Hello After some time i looked again on bug in OSPF that i met before: "Sometimes the link between two routers hangs. Bird reports for example ptp/exstart at one side and ptp/exchange at the other side. Or full/ptp at one side and nothing at the other side." I observed three cases: 1) first node stuck in init/ptp, second node don't even see first node as neighbour. According to tcpdump, first node don't send hello packets. 2) first node (192.168.36.130) stuck in loading/ptp tcpdump: ... 11:54:38.126821 IP 192.168.36.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:38.127048 IP 192.168.36.2 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:39.126493 IP 192.168.36.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:39.128045 IP 192.168.36.2 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:38.127613 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Request (3), length: 36 11:54:38.129563 IP 192.168.36.2 > 192.168.36.130: OSPFv2, LS-Update (4), length: 88 11:54:38.131034 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Ack (5), length: 44 11:54:39.126067 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Request (3), length: 36 11:54:39.129339 IP 192.168.36.2 > 192.168.36.130: OSPFv2, LS-Update (4), length: 88 11:54:39.130246 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Ack (5), length: 44 11:54:40.125492 IP 192.168.36.2 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:40.126112 IP 192.168.36.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:40.126615 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Request (3), length: 36 11:54:40.127747 IP 192.168.36.2 > 192.168.36.130: OSPFv2, LS-Update (4), length: 88 11:54:40.129674 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Ack (5), length: 44 11:54:41.126490 IP 192.168.36.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:41.128826 IP 192.168.36.2 > 224.0.0.5: OSPFv2, Hello (1), length: 48 11:54:41.126068 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Request (3), length: 36 11:54:41.129284 IP 192.168.36.2 > 192.168.36.130: OSPFv2, LS-Update (4), length: 88 11:54:41.130056 IP 192.168.36.130 > 192.168.36.2: OSPFv2, LS-Ack (5), length: 44 ... 3) first node (192.168.36.130) oscillating between loading/ptp and exstart/ptp We can see, that first node also don't send hello packets. tcpdump: 14:24:07.822578 IP 192.168.37.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 14:24:07.823062 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 14:24:07.823588 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 32 14:24:08.824388 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 14:24:08.825092 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 692 14:24:08.825660 IP 192.168.36.130 > 192.168.37.130: OSPFv2, LS-Request (3), length: 60 14:24:08.826215 IP 192.168.37.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 14:24:08.827254 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 692 14:24:08.829550 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 32 14:24:09.822583 IP 192.168.37.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 14:24:09.822828 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 14:24:09.823636 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 32 14:24:10.820982 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 14:24:10.821474 IP 192.168.37.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 14:24:10.821816 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 692 14:24:10.822213 IP 192.168.36.130 > 192.168.37.130: OSPFv2, LS-Request (3), length: 60 14:24:10.823820 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 692 14:24:10.824445 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 32 14:24:11.822592 IP 192.168.37.130 > 224.0.0.5: OSPFv2, Hello (1), length: 48 14:24:11.822836 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 14:24:11.823629 IP 192.168.36.130 > 192.168.37.130: OSPFv2, Database Description (2), length: 32 14:24:12.821025 IP 192.168.37.130 > 192.168.36.130: OSPFv2, Database Description (2), length: 32 I assume that the problem is in timer handling code, which breaks during system time change (for example by agressive NTP daemon). When i manually fiddled with system time, i often triggered the problem. Here are two patches to fix this problem. First patch si probably better but don't work on linux 2.4.x. Second patch should work on it. -- Elen sila lumenn' omentielvo Ondrej 'SanTiago' Zajicek (email: santiago@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."