Hi Gaurav,
I'd like to say this is not applicable to OSPFv3 since it is one of those
optimizations that I think is more pain and complexity than it is worth (not to
mention the potential convergence delay if one ASBR becomes unreachable).
However, the intent is definitely that this behavior is carried over to OSPFv3.
Thanks,
Acee
On Jun 5, 2012, at 1:26 PM, Gaurav Agrawal wrote:
Hi Acee,
I was not referring to NSSA capabilities. I was referring to
Functionally equivalent LSAs, which applies to AS-external LSAs as well. There
is no mention or reference in OSPFv3 RFC:
It is defined for OSPFv2 in section 12.4.4.1 RFC 2328,
RTA and RTB would originate the same set of AS-
external-LSAs. These LSAs, if they specify the same
metric, would be functionally equivalent since they
would specify the same destination and forwarding
address (RTX). This leads to a clear duplication of
effort. If only one of RTA or RTB originated the
set of AS-external-LSAs, the routing would remain
the same, and the size of the link state database
would decrease. However, it must be unambiguously
defined as to which router originates the LSAs
(otherwise neither may, or the identity of the
originator may oscillate). The following rule is
thereby established: if two routers, both reachable
from one another, originate functionally equivalent
AS-external-LSAs (i.e., same destination, cost and
non-zero forwarding address), then the LSA
originated by the router having the highest OSPF
Router ID is used. The router having the lower OSPF
Router ID can then flush its LSA. Flushing an LSA
is discussed in Section 14.1.
Thanks,
Gaurav
On Tue, Jun 5, 2012 at 9:55 AM, Acee Lindem
<[email protected]<mailto:[email protected]>> wrote:
Hi Gaurav,
Yes - you can assume the same NSSA logic. From the RFC 5340 Abstract:
All of OSPF for IPv4's optional capabilities, including demand
circuit support and Not-So-Stubby Areas (NSSAs), are also supported
in OSPF for IPv6.
The NSSA-LSA description was missing from RFC 2740 and added to RFC 5340. Also
from RFC 5340:
3.3. NSSA Specification
This protocol feature was only partially specified in RFC 2740. The
level of specification was insufficient to implement the function.
This document includes an NSSA specification unique to OSPFv3. This
specification coupled with [NSSA] provide sufficient specification
for implementation. Refer to Section 4.8.5, Appendix A.4.3,
Appendix A.4.8, and [NSSA].
Thanks,
Acee
On Jun 5, 2012, at 4:51 AM, Gaurav Agrawal wrote:
Hi,
I had a question about functionally equivalent AS-External LSA/NSSA LSA for
OSPFv3. There is no mention in RFC 5340 or RFC 2740 in this regard. RFC 2328
and RFC 3101 provides details in context of OSPFv2. Can the same logic be
extended for OSPFv3 as well?
Thanks,
Gaurav
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