My config is based on that one... so should be working.
tcpdump on dom0 during pinging 213.186.33.99 on domU
IP (tos 0x0, ttl 113, id 31691, offset 0, flags [none], proto: UDP (17), length: 95) 205.217.228.18.36524 > ns203222.ovh.net.6987: UDP, length 67
11:14:29.629295 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 6, length 64
11:14:29.629454 IP (tos 0x0, ttl 63, id 14885, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 6, length 64
11:14:30.629366 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 7, length 64
11:14:30.629507 IP (tos 0x0, ttl 63, id 14886, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 7, length 64
11:14:31.629434 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 8, length 64
11:14:31.629573 IP (tos 0x0, ttl 63, id 14887, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 8, length 64
11:14:31.629966 IP (tos 0xc0, ttl 64, id 19511, offset 0, flags [none], proto: ICMP (1), length: 112) ns203222.ovh.net > cdns.ovh.net: ICMP host ns203222.ovh.net unreachable, length 92
IP (tos 0x0, ttl 62, id 14885, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 6, length 64
11:14:31.629973 IP (tos 0xc0, ttl 64, id 19512, offset 0, flags [none], proto: ICMP (1), length: 112) ns203222.ovh.net > cdns.ovh.net: ICMP host ns203222.ovh.net unreachable, length 92
IP (tos 0x0, ttl 62, id 14886, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 7, length 64
11:14:31.629977 IP (tos 0xc0, ttl 64, id 19513, offset 0, flags [none], proto: ICMP (1), length: 112) ns203222.ovh.net > cdns.ovh.net: ICMP host ns203222.ovh.net unreachable, length 92
IP (tos 0x0, ttl 62, id 14887, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 8, length 64
11:14:32.430974 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 91.121.178.250 > ns203222.ovh.net: ICMP echo request, id 12107, seq 48642, length 64
11:14:32.430998 IP (tos 0x0, ttl 64, id 13052, offset 0, flags [none], proto: ICMP (1), length: 84) ns203222.ovh.net > 91.121.178.250: ICMP echo reply, id 12107, seq 48642, length 64
11:14:32.629501 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 9, length 64
11:14:32.629637 IP (tos 0x0, ttl 63, id 14888, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 9, length 64
11:14:33.629573 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 10, length 64
11:14:33.629710 IP (tos 0x0, ttl 63, id 14889, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 10, length 64
11:14:33.982499 IP (tos 0xc0, ttl 64, id 32800, offset 0, flags [none], proto: ICMP (1), length: 123) ns203222.ovh.net > 71.238.25.166: ICMP ns203222.ovh.net udp port 57211 unreachable, length 103
IP (tos 0x0, ttl 117, id 56210, offset 0, flags [none], proto: UDP (17), length: 95) 71.238.25.166.10950 > ns203222.ovh.net.57211: UDP, length 67
11:14:34.629753 IP (tos 0x0, ttl 63, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) ns203222.ovh.net > cdns.ovh.net: ICMP echo request, id 57, seq 11, length 64
11:14:34.629867 IP (tos 0x0, ttl 63, id 14890, offset 0, flags [none], proto: ICMP (1), length: 84) cdns.ovh.net > ns203222.ovh.net: ICMP echo reply, id 57, seq 11, length