I have a small business client that's moving from one office to another. They're currently using a hosted POP server for mail but we need to move them to an Exchange Server before their move in April. They only have 1 public IP address now for Internet access out and VPN in -- nothing else. It's a small environment with a SnapGear Firewall on a /24 LAN segment. Stupid question time.
Normally, I would assign a dedicated IP address for the Exchange Server but they only have one address now. They will have more available at the new location. But before they do, can I just use the single IP address for their MX record, then create WAN->LAN Forwarding rule for ports 25 and 443 to the new Exchange Server?
They are also wanting to move their web site from a hosted service to a new internal web server -- but we're not planning on doing that until after they move. I suppose even so I could still Forward port 80 on the same single IP address/Firewall to the new internal Web Server, too.
So, if I understand this correctly, is the only real reason to use separate public IP addresses is if you will have the same Port number coming in for multiple purposes with separate servers, like HTTPS? For example, we have an Exchange Server with OWA and a SharePoint Server that both use HTTPS so they would require separate public IP addresses coming into the single Firewall?