Log con debug 6:
...
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.378755] about to send v6 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.378924] nat46_ipv4_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.379060] nat46_ipv4_input protocol: 6, len: 40, flags: 01
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.379271] [nat46] pairs_xlate_v4_to_v6_outer result: src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.379502] about to send v6 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.379670] nat46_ipv4_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.379807] nat46_ipv4_input protocol: 6, len: 40, flags: 01
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.380018] [nat46] pairs_xlate_v4_to_v6_outer result: src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.380248] about to send v6 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.381405] nat46_ipv6_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.381542] nat46_ipv6_input next hdr: 6, len: 60, is_fragment: 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.381768] [nat46] pairs_xlate_v6_to_v4_outer result src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.381995] about to send v4 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.382163] nat46_ipv6_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.382301] nat46_ipv6_input next hdr: 6, len: 91, is_fragment: 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.382527] [nat46] pairs_xlate_v6_to_v4_outer result src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.382753] about to send v4 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.382922] nat46_ipv6_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.383059] nat46_ipv6_input next hdr: 6, len: 91, is_fragment: 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.383285] [nat46] pairs_xlate_v6_to_v4_outer result src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.383512] about to send v4 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.383679] nat46_ipv6_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.383814] nat46_ipv6_input next hdr: 6, len: 60, is_fragment: 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.384040] [nat46] pairs_xlate_v6_to_v4_outer result src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.384266] about to send v4 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.384441] nat46_ipv4_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.384578] nat46_ipv4_input protocol: 6, len: 40, flags: 01
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.384789] [nat46] pairs_xlate_v4_to_v6_outer result: src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.385020] about to send v6 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.385187] nat46_ipv6_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.385321] nat46_ipv6_input next hdr: 6, len: 60, is_fragment: 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.385546] [nat46] pairs_xlate_v6_to_v4_outer result src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.385772] about to send v4 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.386153] nat46_ipv4_input packet
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.386290] nat46_ipv4_input protocol: 6, len: 40, flags: 01
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.386501] [nat46] pairs_xlate_v4_to_v6_outer result: src 0 dst 0
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.386731] about to send v6 packet, flags: 00
Mon Dec 13 12:50:57 2021 kern.warn kernel: [43670.397577] nat46_ipv6_input packet
...