[c-nsp] BGP Multihomed Selective/Conditional Advertisement

[Frances Albemuth]

 Seconded.  In fact, this could probably be accomplished merely by
announcing the space once with a bunch of prepends and ensuring the
local preference attribute is greater than other routes Cogent might
see for this space.  174:135, I believe, will raise it to 135, FWIW (5
above their default, IIRC).

 -FC

On Sun, Oct 26, 2008 at 9:08 AM, Nathan <have.an.email at gmail.com> wrote:
> 2008/10/24  <tkacprzynski at spencerstuart.com>:
>>
>> I have been trying to figure out how to do this and maybe someone will be able to help me out.
>>
>> I have two ISP connections ISP ATT and ISP Cogent.
>>
>> (ISP Cogent)    (ISP ATT)
>>     |                       |
>>  RO ------------------- R1
>>
>>
>> ATT would be used for primarily internet and access to our webservers.
>>
>> Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver.
>>
>> I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and the VPN connections on Cogent's network to use ATT.
>>
>> So basically what I was thinking to setup is to accept a default router from ATT and Cogent. Lower the local preference of Cogent and that way I would accomplish using ATT as primary internet access.
>
> I would:
>
> -- forget about conditionals
>
> -- advertise three routes to Cogent. My whole network, with a lot of
> prepends, and the two halves of my network, without prepends but with
> a community saying "don't export".
>
> -- receive from Cogent their networks (the VPN things you want) and
> default. If necessary receive full routes and filter out non-default
> non-Cogent routes. Set local preference lower than default on default
> route from Cogent, and local-preference higher than default on Cogent
> routes.
>
> -- advertise whole network to ATT, without prepends.
>
> -- receive default route from ATT, with default local-preference.
>
> If I've correctly understood what you want then that should do it.
>
> --
> HTH,
> Nathan
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