Iptables is a firewall, installed by default on all official Ubuntu distributions (Ubuntu, Kubuntu, Xubuntu). When you install Ubuntu, iptables is there, but it allows all traffic by default. [1][1]

Show NAT

$ sudo iptables -t nat -v -L -n --line-number
...
Chain PREROUTING (policy ACCEPT 1465K packets, 97M bytes)
num   pkts bytes target     prot opt in     out     source               destination         
1      192  9920 DNAT       tcp  --  *      *       0.0.0.0/0            192.168.1.1         tcp dpt:8077 to:10.10.10.10:8000
2     947K   49M DNAT       tcp  --  *      *       0.0.0.0/0            192.168.1.1         tcp dpt:8078 to:10.10.10.11:80
3     2168  128K DNAT       tcp  --  *      *       0.0.0.0/0            192.168.1.1         tcp dpt:8075 to:10.10.10.12:8000

Delete PREROUTING NAT

sudo iptables -t nat -D PREROUTING 3 # 3 is Chain num

Create PREROUTING NAT

NAT 192.168.1.1:8071 to container 10.10.10.19:8069

sudo iptables -t nat -A PREROUTING -d 192.168.1.1 -p tcp --dport 8071 -j DNAT --to-destination 10.10.10.19:8069

Save iptable

Executing the following commands as root

iptables-save > /etc/iptables/rules.v4