Abstract: Testing according to this invention allows functions of a first network which is accessible by other networks to be tested without requiring a separate simulator of the other network or interaction with the other networks. This capability is generally accomplished by utilizing a gateway node in the first network to loop-back a query originated in the first network so that it appears as though it originated from another network. The first network then processes the query and originates a reply to the query which is forwarded to the gateway node. Again, the gateway node loops back the reply to the node in the first network which originated the query. Receipt of the loopback reply at the first node provides an indication that the first network can properly respond to queries originated in another network corresponding to the test query.