I've poked around a bit and elements of this question are answered here but I'm still not sure what to do. Here is my situation.
I have a SUSE Linux box that I want to be an Internet-facing SFTP server.
I have Qwest DSL service with a separate MN-700 router that handles DHCP and NAT (i.e. the DHCP is turned off on the Qwest modem/router and an ethernet cable goes to a separate wireless router that dishes out local IP addresses to all devices on my local net, both wired and wireless. One of those devices is the Linux server.)
Qwest apparently blocks many Internet facing ports on DSL modems that get an Internet-facing IP address via DHCP from Qwest. The solution I believe is to get a static IP from Qwest and then port forward port 22 in the DSL modem (and the router?) to the Linux server's local IP address, turning off DHCP on the Linux server and assigning it a static local IP address outside the range that the router uses for DHCP so the port forwarding rule always works. Now as I understand it, connecting to a.b.c.d:22 (where a.b.c.d is the static IP that I buy from Qwest) will forward to 192.168.2.p:22 (where 192.168.2.p is that local IP address of the Linux server) and voila SFTP works.
(a) Does this all seem right - am I missing anything? (b) QWest offers both a single static IP address ($5/month) and a block of 8 IP addresses ($15/month). It seems to me that a single address is all I need. I would need more if I wanted to e.g. run another SFTP server or a web server or something behind the DSL modem, right, but in this case the single static IP will forward to a local static IP and it will just work. Right?
Thanks for help. QWests guidelines on this are not super helpful. They say:
Single static IP's do not provide the ability to assign a gateway address or assign a public IP address to devices on your internal network.
If you lease a single static IP address, it ONLY provides the ability to keep the same public IP assigned to the WAN side of your high-speed Internet modem. If you need to assign a public IP address to devices behind your high-speed Internet modem, you will need to purchase a block of IP addresses.