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I've configured a VPN connection and it created foo interface listed with ifconfig. Its IP is assigned via dhclient foo.

From time to time, my connection drops. When I list the available interfaces with ifconfig, there is foo without an IP and foo:avahi with a random IP.

If I request an IP with dhclient foo, an IP (generally same IP) is immediately fetched, my internet connection is fixed and the foo:avahi interface is disappeared.

What is this ...:avahi interface and how can I prevent this connection drops from happening?

  • Is other network configuration software, such as NetworkManager, running on your system? – grawity Feb 24 at 15:20
  • No, NetworkManager is totally uninstalled. I'm using my own network manager. – ceremcem Feb 24 at 15:32
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This isn't an interface; this is how old tools, namely ifconfig, show additional IP addresses on the eth0 interface (the kernel emulates an "interface alias" for every extra address).

The address/alias marked with "avahi" is created by avahi-autoipd, which implements RFC 3927 IPv4 link-local address autoconfiguration (also known as zeroconf or APIPA). The IP address isn't random; it's chosen from the reserved link-local prefix 169.254.0.0/16.

As for why this appears on its own, you'll need to actually check the system logs to find out; autoipd could be both the cause of the problems or it could be just the result of external problems.

  • It could be that some component in your system thinks no connection profile is active yet – because you've configured the IP address externally – so it deliberately switches into a "link-local only" profile and starts avahi-autoipd.

  • It could be that you first lose the connection, the DHCP client loses its address lease and is unable to obtain a new one, and some component on your system switches to "link-local mode" as a last resort only.

  • If the reason was loosing the connection first, then could the "link-local mode" be interpreted as "Currently we have no IP"? If so, is it correct to re-issue dhclient foo to get a new IP or is it only a workaround for a different problem? – ceremcem Feb 24 at 16:19

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