Dynamical DNS: 2 IPs, 4 machines, 1 Masterzzzzz!

[kha0s]

Here's the deal folks:
I've got two places, separated by a big Ocean, with ADSL connections. Let's call them "Home" and "Jail". I've got 2 computers at Home and 2 computer at Jail. On each computer, (all Gentoo powered naturally) there are at least 2 users (root and joe).

Objective: control them all by "ssh" from anywhere in the earth (and even from the Moon if they ever get broadband up there)

1: Getting a static IP for Home and Jail:
I've intersected from several sources that DynDNS.com is the place to go. I've checked it out and it seems they offer 5 free hostnames per registration:
Question1: Does that mean per registration I get: one static ip for Home, one static ip for Jail, and end up with 3 spare ones?

2: Getting past my NAT-FIREWALL router
On Home, I've got a DG834N and on Jail I've got a DG834PN. The first one even has embedded support for DynDNS.com! The point is they're both have a NAT firewall. Now here comes the BIG issue:
In both routers, I can add a "Inbound Service" firewall rule that takes the following arguments:

[cipherus]

With a service like DynDNS, they do not give you a static IP address. You sign up for a domain named (for example jail.dyndns.com) and when your IP address changes, it will update with their service automatically. Well not exactly automatically, some routers contain a service that will update to dyndns whenever you IP address changes. If your router does not have this, then you will need to run a service from one of your computers which does this. The only way to really figure it out is to just sign up and start testing, it is afterall a completely free service.

Secondly, with your router and port forwarding, you can only have port 22 (the ssh port) forwarded to one computer on your LAN. The trick is, you can forward a different port (maybe port 27) to a different computer. Some routers let you define which external port gets mapped to which internal port, for example, making jail.dyndns.com port 27 forward to internal LAN ip address 192.168.0.105 port 22. However, if your router doesn't have this functionality, then you will have to change your sshd to listen on port 27 instead of 22. For further reading on how to change your sshd listening port do this command:

[kha0s]

I see... Fortunately I'm not expecting to handle more than 65535 machines under the same sub-net, . What I haven't figured out yet is if DynDNS.com allows you to created 5 different domain names for 5 different IP addresses, i.e, if with only one registration, keeping the example above, I would be able to have a domain name for House's IP and a domain name for Jail's IP. I would very much like to exclude the possibility that what they're really saying is that you get 5 different names for the SAME IP, with each registration....

PS: Yes, I noticed! The question is, was the door opened or was the door LEFT opened....
_________________
Who will guard the guards?

[cipherus]

it was right opened. and for the record, there is no spoon.