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ĭue to a patent claim, early in- kernel implementations were withdrawn from both KAME (* BSD) and USAGI (Linux). ISATAP is implemented in Microsoft Windows XP, Windows Vista, Windows 7, Windows 8, Windows 10, Windows Server 2008, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows Mobile, Linux, and in Cisco IOS (since IOS 12.2(14)S and IOS XE Release 2.1). That is normally done by ensuring that proto-41 ( 6in4) cannot pass through the firewall. ISATAP carries the same security risks as 6over4: the IPv4 virtual link must be delimited carefully at the network edge, so that external IPv4 hosts cannot pretend to be part of the ISATAP link. A circularity is avoided by relying on an IPv4 DNS server, which does not rely on IPv6 routing being established however, some network specialists claim that these violations lead to insufficient protocol robustness. ISATAP typically builds its PRL by consulting the DNS hence, in the OSI model it is a lower-layer protocol that relies on a higher layer. The local domain is typically obtained via DHCP (over IPv4) or statically configured. In practice, implementations build their PRL by querying the DNS, e.g. Each of these routers is infrequently probed by an ICMPv6 Router Discovery message, to determine which of them are functioning, and to perform unicast-only autoconfiguration (typically, obtain the list of on-link IPv6 prefixes that can be used). Therefore, ISATAP hosts must be configured with a potential routers list (PRL). However, the lack of multicast support prevents the use of automatic Router Discovery. As the link layer address, the IPv4 address, is contained in the lower-order 32-bits of the IPv6 address, Neighbor Discovery is not really needed. That is why ISATAP is a bit more complex than 6over4.įrom the viewpoint of the IPv6 packet, the link layer is the IPv4 packet. Neighbor Discovery īecause ISATAP uses IPv4 as a non multicast/broadcast-capable (unlike Ethernet) link layer, ICMPv6 Neighbor Discovery cannot be done in the usual manner. The link-local address is determined by prepending fe80 ::0200:5efe:… for globally unique addresses, or fe80::0000:5efe:… for private addresses, in front of the 32 bits of the host's IPv4 address.įor example, the global IPv4 address 192.0.2.143 would use fe80::0200:5efe:192.0.2.143 as its link-local IPv6 address. ISATAP defines a method for generating a link-local IPv6 address from an IPv4 address, and a mechanism to perform Neighbor Discovery on top of IPv4.Īny host wishing to participate in ISATAP over a given IPv4 network can set up a virtual IPv6 network interface.