ISATAP (intra-site automatic tunnel addressing protocol) is an

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

transition mechanism meant to transmit IPv6 packets between dual-stack nodes on top of an

IPv4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. ...

network. It is defined in the informational RFC 5214. Unlike

6over4 6over4 is an IPv6 transition mechanism meant to transmit IPv6 packets between dual-stack nodes on top of a multicast-enabled IPv4 network. IPv4 is used as a virtual data link layer (''virtual Ethernet'') on which IPv6 can be run. How 6over4 ...

(an older similar protocol using IPv4 multicast), ISATAP uses IPv4 as a virtual non-broadcast multiple-access network (NBMA)

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...

, so that it does not require the underlying IPv4 network infrastructure to support multicast.

Criticisms of ISATAP

ISATAP typically builds its Potential Router List (PRL) by consulting the DNS; hence, in the

OSI model The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems inter ...

it is a lower-layer protocol that relies on a higher layer. 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 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. That is normally done by ensuring that ''proto-41'' (

6in4 6in4, sometimes referred to as SIT, is an IPv6 transition mechanism for migrating from Internet Protocol version 4 (IPv4) to IPv6. It is a tunneling protocol that encapsulates IPv6 packets on specially configured IPv4 links according to the sp ...

) cannot pass through the firewall.

Implementations of ISATAP

ISATAP is implemented in Microsoft

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, Windows Server 2008, Windows Server 2012, Windows Server 2016, Windows Server 2019,

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, and in Cisco IOS (since IOS 12.2(14)S and IOS XE Release 2.1). Due to a patent claim, early in- kernel implementations were withdrawn from both KAME (*

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) and USAGI (Linux). However, the

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IPR disclosure search engine reports that the would-be infringing patent's holder requires no license from implementers. ISATAP support has been supported in Linux since kernel version 2.6.25, the tool isatapd provides a userspace helper. For prior kernels, the open source project Miredo provided an incomplete userland ISATAP implementation, which was removed in version 1.1.6.

References

External links

* {{DEFAULTSORT:Isatap IPv6 transition technologies