The internal BGP route was successfully exported but could not be imported

[Ondrej Zajicek]

On Wed, Jul 28, 2021 at 08:18:44PM +0800, 智慧雨泽 wrote:
> Hello everyone,I use a pure BGP network to form internal routes (because I
> want to keep the as-path), and the ASN of each router is the same.
> 
> The vserver of LL_IX successfully export the route
> bird> show route for 2602:feda:ab2::/48 export HOME_1_ARCH
> 
> Table master6:
> 2602:feda:ab2::/48   unreachable [BGP_Prefix 11:52:02.569] (200)
>
> But the server at my home could not import it,even i change to import all;
> 
> bird> show route for 2602:feda:ab2::/48 protocol LL_IX
> bird> show route for 2602:feda:ab2:: protocol LL_IX
> bird>
>
> ...
>
> Under what circumstances BGP import will only be "ignored?
> "I think this is the problem.

Hello

Generally, BIRD silently ignores route updates that trigger loop
detection code (either based on bgp_path, and for route reflectors also
based on bgp_cluser_list and bgp_originator_id.

I see that you have 'bgp_path.prepend(LOCAL_ASN)' in your export filter,
that should not be used in IBGP sessions, as that adds local ASN to
bgp_path and triggers loop detection in receiver. Local ASN should be
prepended only when prefix is propagated outside of ASN (on EBGP
session).

Also, it seems that both your sides are route reflectors, that may work
if everything is configured properly (every router uses different cluster
id, which is router id by default), but it is a fringe setup.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."