First of all... in your original post you were talking about a private LAN address of 192.168.13.175, but it looks like you are configuring this for a public IP address. If the machine is on a LAN of some sort you need to configure SplitDNS, or have a DNS server on the LAN that can give out internal IP address responses to one set of clients, and the public addresses to external clients (which is how my network is setup).
So again, if this machine is on a LAN everywhere that you have "my.wan.ip" it needs to say 192.168.13.175.
Also your /etc/hosts file needs to have a line like this in it:
Also if it is on a LAN you need to change the /etc/resolv.conf, but i think setting up SplitDNS tells you to do this anyway.
192.168.13.175 xyz.mydomain.com xyz