TeamViewer can make use of DynGate (Firewall Router). Together with DynGate
TeamViewer can communicate across firefall barriers and proxys without any need for special firewall configurations. DynGate works with static and dynamic IP-Adresses. DynGate integrates so smart in TeamViewer that you'll forget they are two
products. While TeamViewer is a free solution, DynGate is a commercial product.