BGP communities

[Alexander Zubkov]

Have you tried to check that in cli like:
show route where bgp_out(...)
And check that required route has all needed communities:
show route all x.x.x.x/y

On Mon, Apr 6, 2020 at 5:35 PM Fabiano D'Agostino
<fabiano.dagostino96 at gmail.com> wrote:
>
> Hey,
> thank you! I think I am having the same problem they had here:
> https://bird.network.cz/pipermail/bird-users/2010-September/001620.html
>
> But I didn't understand how they solved.
>
> Regards,
> Fabiano
>
> Il giorno lun 6 apr 2020 alle ore 17:16 Cybertinus <bird at cybertinus.nl> ha scritto:
>>
>> Hello Fabiano,
>>
>>
>> BGP Communities are basically tags you add to a prefix that is received from, or send to, a peer. And in Bird you can do whatever you want with these communities. A community by itself has no meaning and has no influence on the routing decision whatsoever. It is the meaning you add to it in your configuration what makes them work.
>>
>> More information about communities: https://en.wikipedia.org/wiki/Border_Gateway_Protocol#Communities
>>
>>
>> Kind regards,
>> Cybertinus
>>
>>
>> On 2020-04-06 17:03, Fabiano D'Agostino wrote:
>>
>> and how these kind of checks are handled?
>> if (myas,peeras) ~ bgp_community  what is bgp_community?
>>
>> Thanks,
>>
>> Il giorno lun 6 apr 2020 alle ore 15:32 Fabiano D'Agostino <fabiano.dagostino96 at gmail.com> ha scritto:
>>
>> Thank you, but "if the route does not come from BGP then false"
>> here I have:
>> protocol pipe a {
>>     table master;
>>     mode transparent;
>>     peer table a;
>>     import all;
>>     export where bgp_out(x); => this becomes false, what does this mean?
>>     #export all;
>> }
>>
>> Thanks,
>>
>> Il giorno lun 6 apr 2020 alle ore 10:50 Bernd Naumann <bena at spreadshirt.net> ha scritto:
>>
>> On 05.04.20 23:08, Fabiano D'Agostino wrote:
>> > Good evening,
>> > could someone explain me the meaning of these lines?
>> >
>> > function bgp_out(int peeras)
>> > {
>> > if ! (source = RTS_BGP ) then return false;
>> > if peeras > 65535 then return true; ### communities do not support AS32
>> > if (0,peeras) ~ bgp_community then return false;
>> > if (myas,peeras) ~ bgp_community then return true;
>> > if (0, myas) ~ bgp_community then return false;
>> > return true;
>> > }
>> >
>> > Thanks,
>> >
>> > Fabiano
>> >
>>
>> Morning,
>>
>> I can not cover the whole section but as a start...
>>
>> * if the route does not come from BGP then false (routing table source?)
>> * if the remote AS Number is greater 65535 (16 Bit) then "just" return
>> true (see AS 32 Bit Numbers, and the non-support of older
>> devices/implementations)
>> * For the next 3 I'm not 100% sure how to read but I found
>> https://bird-users.network.narkive.com/3uDbo6H9/any-ix-willing-to-share-their-config
>>
>> ```
>> 0:XXXXX - Do not announce route to peer XXXXX
>> 0:MyASN - Do not announce route to all peers
>> MyASN:XXXXX - Announce route to peer XXXXX only
>> MyASN:MyASN - Announce routes to all peers. This community is
>> automatically added to all routes that are not
>> tagged with any of MyASN:XXXXX communities.
>> ```
>>
>> Maybe this helps a little bit.
>>
>> Bernd