What sets the ZyWALL 10 apart from most other routers that I've
tested is its five different NAT modes (Multi-NAT). (Check
ZyXEL FAQ for more details.)
These new NAT modes will be useful primarily to people who
have multiple IP addresses from their ISP.
NOTE: The '10 has only one physical WAN port,
so it can't be connected to multiple WAN feeds, i.e.
both a cable modem and a DSL connection. Your multiple
WAN IP addresses must come from the same ISP.
With Multi-NAT, for example, you can have more than one of the
same type server (HTTP for example) running on the same port number,
but on different IP addresses (or domains). This is like
having multiple "DMZ" capability, but you still get
the firewall protection for the servers.
The old "SUA" (Single User Account) NAT mode is still
supported, and it fortunately has its own page in the product's
Web admin interface.
So you can easily allow servers on your LAN can be accessed from the
Internet, but you are limited to 12 single-port-number-to-LAN
IP mappings. You can't specify TCP or UDP protocol, and you can't
map port ranges, either. One of the twelve mappings
is dedicated to the Default Server mapping. This
is similar to the DMZ Host, or Exposed Computer feature
on other routers. Another mapping is dedicated to Port 1026 "RR
Reserved", so this leaves 10 single port mappings that you
can actually use.