It was a little bit strange situation, I found my outer interface in a PROMISC mode.
“ip a” or “ifconfig” output shows that my eth0 interface was in the PROMISC mode, but I don’t understand, why?
eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 ...
I don’t used tcpdump or similar tools in this moment.
After I spend some time to my favorite search engine, I found how to disable manually this mode:
ifconfig eth0 -promisc