A method and system for preventing loops in a network including network devices operating different protocols for providing loop-free topology are disclosed. In one embodiment, a method includes receiving link state information at a network device operating a first protocol and in communication with a network device operating a second protocol, creating at least one tunnel to one or more other network devices operating the first protocol and in communication with a network device operating the second protocol, receiving a proposal, blocking designated boundary ports in communication with network devices operating the second protocol, and transmitting an agreement.