Link-Local Multicast Name Resolution

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The Link-Local Multicast Name Resolution (LLMNR) is a protocol based on the Domain Name System (DNS) packet format that allows both IPv4 and IPv6 hosts to perform name resolution for hosts on the same local link. It is included in Windows Vista, Windows Server 2008, Windows 7, Windows 8, Windows 10. [1] It is also implemented by systemd-resolved on Linux. [2] LLMNR is defined in RFC 4795 but was not adopted as an IETF standard. [3]

Contents

As of April 2022, Microsoft has begun the process of phasing out both LLMNR and NetBIOS name resolution in favour of mDNS. [4]

Protocol details

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

The responders also listen on TCP port 5355 on the unicast address that the host uses to respond to queries.

Packet header structure

Bit offset0123456789101112131415
0ID
16QROpcodeCTCTZZZZRCODE
32QDCOUNT
48ANCOUNT
64NSCOUNT
80ARCOUNT

See also

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References

  1. LLMNR: The Cable Guy
  2. "systemd 216 available" . Retrieved 2015-08-10.
  3. Mikael Eiman (2015-05-25). "LLMNR, Multicast DNS and names on your LAN" . Retrieved 2021-01-30.
  4. Aligning on mDNS: ramping down NetBIOS name resolution and LLMNR