Why пахал NAT&Kernel IP Forwarding not working?

гm trying to forward all traffic from tun0 to eth0, below is my интерфейсы:

 eth0      Link encap:Ethernet  HWaddr 12:57:6e:6a:74:85
      inet addr:172.31.32.133  Bcast:172.31.47.255  Mask:255.255.240.0

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-
      inet addr:192.168.77.1  P-t-P:192.168.77.2  Mask:255.255.255.255

The commands I used пахал:

sudo bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i eth0 -o tun0 -m state --state  RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i tun0 -o eth0 -j ACCEPT

I tried in two machines, but all failed, can't get any response from ping.

$ ping -I tun0 8.8.8.8