Par rapport à ton premier message, j'ai fait un tcpdum si ça peu aider, en configuration avec le openwrt branché sur la Bbox TV:
root@OpenWrt:/etc/config# tcpdump -i eth1.100 icmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1.100, link-type EN10MB (Ethernet), capture size 262144 bytes
00:37:17.874258 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:17.979244 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64
00:37:18.509410 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > nsabo2.bouyguesbox.fr: ICMP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr udp port 33054 unreachable, length 320
00:37:24.034159 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:24.139290 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64
00:37:30.195758 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:30.300388 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64
00:37:36.353936 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:36.458659 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64
00:37:40.556177 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > nsabo2.bouyguesbox.fr: ICMP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr udp port 61860 unreachable, length 276
00:37:42.513967 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:42.619022 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64
00:37:48.673854 IP i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr > public1.114dns.com: ICMP echo request, id 34818, seq 0, length 64
00:37:48.778596 IP public1.114dns.com > i15-les02-ntr-176-181-167-132.sfr.lns.abo.bbox.fr: ICMP echo reply, id 34818, seq 0, length 64