The TMG firewall has some built in logic to test the availability of the ISP links it uses to connect to the Internet. If you want to learn more about that subject, check out Tom’s article over at http://www.isaserver.org/tutorials/Kicking-Tires-TMG-2010-RC-ISP-Redundancy-Part1.html
However, if you’d like to customize the intervals used for link testing, you’ll be sad that there is no option in the TMG firewall console that enables you to do this. How about a simple set of Registry settings? Nope. You’ll not find any of those either.
However, if you want to script the changes (sure, why not – isn’t that why I decided to use TMG instead of Cisco?), then the TMG Firewall Team has some advice for you over at:
DEBRA LITTLEJOHN SHINDER
MVP (Enterprise Security)