IP address specified by ISP

Link Selection and ISP Redundancy ... The VPN tunnel is created using an IP addressof an external interface on the local gateway. ... Security Gateways name and domain name (specified in global properties) - The Security Gateway name is ...
VPNR77 Versions Administration Guide

How to find an ISP for a specific IP address - InfoHQ.com

Configure your network settings to use Google Public DNS

http://www.tldp.org/HOWTO/ISP-Hookup-HOWTO-2.html

How do I specify the Internet connection settings on my ...

If you know that your ISP requires specific servers, select this option. 

Enter the IP address of your ISP's primary DNS server.