Subject: Question about choosing NSSA ABR

From: Mani Devarajan <[email-masked]>
Date: Wed, 18 Sep 2002 12:36:09 -0700

Hi all,

RFC 1587:
 If this router has the highest router ID, it will be the
 one translating type-7 LSAs into type-5 LSAs for the NSSA, otherwise
 the translation algorithm should not be performed.

Why do we choose the NSSA ABR with the highest router ID to do
type-7 to type-5 LSA translation.

Why cant we choose a NSSA ABR which has the best cost path to
NSSA ASBR to do the type-7 to type-5 translation.

Thanks in advance,
Mani

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From: Acee Lindem <[email-masked]>
Date: Wed, 18 Sep 2002 16:52:17 -0400

> NSSA ASBR to do the type-7 to type-5 translation.

Mani,

The translated type 5 advertisements alway contain a forwarding
addresses. Hence, the cost from the translating ABR to the NSSA
ASBR is not important.

Thanks,
---
Acee

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From: Mani Devarajan <[email-masked]>
Date: Wed, 18 Sep 2002 14:14:23 -0700

> addresses. Hence, the cost from the translating ABR to the NSSA

 Acee,
  I understand that it makes no difference when the forwarding
  address is set in the type-5 LSA translated from type-7 LSA.

  If I assume that all NSSA ABRs have same address-range configuration,
  and the NSSA ABR with the highest routerid will do
  type7 to type5 translation and external network comes
  with in configured address range, it will set the forwarding
  address to 0.0.0.0 .  If the forwarding
  is 0.0.0.0, all the traffic for NSSA ASBR will be passing
  thorugh the NSSA ABR which did the type-7 to type-5 translation.
  In this case choosing the NSSA ABR with best cost path to the NSSA
ASBR
  will be a better option. Is my understanding correct?

Thanks,
Mani

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From: Acee Lindem <[email-masked]>
Date: Wed, 18 Sep 2002 17:34:31 -0400

>   will be a better option. Is my understanding correct?

In general, any time you aggregate routing information you have
the potential for a suboptimal routing. I don't necessarily view
introducing a corner case to handle this one as a better option.
You always have the choice of not configuring an NSSA address
range.

--
Acee