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

Using "area X nssa default-information-originate" will generate Type 7
default. Using "area X nssa no-summary" will generate Type 3 default.
Using both as in "area X nssa no-summary
default-information-originate" will generate both Type 3 and Type 7
default. Receiving routers will have both in the database, but Type 3
will always win and be installed in the routing table.

--
Marko Milivojevic - CCIE #18427 (SP R&S)
Senior CCIE Instructor - IPexpert
On Thu, May 10, 2012 at 2:29 PM, Geert Nijs <Geert.Nijs_at_simac.be> wrote:
> Yes this is true.
>
> No summary = stub area = no redistribution of static or other externals is possible. So to exit the OSPF area , you NEED a default to the ABR. There is no other exit point. Therefore, it is automatically generated in a stub area.
> Nssa = redistribution of external routes is still possible in this case, you might connect a RIP or BGP domain to a NSSA area. You might want to point your default to this bgp or RIP domain. Therefore, cisco
> can't "assume" anymore you want to exit via OSPF ABR. Therefore, the default is not automatically generated in nssa, you must configure it specifically by adding "default-information-originate"
>
> Geert
> CCIE#13792
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of john matijevic
> Sent: zaterdag 14 april 2012 16:29
> To: Marko Milivojevic
> Cc: Tom Kacprzynski; Cisco certification
> Subject: 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 B NSSA, R6 is the ABR and is configured with the following:
>
> B 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
> B  B  110.0.0.0/8 is variably subnetted, 10 subnets, 3 masks
> O IA B  B 110.1.6.1/32 [110/65] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.0.6/32 [110/64] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.4.1/32 [110/129] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.5.1/32 [110/130] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.3.1/32 [110/129] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.1.1/32 [110/130] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 110.1.0.0/24 [110/192] via 110.1.100.6, 00:02:51, Serial0/0
> O IA B  B 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
> B  B  150.100.0.0/24 is subnetted, 2 subnets
> O N2 B  B 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
> B  B  150.100.0.0/24 is subnetted, 2 subnets
> O N2 B  B 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
> B  B  150.100.0.0/24 is subnetted, 2 subnets
> O N2 B  B 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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>>
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