Source address conversion (intranet access to extranet)
When sending IP packets, convert the address of the internal network (source address) to the Eth1 address of the external network (12.34.56.78)
eth1 is the network card (export)
and then delete the first rule : (or change the above -A For -I)
iptables -t nat -D POSTROUTING 1
Target address conversion (extranet access to intranet)
When sending IP packets, convert the address of the external network (destination address) to the host address of the internal network (192.168.1.1) and
add the conversion rule.
Add the PREROUTING rule.
Add the FORWORD rule:
iptables -F PREROUTING