Subject: OSPFv3 Questions

From: query OSPF <[email-masked]>
Date: Fri, 6 Feb 2004 05:43:06 -0000

Hi,

I have couple of questions.
1. What is the purpose of options field in Router-LSA? This options information can be collected from the hello packet also.

2. If a router generate two router-LSA and then in the case of a mismatch of options field in the two Router-LSA, then according to rfc2740, LSA with lowest link state ID take precedence, Why?

regards

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From: Michael Barnes <[email-masked]>
Date: Thu, 5 Feb 2004 23:24:06 -0800

On 02/06/2004 at 05:43 AM, query OSPF <[email-masked]> said:

>1. What is the purpose of options field in Router-LSA? This options
>information can be collected from the hello packet also.

The Router-LSA is flooded throughout an area. This way, all of the routers
in the area will know what options the router supports, not just those
which receive the Hello packets. This is particularly important because
some of the bits in the Router-LSA's options field, such as the v6 bit,
are required during the SPF calculation.

>2. If a router generate two router-LSA and then in the case of a mismatch
>of options field in the two Router-LSA, then according to rfc2740, LSA
>with lowest link state ID take precedence, Why?

If the router's options change only one of the Router-LSAs needs to be
re-originated. This way all of the routers know which of the Router-LSAs
will have the correct options bits.

Regards,
Michael