It will not show any ethernet interfaces. A log decoder is designed to be fed log events from event sources, such as Envision, Windows, routers...etc. The devices are configured to either forward events (which is set up from, for example, a router by going into the router and having syslogs forwarded to the log decoder IP) or start up a log collector and having it pull events from Windows boxes. You will not need to run a tap or span port to log decoder.
