From Fedora Project Wiki

DHCPv6 switch to DUID-UUID


DHCP client and server should use RFC 6355 DUID UUID for DHCPv6 operations


  • Name: Pavel Zhukov
  • Email: <>
  • Release notes owner:

Current status

  • Targeted release: [[Releases/<number> | Fedora <number> ]]
  • Last updated: 2018-03-16
  • Tracker bug: <will be assigned by the Wrangler>

Detailed Description

Currently DUID LL(T) is used for IPv6 address assignment and prefix delegation. This lead to issues with devices which don't have hardware address assigned (like PPP) or devices which are not constantly assigned to the "server" (like wireless/usb devices etc). There are two main issues caused by this:

  1. Posible violation of RFC 3315
  2. DUID cannot be assembled due to lack of hardware address which leads dhclient to exit with error and manual intervention is required. Bug#626514
  3. DUID is changed between dhclient restarts as the result ISP doesn't delegate prefix which cause delays and connection outages Bug#1163379

Benefit to Fedora

Changing default to DUID UUID should solve mentioned issue and bring consistency within the distribution (NetworkManager uses DUID UUID from the beginning). As this change depends on systemd feature (machineid) it may be hard to get patches merged upstream


  • Proposal owners:
  • Other developers: N/A (not a System Wide Change)
  • Policies and guidelines: N/A (not a System Wide Change)
  • Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

This impact all installation which use dhclient to obtain ipv6 address or prefix. During the upgrade default duid changes from duid-ll to duid-uuid. Manual intervention is needed to protect old duid (or to update) is not decided yet.

How To Test

  1. DHCPv4 should continue operating as before TBD: check if client-identifier is affected by this change!
  2. Prefix Delegation over PPP MUST work without manual intervention
  3. DUID MUST NOT be changed between connections (client runs)
  4. DUID MUST NOT be changed as the result of physical device removal/system restart/system upgrade/

User Experience

Users which use IPv4 only should not be affected by the change. Users of IPv6 installations may need to notify their ISP about DUID changes or manually specify old DUID in leases file



Contingency Plan

  • Contingency mechanism: Revert back to current DUID.
  • Contingency deadline: N/A (not a System Wide Change)
  • Blocks release? N/A (not a System Wide Change), Yes/No
  • Blocks product? product


This is Fedora (systemd enabled systems) specific change so the documentation should be written and submitted upstream

Release Notes

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