Re: area 1 nssa default-information-originate no-summary

Good Afternoon Tom,

After labbing it up we can see what happens when we use the following:

I have R2 and R6 in this example in area 3 NSSA, R6 is the ABR and is
configured with the following:

 area 3 nssa default-information-originate

If I look at the following routing table on R2:

I get the following:

R2#show ip route ospf
O N2 204.12.2.0/24 [110/20] via 110.1.100.6, 00:02:51, Serial0/0
O N2 204.12.3.0/24 [110/20] via 110.1.100.6, 00:02:51, Serial0/0
O N2 204.12.4.0/24 [110/20] via 110.1.100.6, 00:02:51, Serial0/0
O N2 204.12.5.0/24 [110/20] via 110.1.100.6, 00:02:51, Serial0/0
     110.0.0.0/8 is variably subnetted, 10 subnets, 3 masks
O IA 110.1.6.1/32 [110/65] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.0.6/32 [110/64] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.4.1/32 [110/129] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.5.1/32 [110/130] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.3.1/32 [110/129] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.1.1/32 [110/130] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.0.0/24 [110/192] via 110.1.100.6, 00:02:51, Serial0/0
O IA 110.1.145.0/24 [110/129] via 110.1.100.6, 00:02:51, Serial0/0
O N2 192.6.6.0/24 [110/20] via 110.1.100.6, 00:02:51, Serial0/0
     150.100.0.0/24 is subnetted, 2 subnets
O N2 150.100.1.0 [110/20] via 110.1.100.6, 00:02:53, Serial0/0
O*N2 0.0.0.0/0 [110/1] via 110.1.100.6, 00:02:53, Serial0/0

This tells me that not only it generates a default route but also
advertises Interarea Routes.

Now let me go back to R6 and take out the default information originate.
Now I will just use the no-summary on R6.

O N2 204.12.2.0/24 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
O N2 204.12.3.0/24 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
O N2 204.12.4.0/24 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
O N2 204.12.5.0/24 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
O N2 192.6.6.0/24 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
     150.100.0.0/24 is subnetted, 2 subnets
O N2 150.100.1.0 [110/20] via 110.1.100.6, 00:00:56, Serial0/0
O*IA 0.0.0.0/0 [110/65] via 110.1.100.6, 00:01:01, Serial0/0

Now I just have the default route but not the InterArea Routes.

Now I will go back to R6 put default-information-originate along with
the no-summary

R2#show ip route ospf
O N2 204.12.2.0/24 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
O N2 204.12.3.0/24 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
O N2 204.12.4.0/24 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
O N2 204.12.5.0/24 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
O N2 192.6.6.0/24 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
     150.100.0.0/24 is subnetted, 2 subnets
O N2 150.100.1.0 [110/20] via 110.1.100.6, 00:00:19, Serial0/0
O*IA 0.0.0.0/0 [110/65] via 110.1.100.6, 00:00:19, Serial0/0
R2#

Same output as before with just the no-summary option configured.

So to answer your question, based on observation there is no need to
have default-information-originate when you have the no-summary
command configured.

Regards,
John

On 4/14/12, Marko Milivojevic <markom_at_ipexpert.com> wrote:
> Today, it makes no sense. In the past (I recall 12.2(33)SXD) when they were
> both used a Type 3 default was suppressed and only Type 7 default route was
> generated.
>
> --
> Marko Milivojevic - CCIE #18427
>
> :: This message was sent from a mobile device. I apologize for errors and
> brevity. ::
>
> On Apr 13, 2012, at 19:47, Tom Kacprzynski <tom.kac_at_gmail.com> wrote:
>
>> Hello,
>> Does this command make sense? In what situation would you use no-summary
>> and default-information-originate at the same time? With the no-summary
>> option a LSA Type 3 default route is generated, so what would the
>> default-information-originate command do? I tried it in a lab and it only
>> generated a default LSA Type 3 based on the no-summary option.
>>
>> Can anyone think of a scenario where this would ever work or be used?
>>
>> Thank you,
>>
>> Tom
>>
>>
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Received on Sat Apr 14 2012 - 10:29:16 ART