0
  • Added support for detecting duplicate IPv4 addresses, with a timeout configurable through the ipv4.dad-timeout connection property.

-- NEWS


dad-timeout / int32 / -1

Timeout in milliseconds used to check for the presence of duplicate IP addresses on the network. If an address conflict is detected, the activation will fail. A zero value means that no duplicate address detection is performed, -1 means the default value (either configuration ipvx.dad-timeout override or zero). A value greater than zero is a timeout in milliseconds. The property is currently implemented only for IPv4.

-- IPv4 Settings

Quote taken from the manual for NetworkManager, as of version 1.14.4.

I failed to find ipvx.dad-timeout documented anywhere. It is described as an "override", not a default. So it sounds more likely that ipvx.dad-timeout is not set by default. In other words, the default is not to enable IPv4 Duplicate Address Detection. Is that right?

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These properties are generally part of the connection profile. However, some of these properties have a special value that indicates the "default" value. For those, the default value may be configured in NetworkManager.conf. Consequently, that's documented in man NetworkManager.conf -- as opposed to man nm-settings.

But note that the default value in NetworkManager.conf only matters if you don't specify an explicit value in the profile itself. The profile's value has precedence.

"-1 means the default value (either configuration ipvx.dad-timeout override or zero)" means that -1 is the default value for this property in the profile. This allows fallback to a configured default value in NetworkManager.conf, and in case that it is still unspecified there, the final value 0 (disabled) is used.

  • Ahh. I see there is not a literal setting ipvx.dad-timeout, but there is a global setting ipv4.dad-timeout corresponding to the connection setting ipv4.dad-timeout. (And the same for ipv6, except the setting is not implemented for ipv6 yet anyway, which is why it is not mentioned in the current version of man NetworkManager.conf). – sourcejedi Feb 6 at 23:14
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By default the parameter is set to -1 , you can check it through :

nmcli con show "connexion_name" | grep ipv4.dad-timeout

Use the nmcli con show to get the name of the connexion.

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