BGP communities

[Cybertinus]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://trubka.network.cz/pipermail/bird-users/attachments/20200406/6ac66fb4/attachment.htm>