root@opns:~ # tcpdump -n -nn -i vlan0.18 'icmp6 and not ip6[40] == 128 and not ip6[40] == 129'tcpdump: verbose output suppressed, use -v[v]... for full protocol decodelistening on vlan0.18, link-type EN10MB (Ethernet), snapshot length 262144 bytes20:53:32.931734 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:34.002399 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:35.042986 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:38.957928 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:40.002543 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:41.052590 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:42.259048 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:43.282588 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:44.322688 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:46.333740 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:47.362818 IP6 fe80::1afd:74ff:fec1:2acd > ff02::1:ff65:3a25: ICMP6, neighbor solicitation, who has 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 3220:53:47.362850 IP6 fe80::xxxx:yyyy:zzzz:3a25 > fe80::1afd:74ff:fec1:2acd: ICMP6, neighbor advertisement, tgt is 2a0b:5c81:10:0:xxxx:yyyy:zzzz:3a25, length 32
@Franco : Cried victory too fast. Still the same erratic behaviour. I've turned off IPv6 for now.