I presume that you want to get into your server when you are away.
You don't really need bind9 to do this.
Have a look over here : http://en.wikipedia.org/wiki/Dynamic..._for_ISP_users
Chances are your router supports some sort of DDNS already.
There is a free service at : http://www.no-ip.com/services/manage...namic_dns.html
The idea is that your router contacts the DDNS service provider several times a day telling them what IP it is living at. The provider will update its records as to where your server is, and you just use the assigned domain name that you choose when you sign up for the service.
This is a basic setup, with no reverse lookups etc. But it will get you into your server while you are away.