Cheers, we have reproducible case in the lab where BIRD's OSPF sends LSUPDs with illegal sequence number 0x80000000. Here's what happens: - The OSPF is up and running fine, including BIRD - A change to bird.conf is made that affects OSPF routes - BIRD receives a SIGHUP - Apparently as part of reconfiguration, BIRD floods LSAs with MaxAge and MaxSequenceNumber 0x7fffffff (premature aging -- so far ok) - Immediately after that, but before any other OSPF packet is received (!), BIRD floods the same LSAs again, but with an Age of 2 or 3 (NOT MaxAge) and sequence number 0x80000000 We have a capture file (pcap) of this. If this is any help, I'm happy to e-mail it. The bug here is that sequence number 0x80000000 is reserved and not to be used (RFC 2328, section 12.1.6). As far as I can see, originate_ext_lsa() is called and simply looks up a matching entry in its database (*en). It finds the previously- originated entry with 0x7fffffff, blindly increments it to 0x80000000 (proto/ospf/topology.c:990) and then floods it.