Missing route that is shown in filter used by eBGP

[Maria Matejka]

¡Hola!

On Fri, Nov 21, 2025 at 01:37:57PM +0100, Maximilian Wilhelm via Bird-users wrote:
 
> > > - b) filter output vs. export reality
> > >   Independent of whether we filter on "all best" or "all routes", in the
> > >   CLI the filter output shown does include the route - if the filter
> > >   does not match, it also should not print it
> > 
> > Well, if you do `show route filter xyz`, then you get all routes
> > matching that filter. Some protocols pick them. You can do `show route
> > export bgp_to_internet.ipv6` to explicitly re-run the export filter in
> > that context.
> > 
> > I know that it is kinda confusing, and we should probably improve our
> > documentation to show this properly.
> 
> A `show route primary filter xyz` should also be equivalent to what's
> actually exported, right?

Almost! It is, in that case, equivalent to what _should_ be exported
if there was no preexport limitation. The most prominent case is
back-export to Pipe and BGP; these two protocols reject their own
routes, while others (e.g. Babel) accept them.

With that, you need this:

    show route primary filter xyz preexport bgp_to_internet.ipv6

Starting with BIRD 3, some routes might be also export-pending because
BGP runs in different threads than the CLI. This isn't reflected in any
output for now because that information is performance sensitive and
almost impossible to access ad-hoc safely.

We also expect to add protocol contexts, and as soon as this happens,
you would need something like

    show route primary filter xyz preexport bgp_to_internet.ipv6 context { ... }

to match `show route export bgp_to_internet.ipv6` output.

Last but not least, if you change your filters but call `configure soft`,
the affected channels do not reload at all, and therefore to find out
which routes were actually exported, you may ask for

    show route exported bgp_to_internet.ipv6

but if the export filter did any changes, it's already lost because the
export filter is forgotten with the reconfiguration. Only if you have
`export table on`, then you may ask for

    show route export table bgp_to_internet.ipv6

and it actually shows not only what has been exported but also it may
tell you what has been exported but not yet sent to the peer. Not only
that, in BIRD 3, this call works always, and with `export table off`,
it shows exactly the routes which have not yet been sent into the TCP
socket.

And that's been quite an infodump which may have left you even more
confused but now at least it's dumped.

We should definitely do some major updates to the documentation.

Maria

-- 
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
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