Re: Idea behind DR copying the list of prefixes in the Link-LSA

[Paul Wells <pauwells at CISCO.COM>]

Hi Vishnu,

Only prefixes associated with the router itself (e.g. loopback 
interfaces) and attached stub (non-transit) network segments are 
advertised in the intra-area prefix LSAs associated with the router LSAs.

Prefixes associated with transit network segments are advertised in the 
intra-area prefix LSAs originated by the DR and associated with the 
type-2 LSA for that segment.  The way the DR finds out about the transit 
link prefixes is by looking at the link LSAs.

Regards,
Paul

vishnuvardhan B wrote:
> Hi,
> I am not able to understand the idea behind DR copying the list of 
> prefixes in the Link-LSA 
> RFC2740 sec 3.4.3.7:
>  Each Link-LSA associated with Link L is examined (these are in the
>       Designated Router's interface structure for Link L). If the Link-
>       LSA's Advertising Router is fully adjacent to the Designated
>       Router, the list of prefixes in the Link-LSA is copied into the
>       intra-area-prefix-LSA that is being built. 
> Since anyway all the routers describe about the prefixes in their own 
> intra-area prefix LSA's. So what is the advantage in advertising all the 
>
> prefixes in the link-lsa's by DR. Any replies will be most helpful.
> Reagards,
> Vishnu