DNS, Website, External IP, Internal IP setup?

[webking]

hi all,

please show me to how to set this up.

I have a cable modem external internet IP: 69.120.120.120 (example)
Internal ISPConfig ip: 192.168.15.101 (this my the machine)
A domain: abc.com

I have setup NS at godaddy: ns1.abc.com => 69.120.120.120 and ns2.abc.com => 69.120.120.111

when I ping ns1.abc.com i get results using dig command but when ping using dig ns abc.com i get :

;; global options: printcmd
;; connection timed out; no servers could be reached

What are the steps to setup correctly using a home computer on a router with an Internet IP and using a domain?

I can access ISPCon via external IP and Internal IP as well. My problem now is how to host a domain using this home server. Thanks