<div dir="ltr">Just out of curiosity...<br>Is this related to some Kubernetes CNI, or some kind of container underlay that somehow bridges from the underlay to BGP engines within the containers?<br><br>I'm asking this because I've come across similar ideas in the past for deploying PODs that required BGP to fail over to the outside world. For example, Anycasts.</div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">Em sáb., 23 de ago. de 2025 às 12:48, yazan slaila <<a href="mailto:yazan.slaila@hotmail.com">yazan.slaila@hotmail.com</a>> escreveu:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-4790872375274543095">
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Hello there,</div>
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I am currently working on my thesis and experimenting with the BIRD routing daemon. As part of my work, I added a new optional transitive BGP path attribute using the following configuration line:</div>
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The attribute appears correctly in the routing table as follows: (birdc show route all)</div>
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<a href="http://192.168.5.0/24" target="_blank">192.168.5.0/24</a> unicast [router5 15:00:40.321] * (100) [AS5i]</div>
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via 10.0.51.5 on eth2</div>
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Type: BGP univ</div>
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BGP.origin: IGP</div>
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BGP.as_path: 5</div>
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BGP.next_hop: 10.0.51.5</div>
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BGP.local_pref: 100</div>
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<b>BGP.c8 [t]: 20</b></div>
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And this is the way I declare it in my bird.conf file:</div>
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filter export_with_new_attribute {</div>
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new_attribute = hex:20;</div>
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accept;</div>
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}</div>
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But now I would like to use it as part of traffic engineering decisions. Specifically, I would like to understand what steps are required in order to make this new attribute influence the BGP decision-making process for choosing the best path to route the traffic.</div>
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Could you please advise:</div>
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Which files and functions in the BIRD source code are responsible for the BGP path selection process that I need to edit to make my new attribute come after LOCAL_PREF attribute in the priority list? Or if there is a way to do this without the need to edit
the source code.</div>
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Are the previous things correct to add a custom path attribute that is doing something?</div>
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Why is it displaying like this: <b>BGP.c8 [t]: 20? </b>Is there a way to make it appear like this:
<b>BGP.new_attribute [t]: 20?</b></div>
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Is there a standard or recommended way to extend BIRD so that a custom attribute can be incorporated into route preference / best path selection, and if I want to compare 2 values and choose the lowest path that has this value?</div>
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I would greatly appreciate any pointers or guidance that could help me move forward because I did not find any clues on that in your documentation.</div>
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Thank you very much for your time and support.</div>
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Best regards,<br>
Yazan.</div>
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<br>
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</div></blockquote></div><div><br clear="all"></div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr">Douglas Fernando Fischer<br>Engº de Controle e Automação<br><div style="padding:0px;margin-left:0px;margin-top:0px;overflow:hidden;color:black;text-align:left;line-height:130%;font-family:"courier new",monospace"></div></div></div>