ISATAP

ISATAP (intra-site automatic tunnel addressing protocol) is an IPv6 transition mechanism meant to transmit IPv6 packets between dual-stack nodes on top of an IPv4 network. It is defined in the informational RFC 5214.^[1]

Unlike 6over4 (an older similar protocol using IPv4 multicast), ISATAP uses IPv4 as a virtual non-broadcast multiple-access network (NBMA) data link layer, so that it does not require the underlying IPv4 network infrastructure to support multicast.