Re: Type-7 to Type-5 translation issue

[Acee Lindem <[e-mail]>]

Santosh,
See inline.

Santosh Esale wrote:

>Hi Acee,
>            U mean i should check whether the ASBR path is via type-5
>capable area, and if its not USE NSSA external lsa for calculation and
>do the type-7 to type-5 conversion immediately.
>  
>
I'm saying that you should not use the AS-external-LSA if the path to
the ASBR is not
through a regular area (RFC 3101 uses the term Type-5 capable which I
really don't
like since we have descriptive names for the LSAs). If there is an
NSSA-LSA originated
by R1 it will be used by other routers in area 1 and R2 will do the
translation.

>I do agree with this...but we are doubling the LSP database size, how
>to slove it?
>  
>
You don't :^) In your example, R1 could attempt to flush all its
AS-external-LSAs prior
to converting to area 1 to a regular area. However, the network
administrator would have
to time the conversion such that the MAXAGE'ed AS-external-LSAs get
flooded to other
routers in area 1 prior to conversion (since AS scoped LSAs are not
flooded over NSSA
interfaces). In any case, they will not be used and it may be easier to
allow them to just
age out.

Hope this helps,
Acee


>Thanks
>Santosh
>
>On 5/16/05, Acee Lindem <[e-mail]> wrote:
>  
>
>>Hi Santosh,
>>
>>Whether or not R1 purges its AS-external-LSAs prior to area 1 being
>>coverted from a regular area to an NSSA is implementation specific.
>>However, the
>>timing of the conversion may be such that R1 is unable to purge them
>>from the
>>OSPF routing domain. In all cases, R1 should immediately originate
>>NSSA-LSAs
>>(type-7s) for redistributed routes. When R2 computes its external/NSSA
>>routes
>>it should not use R1's AS-external-LSA since its path to the ASBR is not
>>through
>>a regular area (see section 2.5 in RFC 3101).
>>
>>Hope this helps,
>>Acee
>>
>>Santosh Esale wrote:
>>
>>    
>>
>>>Hi guys,
>>>          Mine topology is as below-
>>>
>>>R1----Area 1 ------R2--------Backbone Area------R3
>>>
>>>Initially Area 1 was type-5 capabale area and i was redistributing RIP
>>>routes into area 1 on R1, so R2 and R3 have type-5 LSAs for all the
>>>RIP routes.Now i changed
>>>Area 1 to NSSA , So R1 is now orginating type-7 LSAs for all the RIP
>>>routes into area 1 with P-bit set.
>>>
>>>Now mine question is should R2 -
>>>
>>>1.     Prefer type 7 LSA over type-5 .
>>>Convert type-7 LSA into type-5 LSA  and flood into backbone, which
>>>aleardy have  type-5 LSAs for the same netwroks earlier orginated by
>>>R1(not yet flushed as it will remain in backbone for MAX AGE)
>>>(According to RFC 3101. section 2.5 stp 6 (e) ).
>>>
>>>Disadvantage: The LSP database size will be doubled till MAX AGE time.
>>>Advantage : simplicity
>>>
>>>2. Prefer type-5 over type-7 .
>>>Use type-5 LSA for calculating external routes till type-5 LSAs
>>>advertised by R1 exists in backbone(MAX Age) , and once type is
>>>flushed because of MAX age , USE type -7 now to calculate external
>>>routes , and translate at this point from type-7 to type-5(RFC 1587
>>>3.5 step 5)
>>>
>>>Advantage : LSP database size is small.
>>>Disadvantage: bit complex,but not much.
>>>
>>>3. or its Implementations Specific.
>>>
>>>Thanks in Advance
>>>
>>>
>>>
>>>
>>>      
>>>
>
>
>  
>