The full form of RREQ is Route Request. It’s used on Computing ,Networking in Worldwide

When one node needs to send a message to another node for which it does not already have a route it broadcasts a Route Request (RREQ) message. By sending RREQ the node is asking the network how to get to the destination. When RREQ message arrives at its destination, a “Route Reply” (RREP) message will immediately get passed back to the origin, indicating that a route to the destination was found. The RREQ message contains several key bits of information like the source, the destination, the lifespan of the message, broadcast ID etc.