BIRD 1.3.9 running on FreeBSD 9.1 with next interfaces (not all showed): em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MAGIC,VLAN_HWTSO> ether 68:05:ca:0e:d3:e1 inet 10.254.0.2 netmask 0xffff0000 broadcast 10.254.255.255 vlan1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=3<RXCSUM,TXCSUM> ether 50:46:5d:b1:98:6c inet 10.90.90.91 netmask 0xfffffff8 broadcast 10.90.90.95 inet6 2a03:e2c0::1 prefixlen 64 nd6 options=1<PERFORMNUD> media: Ethernet autoselect (1000baseT <full-duplex>) status: active vlan: 1 parent interface: re0 ospf configuration: protocol ospf { area 0 { interface "em0" ; }; } Bird send HELLO packet with wrong mask (and Designated Router also): tcpdump: listening on em0, link-type EN10MB (Ethernet), capture size 65535 bytes 20:04:06.186362 IP (tos 0xc0, ttl 1, id 29198, offset 0, flags [none], proto OSPF (89), length 64) 10.254.0.2 > 224.0.0.5: OSPFv2, Hello, length 44 Router-ID 185.17.0.1, Backbone Area, Authentication Type: none (0) Options [External] Hello Timer 10s, Dead Timer 40s, Mask 255.255.255.240, Priority 1 Designated Router 10.90.90.1