[c-nsp] OSPF LSA Type 3 / 5 question ...

[Fabio Mendes]

If the ABR outer is receiving the /24 from a downstream router on a
different area  and that ABR is also generating a /8 IA to the backbone,
you can just filter out the /24 to other areas via a distribute list.

That way you still have the more specific  /24 on the ABR but the other
routers on area 0 and other areas only see the /8 coming from that ABR.

The /24 will be naturally hidden behind the /8.

I hope it made sense.



On Feb 2, 2017 9:33 PM, "Bryan Holloway" <bryan at shout.net> wrote:

> Fabio,
>
> Thank you for the response! Yes -- that's exactly what I'm trying to do.
> However, the problem is this:
>
> If I use the "summary-address" command, it not only masks it on the rest
> of the backbone, it masks it on the ABR too. Consequently I have to add a
> static route to the downstream router for 10.100.0.0/24.
>
> If I have to add statics on the ABR for every downstream redistributed
> static, it's almost not worth even running OSPF between the two.
>
> What I'm looking for is a way for the static to appear on the ABR, but not
> beyond it. (I.e., mask it everywhere except the ABR.)
>
> Hope that makes sense ... thanks!
>
>                         - bryan
>
>
> On 2/2/17 8:20 PM, Fabio Mendes wrote:
>
>> the full command to summarize external LSA is summary-address, it wasn't
>> very clear on my last email
>>
>> On Thu, Feb 2, 2017 at 9:16 PM, Fabio Mendes <fabio.mendes at bsd.com.br
>> <mailto:fabio.mendes at bsd.com.br>> wrote:
>>
>>     If I understood correctly you are generating an IA LSA via the area
>>     range command on the ABR and are also receiving a E1/2 LSA for a /24
>>     that is part of the IA range and want to mask it behind that same IA
>>     LSA.
>>
>>     One simple way to do it is use the summary command under the ospf
>>     process, announcing a *MailScanner warning: numerical links are
>>     often malicious:* 10.0.0.0/8 <http://10.0.0.0/8> to the backbone
>> area.
>>
>>     Now the backbone has an IA for *MailScanner warning: numerical links
>>     are often malicious:* 10.0.0.0/8 <http://10.0.0.0/8> and a E1/2 for
>>     the same prefix.
>>
>>     In that case the IA will be preferred.
>>
>>     Since the 10.100 subnet is behind the same ABR that's generating the
>>     *MailScanner warning: numerical links are often malicious:*
>>     10.0.0.0/8 <http://10.0.0.0/8> IA into the backbone, you will not
>>     have any connectivity problems by doing that.
>>
>>
>>
>>