A Mobile Ad hoc NETwork (MANET) could establish a communication in network infrastructure-less places. In an ad hoc network, a basic IPv6 address auto-configuration mechanism has an address allocation problem. A number of address allocation mechanisms have been suggested. However, mobile node(MN)s have high mobility and random address. Therefore, they do not guarantee fixed and shared network prefix. To guarantee equality of network prefix among connected MNs, we propose a MANET identifier (MANET ID). This scheme allows MNs to share the same MANET ID using a creation & negotiation phase. By sharing an equal MANET ID, we achieve a number of enhancements for existing ad hoc network technologies: Enhanced group communication, avoiding duplicate address detection storms, and enhanced zone routing protocol (ZRP).