BGP AS Path Filter

[dave seddon]

Bgp loop prevention works by never accepting a route with you're own AS in
the path. Therefore if you prepend your route with the AS numbers of the
upstream networks, those networks won't accept the route. However, maybe
your ISP will not accept the route either if the have strict filters (they
probably will accept it), but keep in mind reachability might not work, so
treat carefully.

On Nov 16, 2017 3:44 AM, "Shurshuka" <shurshuka at icloud.com> wrote:

> Hello,
>
> I am newbie in Bird & BGP so pardon my question:
>
> I have server and my own AS/IP's (/24).
> I get default from my provider.
> My provider has a lot of upstreams (different IP transit providers with
> there own AS).
> I want my AS/routes to be announce only from some providers upstreams.
> My provider doesn't provide any self-service BGP communities for that.
> As I understood, I can do this thing with BGP AS Path Filter (Default is
> OK for this? Or Full View required?).
> What filter I need to use (import/export)?
> I tried to use this filter, but it failed:
>
> >         import filter {
> >
> >                 if (bgp_path ~ [= * IP_TRANSIT_PROVIDER_AS_1 PROVIDER_AS
> MY_AS =]) || (bgp_path ~ [= * IP_TRANSIT_PROVIDER_AS_2 PROVIDER_AS MY_AS
> =]) then {
> >
> >                         accept;
> >
> >                 } else reject;
> >         };
>
> Could you please to answer my questions and to tell in what direction to
> move on?
>
> Thanks.
>
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