Ok, sorry guys my bad...
On previous „versions“ of Banana M1+ I had bittorrent client to download Debian DVD so I don’t need to let notebook running and for some reason the Apple Airport Express keeps passing the „torrent“ questions back to the banana even though it has been reinstalled „from scratch“ and torrent client is not available. I guess that there is something on the router side than on the linux side of the image.
tcpdump:
2016-02-08 11:32:16.038932 IP (tos 0x0, ttl 50, id 48932, offset 0, flags [none], proto UDP (17), length 170)
broadband-188-32-209-120.nationalcablenetworks.ru.49001 > Ankh.51413: [udp sum ok] UDP, length 142
2016-02-08 11:32:16.039033 IP (tos 0xc0, ttl 64, id 20961, offset 0, flags [none], proto ICMP (1), length 198)
Ankh > broadband-188-32-209-120.nationalcablenetworks.ru: ICMP Ankh udp port 51413 unreachable, length 178
IP (tos 0x0, ttl 50, id 48932, offset 0, flags [none], proto UDP (17), length 170)
broadband-188-32-209-120.nationalcablenetworks.ru.49001 > Ankh.51413: [udp sum ok] UDP, length 142
Once again, my bad, sorry :-(