Because I had so much trouble with this with no help from the router tech support (other than wanting to charge me to "fix" my mac) I am posting this.
I struggled for a couple of days trying to get this to work and the solution was a single check box. As a side benefit, I learned that SIP ALG needed to be disabled to improve the VOIP; it is enabled by default on this router. No more stuttering on the phone lines.
All of the instructions on how to get Mac OSX Server running need to be done beforehand:
port forwarding UDP ports 500, 1701, 4500.
using the external IP address for the "hostname" on the server (dynamic IP through mynetgear.com can be used also).
Finally, even though you have a pass through from the IPV4 firewall to Mac you are using as a server........
IPV6 firewall was still blocking traffic. It can be turned off by checking "Disable IPV6 Firewall Protection"
That's right folks this router has two firewalls. Yipee!
Since Macs recognize IPV6 you get blocked by the IPV6 firewall and the IPV4 firewall. Hopefully this saves someone else two days of there life in the future.
I was lucky enough to have an old bridge modem and a DIR-868L laying around to prove to myself that it was the router and not Comcast service or my Mac.