Hi Aurelien, I am using both systemd and sysvinit-core, but I am not sure which one was active when I ran into this problem.
Consider a split DNS setup for a remote network. I had started an IPsec connection to the remote side. /etc/resolv.conf was changed to include the new internal DNServer on the remote side, but a host lookup gave me still the old external address. Stopping nscd did not help, AFAIR. See also #895977 (resolvconf). Regards Harri