Bird v3 BGP route selection

[Ondrej Zajicek]

On Tue, Feb 25, 2025 at 01:11:16AM +0000, Nigel Kukard wrote:
> 
> 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?

Yes, it is ignored here.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
"To err is human -- to blame it on a computer is even more so."