A routing platform for routing 4G and 5G mobile data traffic in a mobile core networks implementing Option-3 of 5G Non-Standalone deployment. The routing platform captures S6a Diameter messages sent between a Mobility Management Entity (MME) and a Home Subscriber Server (HSS) and examines the captured messages to determine whether a user equipment (UE) is configured for a 5G data connection. The routing platform intercepts a GTP Create-Session-Request message sent from a Serving Gateway (SGW) and determines whether the GTP message is associated with the UE previously determined to be configured for a 5G data connection. If the GTP message is associated with the UE configured for a 5G data connection, the GTP message is either sent to a dedicated 5G Packet Network Data Gateway (PGW) or the GTP message is modified so that a single PGW handling both 4G and 5G traffic can establish a 5G session for the UE.