Development of network applications for commercial purposes often requires extensive verification and validation in large networks. Real networks are however commonly limited in size, number of network devices, and in topology configurations supported. Such limitations make large-scale verification and validation tests hard to accomplish. By emulating a network, the size, router specifications, and topology can be controlled. This allows for more flexible and larger scale testing than in a real network. Also, costs are reduced since no expensive network devices are needed. All in all, there are many advantages with using emulated networks in the development of new network applications. This master's thesis has designed and implemented an MPLS network emulator. The emulator has been used to verify requirements of a network application that captures the topology of an MPLS network.