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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>
<pre><div style="direction: ltr; text-align: left; text-indent: 0px; white-space: pre-wrap; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><code>attribute bgp 200 bytestring new_attribute;
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The attribute appears correctly in the routing table as follows: (birdc show route all)</div>
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192.168.5.0/24 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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<br>
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And this is the way I declare it in my bird.conf file:</div>
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<br>
</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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