Hi, I use bird 2.0.7 on FreeBSD 12.1 for 3 routers with bgp and ospf/ospf v3. This is my weathermap : https://librenms.securmail.fr/weathermap/ (to help for understand my network architecture) I have a configuration for my internal subnet : protocol ospf ospf_ipv4_internal { ipv4 { import keep filtered; import limit 200 action block; import filter { if (net ~ [ 10.0.0.0/8+, 172.16.0.0/12+, 192.168.0.0/16+ ]) then { accept; } else { reject; } }; export none; }; area 0.0.0.0 { interface "tap0"; }; }; The same for IPv6 : protocol ospf v3 ospf_ipv6_internal { ipv6 { import all; import keep filtered; import limit 200 action block; import filter { if (net ~ [ ::/0 ]) then { reject; } if (net ~ [ fd00:208::/32+ ]) then accept; }; export none; }; area 0.0.0.0 { interface "tap0"; }; }; But, sometimes, ospf_ipv4_internal on 2 routers (always the same) lost routes learn by this ospf configuration. On the router who has the routes (on iFog router) : bird> show route all protocol ospf_ipv4_internal Table master4: 192.168.0.0/24 unicast [ospf_ipv4_internal 06:16:20.781] E2 (150/10/64) [172.16.56.3] via 172.16.56.3 on tap0 Type: OSPF-E2 univ OSPF.metric1: 10 OSPF.metric2: 64 OSPF.tag: 0x00000000 OSPF.router_id: 172.16.56.3 172.16.55.0/24 unicast [ospf_ipv4_internal 06:16:14.779] I (150/20) [172.16.55.7] via 172.16.56.2 on tap0 Type: OSPF univ OSPF.metric1: 20 OSPF.router_id: 172.16.55.7 172.16.56.0/24 unicast [ospf_ipv4_internal 06:01:36.079] I (150/10) [193.148.249.128] dev tap0 Type: OSPF univ OSPF.metric1: 10 OSPF.router_id: 193.148.249.128 On the router who lost them (on Scipio router) : bird> show route all protocol ospf_ipv4_internal Table master4: 172.16.56.0/24 unicast [ospf_ipv4_internal 09:33:17.530] I (150/10) [89.234.186.30] dev tap0 Type: OSPF univ OSPF.metric1: 10 OSPF.router_id: 89.234.186.30 On this router, in the log file i have this error : 2020-08-27 09:50:12.349 <ERR> ospf_ipv4_internal: Socket error on tap0: Invalid argument The configuration is the same between all routers. I missed something but i don't understand what ^^ Can you help me on this? Thanks