networking layer2 ai_generated true

NDP: Duplicate Address Detection failed for fe80::1 on eth0, address already in use by 00:1a:2b:3c:4d:5e

ID: networking/ipv6-ndp-duplicate-address

Also available as: JSON · Markdown · 中文
79%Fix Rate
86%Confidence
1Evidence
2024-03-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Linux kernel 6.2.0 active — — —
FreeBSD 13.2 active — — —
Windows 11 IPv6 stack active — — —

Root Cause

IPv6 Duplicate Address Detection (DAD) detected that the link-local address fe80::1 is already claimed by another host on the same link, preventing the interface from using that address.

generic

中文

IPv6重复地址检测（DAD）检测到链路本地地址fe80::1已被同一链路上的另一主机声明，阻止接口使用该地址。

Official Documentation

https://datatracker.ietf.org/doc/html/rfc4862

Workarounds

  1. 85% success Change the link-local address on one host by modifying the interface identifier: `ip link set dev eth0 address 02:00:00:00:00:01` (EUI-64 based), then reboot or restart networking. 
    Change the link-local address on one host by modifying the interface identifier: `ip link set dev eth0 address 02:00:00:00:00:01` (EUI-64 based), then reboot or restart networking.
  2. 90% success Use a static link-local address with a unique suffix on each host: `ip -6 addr add fe80::1/64 dev eth0` but ensure no conflict by checking with `ndp -a`. 
    Use a static link-local address with a unique suffix on each host: `ip -6 addr add fe80::1/64 dev eth0` but ensure no conflict by checking with `ndp -a`.
  3. 75% success Reconfigure the network to use globally routable IPv6 addresses instead of link-local for communication, and disable DAD for link-local only: `sysctl -w net.ipv6.conf.eth0.dad_transmits=0`. 
    Reconfigure the network to use globally routable IPv6 addresses instead of link-local for communication, and disable DAD for link-local only: `sysctl -w net.ipv6.conf.eth0.dad_transmits=0`.

中文步骤

  1. Change the link-local address on one host by modifying the interface identifier: `ip link set dev eth0 address 02:00:00:00:00:01` (EUI-64 based), then reboot or restart networking.
  2. Use a static link-local address with a unique suffix on each host: `ip -6 addr add fe80::1/64 dev eth0` but ensure no conflict by checking with `ndp -a`.
  3. Reconfigure the network to use globally routable IPv6 addresses instead of link-local for communication, and disable DAD for link-local only: `sysctl -w net.ipv6.conf.eth0.dad_transmits=0`.

Dead Ends

Common approaches that don't work:

  1. 95% fail

    Disabling DAD leads to network instability and packet loss as two hosts respond to the same address.

  2. 90% fail

    Both hosts will conflict; only one can respond to neighbor solicitations, causing intermittent failures.

  3. 80% fail

    Flushing caches does not resolve the underlying address duplication; the conflict persists.