There are 4 ways you can publish your server to the internet from your house:

1. Using the modem provided by your ISP, configure the DMZ feature to host all services from your server.

2. Using the modem provided by your ISP, configure the port forwarding feature to host specific port from your server such as TCP port 80 for Web service...

3. Turning the modem provided by your ISP to a normal layer-2 switch by enabling its BRIDGE mode in the configuration page.

4. Asking your Internet Service Provider allow the IP passthrough feature to get additional public IP addresses.

You should ask your Internet Service Provider for a free second IP passthrough

You would like to set up a network related lab in your house but you do NOT like to mess up your home network. So the only way you can do it is asking your ISP for a free second IP address.