I have created the following situation.
When I login to the Forefront TMG machine I CAN ping to 172.30.15.1 (the Internal interface of the Juniper) but when I login to another machine on our DC network (1) I can't ping. I have added the route "route add 172.30.15.0 MASK 255.255.255.0 192.168.100.253" but this does not matter. When I connect my laptop to point (3) (instead of the Forefront TMG) I can also ping the Juniper. So Í think the routing between the internal interface of the forefront and the perimeter interface is not working?