A method for a first vehicle to perform a neighbor discovery in an IP-based vehicular network is disclosed. The method includes, based on the first vehicle failed in a router discovery for a direct registration with an adjacent road-side unit (RSU), sending one or more first neighbor solicitation (NS) messages to a second vehicle; receiving, from the second vehicle, a first neighbor advertisement (NA) message as a response to the first NS message; and sending, to the second vehicle, a second NS message for registering the second vehicle as a relay vehicle based on the first NA message.