Oliver,

Thanks for the info.

One main reason why I ran NSSA was because R1 & R4 are
also redistributing static/connected routes and I
would like to limit the number of external routes that
enter R4 since R4 can basically just pass the traffic
to either R1/R2 and doesn't need to see everything
else that R1 redistributes.

Do you have any idea what could be done to achieve
this effect? Maybe some filtering in normal OSPF area
mode?

Best regards,

--- "Oliver Boehmer (oboehmer)" <oboehmer at cisco.com>
wrote:
> > 
> > I am currently trying out OSPF on the following
> lab
> > network:
> > 
> > R - R2 - R
> > 1 - R3 - 4
> > 
> > * R1 is connected to both R2 and R3 via router FE
> > ports
> > * R4 is connected to both R2 and R3 via router FE
> > ports
> > 
> > R1, R2 & R3 are in Area 0 while R2, R3 & R4 are in
> > Area 1.
> > 
> > In default configuration, R1 is able to see two
> paths
> > to R4 via either R2 or R3.
> > 
> > However, after I configured Area 1 as a NSSA, R1
> only
> > saw 1 path to R4 via R3.
> > 
> > Does anyone know why R1 only saw 1 path to R4 when
> > Area 1 is in NSSA mode? Is it possible for R1 to
> see
> > the same two paths to R4 when Area 1 is in NSSA
> mode?
> 
> This is expected behavior. There is only one
> Type7-Type5 translator with
> OSPF-NSSAs, so only one of the two NSSA-ABRs will
> announce the path to
> R4 into area 0. 
> 
> There is a "new" RFC 3101 which allows multiple
> translators, but support
> for this is still on our roadmap.
> 
> 	oli


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