Iptables forward all traffic to a specified port, to another device

Solution 1:

This rule will forward 80 port to 192.168.42.10

iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 192.168.42.10:80

but this is not enough If you want to get back traffic then you should add this rule

iptables -t nat -A POSTROUTING -p tcp -d 192.168.42.10 --dport 80 -j SNAT --to-source 192.168.42.1

where ip address 192.168.42.1 is your iptables computer

These two rules have to solve the task.