Recent work has applied Multipath TCP proxies to the prob- lem of bonding a customer’s multiple access interfaces to the Internet, in order to augment available bandwidth, especially in areas with marginal fixed connectivity. However, such proxies only apply to TCP traffic, and while UDP- based media streams can be tunneled through bonded TCP connections, this would lose the advantages of loss-tolerant media-oriented transports. We therefore propose an approach to do interface bonding at layer 3, design a scheduling algorithm to shift traffic between fixed and mobile lines, implemented Linux-based bonding gateways, and tested them within a testbed on Swisscom’s production DSL and LTE networks.