NSSA

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Which of the following OSPF routes are supported by the Not-So-Stubby-Area
(NSSA) type? (Select three)

A. O

B. O IA

C. O N2

D. O* N2

E. O* IA



I would go with A, C, D

What do you guys think?




Re: NSSA


A, C, D here also




Re: NSSA


NSSA Blocks Type 4 and 5 LSAs.
So the answer should be O, OIA, N2 - A, B, C
As OSPF intra Area (O) , OSPF inter area (OIA) and external routes (N2)
won't be blocked.

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Re: NSSA


OK.  Looks like I need to do some review on that.

But if "O N2" is correct, then "O*N2" should also be correct.  The latter is
generated by a default-information originate by a member router within the
NSSA area.

Robert

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Re: NSSA


I labbed this one up with an AREA 1 NSSA DEFAULT-INFORMATION-ORIGINATE on
the ABR bordering areas 0 and 1.

Both LSA 3 and 4 show up as O IA so some of these may be blocked and any
type of O E would be blocked as LSA 5 and would not show up in the Area 1
(excluding the ABR).

O, O IA, O N2, O*N2 are all seen in NSSA area 1.

Hmmmmmm...  it seems to me that the word "support" is rather ambiguous.

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Re: NSSA


Friends,

In OSPF the nssa blocks only type 5 lsa and instead allows type 7 lsa.
But nssa nosummary blocks type 3, type 4 and type 5 and allows type 7
instead.

Hence in nssa the allowed lsa are
type 1
type 2
type 3
type 4
and type 7

therefore the answer to the above question should be,

a, b, c

A. because its type 1 and type 2 lsa

b because, type 3 and type 4 lsa are allowed

c because, type 7 is used instead of type 5

d and e are  incorrect because * indicates a default candidate but
since its a nssa area not nssa nosummary there will be no default
candidate as type 1 to 4 are allowed and type 5 is replaced by type 7.

regards,
niitin



Re: NSSA


Yes, I mis-spoke about LSA 4, they are indeed allowed under NSSA.  A,B,C is
likely the expected answer.  However, O*N2 doesn't require NO-SUMMARY and is
thus supported under NSSA.  Since LSA 4s are not blocked, O*N2 would
probably not considered in the top 3 answers.

Robert

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