On 2/25/25 01:02, Ondrej Zajicek wrote:
On Tue, Feb 25, 2025 at 12:39:29AM +0000, Nigel Kukard via Bird-users wrote:
Hi there,

I'm wondering if someone can point out how the best path is being selected
below in Bird 3.0.1?

In Bird v2 the route via 100.201.0.2 was selected. With the exact same
configuration in Bird v3, the route via 100.201.0.4 is being selected.
Hi

I do not think this is really a change. If two routes have the same
preference and are originated by the same protocol 'class' (e.g. BGP),
they are compared using protocol-specific strategy (e.g. comparing
bgp_local_pref, bgp_path length, ... in case of BGP). But in your case
these two routes are from different protocols 'classes' (bgp_originate4
-> BGP a static4 -> Static), in that case there is only fixed arbitrary
ordering, and that may changed between Bird v2 and v3.

I would suggest that different protocol 'classes' should always use
different preference.
Hi there Ondrej,

Awesome, that explains it perfectly. Thanks!

So just to confirm in this specific case the bgp_local_pref isn't taken into account (ignored) in this specific case, right?

-N





In this case R1 is connected to R2. Both with the same ASN. The below table
is the table I have facing R2.

In terms of my routing tables...
- originate4 =exports to=> bgp4
- static4 =exports to=> master4
- master4 <=exports/imports=> bgp4
- bgp4 <=exports/imports=> t_bgp4_AS65000_r2_peer (below)


1007-Table t_bgp4_AS65000_r2_peer:
  0.0.0.0/0            unicast [bgp_originate4 2025-02-24 23:21:13] * (200)
        via 100.201.0.4 on eth2
  1012- preference: 200
        source: static
        bgp_local_pref: 930
        bgp_large_community: (65000, 3, 1)
  1008- Internal route handling values: 0L 24G 0S id 1
  1007-                     unicast [static4 2025-02-24 23:21:13] (200)
        via 100.201.0.2 on eth2
  1012- preference: 200
        source: static
        bgp_local_pref: 940
        bgp_large_community: (65000, 3, 1) (65000, 5000, 1)
1008- Internal route handling values: 0L 22G 0S id 6


Kind Regards
Nigel

Attachment: OpenPGP_signature.asc
Description: OpenPGP digital signature

Reply via email to