<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body style='font-size: 10pt; font-family: Verdana,Geneva,sans-serif'>
<p>Hello Fabiano,</p>
<p><br /></p>
<p>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.</p>
<p>More information about communities: <a href="https://en.wikipedia.org/wiki/Border_Gateway_Protocol#Communities">https://en.wikipedia.org/wiki/Border_Gateway_Protocol#Communities</a></p>
<p><br /></p>
<div id="signature">
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Kind regards,<br />Cybertinus</div>
</div>
<p><br /></p>
<p id="reply-intro">On 2020-04-06 17:03, Fabiano D'Agostino wrote:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div id="replybody1">
<div dir="ltr">and how these kind of checks are handled?
<div><span style="color: #161616; font-family: 'PT Sans',HelveticaNeue,'Helvetica Neue',Helvetica,Arial,sans-serif; font-size: 14px;">if (myas,peeras) ~ bgp_community</span> <span style="color: #0000ff;">what is bgp_community?</span></div>
<div><span style="color: #0000ff;"> </span></div>
<div><span style="color: #000000;"><span style="background-color: #f3f3f3;">Thanks, </span></span></div>
</div>
<br />
<div class="v1gmail_quote">
<div class="v1gmail_attr" dir="ltr">Il giorno lun 6 apr 2020 alle ore 15:32 Fabiano D'Agostino <<a href="mailto:fabiano.dagostino96@gmail.com" rel="noreferrer">fabiano.dagostino96@gmail.com</a>> ha scritto:</div>
<blockquote class="v1gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left: 1px solid #cccccc; padding-left: 1ex;">
<div dir="ltr">Thank you, but "if the route does not come from BGP then false"
<div>here I have:</div>
<div>protocol pipe a {<br /> table master;<br /> mode transparent;<br /> peer table a;<br /> import all; <br /> export where bgp_out(x); => <span style="color: #0000ff;">this becomes false, what does this mean?</span><br /> #export all;<br />}</div>
<div> </div>
<div>Thanks,</div>
</div>
<br />
<div class="v1gmail_quote">
<div class="v1gmail_attr" dir="ltr">Il giorno lun 6 apr 2020 alle ore 10:50 Bernd Naumann <<a href="mailto:bena@spreadshirt.net" rel="noreferrer">bena@spreadshirt.net</a>> ha scritto:</div>
<blockquote class="v1gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left: 1px solid #cccccc; padding-left: 1ex;">On 05.04.20 23:08, Fabiano D'Agostino wrote:<br />> Good evening,<br />> could someone explain me the meaning of these lines?<br />> <br />> function bgp_out(int peeras)<br />> {<br />> if ! (source = RTS_BGP ) then return false;<br />> if peeras > 65535 then return true; ### communities do not support AS32<br />> if (0,peeras) ~ bgp_community then return false;<br />> if (myas,peeras) ~ bgp_community then return true;<br />> if (0, myas) ~ bgp_community then return false;<br />> return true;<br />> }<br />> <br />> Thanks,<br />> <br />> Fabiano<br />> <br /><br />Morning,<br /><br />I can not cover the whole section but as a start...<br /><br />* if the route does not come from BGP then false (routing table source?)<br />* if the remote AS Number is greater 65535 (16 Bit) then "just" return <br />true (see AS 32 Bit Numbers, and the non-support of older <br />devices/implementations)<br />* For the next 3 I'm not 100% sure how to read but I found <br /><a href="https://bird-users.network.narkive.com/3uDbo6H9/any-ix-willing-to-share-their-config" target="_blank" rel="noopener noreferrer">https://bird-users.network.narkive.com/3uDbo6H9/any-ix-willing-to-share-their-config</a><br /><br />```<br />0:XXXXX - Do not announce route to peer XXXXX<br />0:MyASN - Do not announce route to all peers<br />MyASN:XXXXX - Announce route to peer XXXXX only<br />MyASN:MyASN - Announce routes to all peers. This community is<br />automatically added to all routes that are not<br />tagged with any of MyASN:XXXXX communities.<br />```<br /><br />Maybe this helps a little bit.<br /><br />Bernd</blockquote>
</div>
</blockquote>
</div>
</div>
</blockquote>
</body></html>