Subject: [OSPF] RFC 3101 ASE address range LSA

From: Sandeep <[email-masked]>
Date: Wed, 26 Sep 2007 11:11:28 +0800

Hello Pat,

Some questions about RFC 3101 [OSPF NSSA] ASE address range LSA.

Question 1: For asbr range Type-5 LSA, should we consider both the routes
(one from OSPF_NSSA for translation and the other locally sourced route)
with same preference and select route based on type and cost only or should
there be a preference to OSPF route over locally sourced route?

Consider both RTA and RTB import static route x.x.x.x/32. Configure asbr
range x.0.0.0/8 on RTB.

x.x.x.x/32        x.x.x.x/32

cost = 3           cost = 1

type = 2           type = 1

 ||                  ||

 ||                  ||

 V     Area 1         V      Area 0

RTA------------------RTB-------------RTC

        NSSA          (ABR)

Routes on RTB,

x.x.x.x/32 cost = 3 type 2 OSPF    [for 7to5]

x.x.x.x/32 cost = 1 type 1 static [locally sourced]

ASE LSA: x.0.0.0/8 cost = ? type ?

The description in RFC3101 section 3.2.

Section 3.2

  "Note that it is possible for a Type-5 LSA generated by translation to

   supplant a Type-5 LSA originating from a local OSPF external source.

   Future reoriginations of the locally sourced Type-5 LSA should be

   suppressed until the Type-5 LSA generated by translation is flushed."

Section 3.2 (3) For Type-7 address range,

         "The path type and metric of the Type-7 address range is

          determined from the path types and metrics of those

          translatable Type-7 LSAs that best match the range plus any

          locally sourced Type-5 LSAs whose network has the same

          [address,mask] pair.  If any of these LSAs have a path type of

          2, the range's path type is 2, otherwise it is 1."

Am I missing something!!

Thanks & Regards,

Sandeep

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