Reducing network laboratory costs: demonstrating connectivity with ping reflectors

A major problem faced in constructing a teaching laboratory for data networking is the cost of the equipment. Multiple pieces of equipment are often needed to do little more than demonstrate connectivity. This paper describes approaches to configuring computers in a TCP/IP network that meet this need at a lower cost. Particular emphasis is placed on techniques that can be used with remote access laboratories. In addition to a novel technique described in detail, several well-known or obvious approaches are described for purposes of comparison. The approach described in greatest detail simulates multiple interfaces with a single interface by assigning multiple IP addresses to that interface. IP filters are then used to alter the behavior of the interface so that it closely resembles the behavior seen with wiring changes. With this approach, no actual wiring will be changed. This allows some assignments to be done remotely, which would be impractical otherwise, opens the laboratory for use in off-hours, and makes distance education possible