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

Hmm, not sure if this applies here, but I run into something not so long
ago:
An nssa area was used to connect some ABRs with some internal routers,
and all ABRs (3) where configured with "area 1 nssa no-summary
no-redistribution". This was running fine until we had a partition
of the network and discovered that one of the ABRs, which was running a
newer code, was not injecting a default with that configuration.
(none, no type 7, no type 3). I had to add an explicit
"default-information-originate" to get a type 7 default.

HTH.
-Carlos

Marko Milivojevic @ 10/05/2012 18:45 -0300 dixit:
> 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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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net