How to Port Forward Multiple Ports to a Single IP Address via Netgear Genie?

> [...] but received error message [...]

   Something like this one?:

      The specified port(s) are being used by other configurations.
      Please check your configurations of USB Readyshare, Remote
      Management, Port forwarding, Port Triggering, UPnP Port Mapping
      table, RIP, and Internet connection type.

   My favored suspect would be UPnP.  If you're doing this stuff
explicitly, then you don't want the router trying to do it
automatically, behind your back.  I claim.

> [...] stating the IP [address] was already referenced by another
> service [...]

   I doubt that it said that.  There should be no problem with multiple
rules specifying the same server IP address, only multiple rules
specifying the same ports.  On my D7000, for example, I have six rules
pointing at one server (for ports "20-21", "22-23", "25-25", "80-80",
"143-143", and "443-443").  Presumably, I could pack those into fewer
rules, but I prefer to be able to fiddle with them individually.

> Does the router need to be rebooted following each custom service
> addition or would this error message be generated in the event the port
> was actively in use?

   I've never noticed any need for restarts when adding, deleting, or
changing port-forwarding rules, but I have UPnP disabled.  (ADVANCED >
Advanced Setup > UPnP : Turn UPnP On).

   I've always had UPnP disabled, because _I_ want control over incoming
connections to systems on my LAN.  So my experience with it enabled is
nil, so I know nothing about how it interacts with explicit port
forwarding, but I would not be amazed by conflicts between them (as that
message suggests).

   If UPnP is enabled, and a UPnP-eligible server is active, then I'd
expect the router's UPnP stuff to get to work before you could slip an
explicit rule into place.  Knowing nothing, I would not be amazed if you
got flaky behavior from a mix of explicit rules and UPnP.

   Assuming that the router starts fresh every time, and UPnP is the
cause of this behavior, then I'd guess that if you started the router
without that server connected, then you could define all the explicit
rules you wanted, and that might let you leave UPnP enabled along with
the explicit rules.  (Or: disable UPnP, define the explicit rules, and
then re-enable UPnP, if you actually want it.)

   That's my hypothesis, in any case.  (But what do I know?)