If a server is placed under NAT how does incoming requests are mapped to the servers private adddress?

Question

There is no problem if a client is placed under NAT. I know How it is handled.

Answer 1

LIke Colin says, check the router and the port forwarding.

You need to forward ALL ports that are needed by your server.
Port 21 is FTP, 25 is SMTP, port 53 DNS, port 80 Web server, port 110 POP, port 443 is SSL if you are running SQL etc you need to forward those also.

Answer 2

On real routers (not firewalls), when you set a NAT, all traffic is forwarded inside to the NATed address, we then control outside access with access-control-lists saying which ports are allowed.

PAT is the process of port forwarding. We use PAT when we have only one Global IP address and many inside hosts.

A NAT is by default a 1 to 1 translation. When we use multiple inside hosts on one outside, global IP address, then we use PAT. This is where we "overload" the one outside global IP address and map to many inside hosts via source ports.

NAT and PAT are not the same thing but the acronym NAT is frequently used when discussing PAT.

Hope I didn't muddy the issue. =)

Answer 3

On the router you need to set port forwarding for any ports you need on the server, this means you need to set the server ip address manually. Only open the essential port.