Re: Section 16.2 of RFC2328 and ABR's behaviour

[Srinivas Goli <goli at LAURELNETWORKS.COM>]

> -----Original Message-----
> From: Mailing List [mailto:OSPF at PEACH.EASE.LSOFT.COM] On 
> Behalf Of Acee Lindem
> Sent: Tuesday, February 14, 2006 5:18 PM
> To: OSPF at PEACH.EASE.LSOFT.COM
> Subject: Re: Section 16.2 of RFC2328 and ABR's behaviour
> 
> Srinivas Goli wrote:
> 
> >Folks,
> >
> >Section 16.2 states the following
> >
> >    16.2.  Calculating the inter-area routes
> >
> >        The inter-area routes are calculated by examining 
> summary-LSAs.
> >        If the router has active attachments to multiple areas, only
> >        backbone summary-LSAs are examined.  Routers attached to a
> >        single area examine that area's summary-LSAs.  In 
> either case,
> >        the summary-LSAs examined below are all part of a 
> single area's
> >        link state database (call it Area A).
> >
> >>From this it is clear that the an ABR will only examine the summary 
> >>LSAs
> >from the backbone area. This is done to avoid the counting 
> to infinity 
> >problem since exchanging routes between areas is done using Distance 
> >Vector mechanisms.
> >
> >Now some of vendors seems to skip this check i.e examining 
> summary LSAs 
> >from all attached areas. Can any one explain why this would be 
> >considered useful, assuming this is done intentionally.
> >  
> >
> Hi Srinivas,
> See RFC 3509.
> Thanks,
> Acee
> 
Hi Acee,

I had looked at RFC3509 as possible explanation of what I saw but the
particular case I am looking at is a router with two actively attached
areas both of which are non backbone areas. The router would identify
itself as ABR by setting B bit in the router-lsa. The router also
re-advertises the summary LSAs in one area into the other areas. 

Thanks, 

 
> >Regards,
> >
> >  
> >
> 
>