OK, the problem seems to have been the name of the filter. BIRD says "syntax error, unexpected DEFAULT" so I renamed the filter to "reject_default" and that works. What did BIRD not like about "default-reject"? Also, I have said filter configured as import and export filters in both ospfv3 and kernel6 but the router in question still announces the default route via OSPFv3. Can anybody tell me what filter I have to use in which direction on which protocol so that a) the router ignores the incoming OSPF default route and b) does not redistribute his default route via OSPF? Mit freundlichen Grüßen, Marcus Büttemeyer ---------- Forwarded message --------- From: Marcus Büttemeyer <marcus.buettemeyer@gmail.com> Date: Sun, 7 Aug 2022 at 15:12 Subject: Filter OSPF to kernel routes To: <bird-users@network.cz> Hello, I'm distributing my default route via OSPFv3 from my edge router. For testing purposes I would like to ignore that default route on one of my routers. Said router gets a default route via IPv6 router advertisements but the OSPF route is preferred. So I tried: filter default-reject { if ::/0 ~ net then reject; } [...] protocol ospf v3 ospfv3 { ipv6 { import filter default-reject; [...] and protocol kernel kernel6 { ipv6 { export filter default-reject; }; [...] The filter seems to be correct, "show route filter ..." works in birdc. But I still have the OSPF default route. So it seems I misunderstand filters in BIRD completely. Can anybody point me in the right direction? Thanks in advance, Marcus Büttemeyer