How to Set Up Cross‑Network Port Mapping on Windows and Linux

1. Windows Port Mapping

1. Query existing mappings

netsh interface portproxy show v4tov4

2. Query mappings for a specific IP

netsh interface portproxy show v4tov4 | find "[IP]"

3. Add a new mapping

netsh interface portproxy add v4tov4 listenaddress=[ExternalIP] listenport=[ExternalPort] connectaddress=[InternalIP] connectport=[InternalPort]

4. Delete a mapping

netsh interface portproxy delete v4tov4 listenaddress=[ExternalIP] listenport=[ExternalPort]

2. Linux Port Mapping

1. Enable packet forwarding

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -j MASQUERADE
iptables -A FORWARD -i [InternalInterface] -j ACCEPT
iptables -t nat -A POSTROUTING -s [InternalSubnet] -o [ExternalInterface] -j MASQUERADE

2. Set up a port forwarding rule

iptables -t nat -A PREROUTING -p tcp --dport [ExternalPort] -j DNAT --to-destination [InternalIP]:[InternalPort]

3. Example topology

4. Configure temporary mapping on Server4 (Linux)

# Enable forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -j MASQUERADE
iptables -A FORWARD -i ens33 -j ACCEPT
iptables -t nat -A POSTROUTING -s 192.168.50.0/24 -o ens37 -j MASQUERADE
# Port mappings
iptables -t nat -A PREROUTING -p tcp --dport 8081 -j DNAT --to-destination 192.168.50.11:8080
iptables -t nat -A PREROUTING -p tcp --dport 8082 -j DNAT --to-destination 192.168.50.12:8080

5. Permanent configuration (Linux)

Append the same commands to /etc/rc.local to make them survive reboots.

6. Verify the mappings

curl http://172.16.2.100:8081/index.html
curl http://172.16.2.100:8082/index.html

3. Windows Equivalent Commands

Replace the Linux iptables commands with the corresponding netsh interface portproxy commands shown in section 1.

4. Sample Windows network settings

Two NICs: Ethernet0 – 192.168.50.105/24 (internal), Ethernet1 – 172.16.2.105/24 (external).

5. Windows permanent mapping example

netsh interface portproxy add v4tov4 listenaddress=172.16.2.105 listenport=8081 connectaddress=192.168.50.11 connectport=8080
netsh interface portproxy add v4tov4 listenaddress=172.16.2.105 listenport=8082 connectaddress=192.168.50.12 connectport=8080
netsh interface portproxy show v4tov4

6. Test from a client machine

curl http://172.16.2.105:8081/index.html
curl http://172.16.2.105:8082/index.html
curl http://172.16.2.11:8080/index.html

Successful responses confirm that the external client can reach services hosted on the internal network through the configured port mappings.