On a desktop Debian Jessie GNU/Linux install, the file /etc/resolvconf/update-libc.d/avahi-daemon contains:

# If we have an unicast .local domain, we immediately disable avahi to avoid
# conflicts with the multicast IP4LL .local domain

if [ -x /usr/lib/avahi/avahi-daemon-check-dns.sh ]; then
  exec /usr/lib/avahi/avahi-daemon-check-dns.sh

However, neither man avahi-daemon.conf nor man avahi-daemon mention IP4LL.

Wikipedia does not currently mention IP4LL.

Web searches show few hits. This page in the Tin Hat GNU/Linux "Quickstart" manual gives a little information:

Tin Hat assumes that your system has up to four NIC cards, eth0 through eth3. It will try to configure each one using DHCP first and, failing that, will assign an IP4LL address. ...

A thread on the avahi-autoipd mailing list gives a bit more information:

Avahi 0.6.14 will ship with its own implementation of IP4LL (rfc3927). ...

However, RFC 3927 has no mention of the term "IP4LL". It does, however, use the term "IPv4 Link-Local".

Also, the blurb for Cozybit's "Zeroconf module" refers to "IP4LL (Link Local)".

Unfortunately, none of this seems very definitive. Hence my question: what is "IP4LL"? Is it just an abbreviated way of writing "IPv4 Link-Local"? If it is, I would be grateful for a reliable reference to back this up. If it isn't, then what does it refer to?

1 Answer 1


Yes, it's just an abbreviation for IPv4 link-local. See for example IPv4LL Compliance Testing.

  • Thanks, but I'm afraid the page you linked to does not mention "IP4LL". It does, however, mention "IPv4LL". Are you aware of any reliable sources that equate IP4LL to IPv4LL? I am wary of assuming them to be the same thing, in the absence of a definitive statement to the effect that they are.
    – user6860
    Oct 12, 2016 at 14:55
  • I'm not sure what you'd consider reliable, and yes, I was equating IPv4LL and IP4LL there. A web search shows a number of hits for IP4LL, nothing that jumps out as being particularly authoritative though (but nothing authoritative that uses IP4LL in any other way either). Oct 12, 2016 at 15:31
  • Reliable sources might include: the technical manual for a widely used product from a reputable person or organisation, or a book or article from a reputable publisher. However, I am starting to wonder if "IP4LL" is just an accidental abbreviation of "IPv4LL", in which case "IP4LL" probably would not appear in such sources as I consider reliable. So, I may have to settle for a lower standard of evidence. Do you have any other reason (e.g. professional experience) that makes you confident "IP4LL" refers to "IPv4 Link-Local"? Thanks again.
    – user6860
    Oct 12, 2016 at 16:50
  • Since this answer was posted, I haven't seen anything to contradict it, and the sources in my question appear to be about as reliable as may exist. Therefore, instead of holding out for any more reliable sources, I will tentatively mark this answer as correct. Thanks for your patience!
    – user6860
    Nov 8, 2016 at 14:35
  • No worries, I meant to come back to it... It's still on my to-do list! Nov 8, 2016 at 14:39

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