IPv6 support over IRB interfaces for EVPN

The Ethernet VPN (EVPN ) integrated routing and bridging (IRB) solution supports IPv6 and the Neighborhood Discovery Protocol (NDP). NDP is used by IPv6 nodes on the same link to discover each other's presence, determine each other's Link Layer addresses, find routers, and maintain reachability information about the paths to active neighbors. IPv6 addresses over IRB for EVPN is supported for unique VLAN EVPN instances and for virtual switches with protocol EVPN instances.