Featured content is also available via:

sysctl.d: enable promote_secondaries by default

System Internals / systemd - Tom Gundersen [jklm.no] - 25 July 2014 04:18 UTC

Without this, secondary addresses would get deleted when the primary one is. This is not the desired behavior when one would like to transition from one address to another in the same subnet (such as when a new IP address is given over DHCP).

In networkd, when given a new IP over DHCP we will add it, without explicitly removing the old one first (and hence never have a window without an IP address configured). Assuming the addresses are in the same subnet, that means that the old address is the primary and the new address is the secondary one. Once the old address expires, the kernel will drop it. With the old behavior this means that both addresses would be lost, which is clearly not what we want. With the new behavior, only the old address is lost, and the new one is promoted to primary.

Reported by Michael Olbrich

ad8bc9e sysctl.d: enable promote_secondaries by default
sysctl.d/50-default.conf | 3 +++
1 file changed, 3 insertions(+)

Upstream: github.com