[44net] testing for source address filtering....

Occasionally I have access to 2 Verizon DSL connections in the same location. the connections while being the same provider are generally a dynamic IP from different /24 subnets and there's about 4 hops between them. (once they reach a common point a couple hops away all other traceroute data is the same. how can I test to see if one connection filters source addresses belonging to the other? (and any guesses as to what the results may be?) Eric