The Link-Local Multicast Name Resolution (LLMNR) is a protocol based on the

Domain Name System The Domain Name System (DNS) is a hierarchical and distributed name service that provides a naming system for computers, services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various information ...

(DNS) packet format that allows both

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. ...

and

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 ...

hosts to perform name resolution for hosts on the same local link. It is included in

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

Windows Server 2008 Windows Server 2008, codenamed "Longhorn Server" (alternatives: "Windows Vista Server" or "Windows Server Vista"), is the seventh major version of the Windows NT operating system produced by Microsoft to be released under the Windows Server b ...

Windows 7 Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on July 22, 2009, and became generally available on October 22, ...

Windows 8 Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on August 1, 2012, made available for download via Microsoft ...

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. The successor to Windows 8.1, it was Software release cycle#Release to manufacturing (RTM), released to manufacturing on July 15, 2015, and later to retail on July 2 ...

. It is also implemented by

systemd systemd is a software suite that provides an array of system components for Linux operating systems. The main aim is to unify service configuration and behavior across Linux distributions. Its primary component is a "system and service manage ...

-resolved on Linux. LLMNR is defined in RFC 4795 but was not adopted as an IETF standard. As of April 2022, Microsoft has begun the process of phasing out both LLMNR and

NetBIOS NetBIOS () is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, Net ...

name resolution in favour of mDNS.Aligning on mDNS: ramping down NetBIOS name resolution and LLMNR
/ref>

Protocol details

In responding to queries, responders listen on UDP port 5355 on the following link-scope

Multicast address A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link la ...

: * IPv4 - 224.0.0.252,

MAC address A MAC address (short for medium access control address or media access control address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use i ...

01-00-5E-00-00-FC * IPv6 - FF02:0:0:0:0:0:1:3 (this notation can be abbreviated as FF02::1:3), MAC address 33-33-00-01-00-03 The responders also listen on TCP port 5355 on the

unicast Unicast is data transmission from a single sender (red) to a single receiver (green). Other devices on the network (yellow) do not participate in the communication. In computer networking, unicast is a one-to-one transmission from one point in ...

address that the host uses to respond to queries.

Packet header structure

* ID - A 16-bit identifier assigned by the program that generates any kind of query. * QR - Query/Response. * OPCODE - A 4-bit field that specifies the kind of query in this message. This value is set by the originator of a query and copied into the response. This specification defines the behavior of standard queries and responses (opcode value of zero). Future specifications may define the use of other opcodes with LLMNR. * C - Conflict. * TC - TrunCation. * T - Tentative. * Z - Reserved for future use. * RCODE - Response code. * QDCOUNT - An unsigned 16-bit integer specifying the number of entries in the question section. * ANCOUNT - An unsigned 16-bit integer specifying the number of resource records in the answer section. * NSCOUNT - An unsigned 16-bit integer specifying the number of name server resource records in the authority records section. * ARCOUNT - An unsigned 16-bit integer specifying the number of resource records in the additional records section.

References

External links

Link-Local Multicast Name Resolution
Microsoft TechNet * {{IETF RFC, 4795, link=no, Informational, Link-Local Multicast Name Resolution (LLMNR)
LLMNR, Multicast DNS and names on your LAN
Internet protocols Domain Name System Application layer protocols Windows communication and services Windows Server Network protocols

Protocol details

Packet header structure

See also

References

External links