I have this problem too with network-manager 1.6.0. For some reason the dhcp offer is rejected by dhclient when using network-manager.
Feb 5 16:25:12 erebor systemd[1]: Started Network Manager Wait Online. Feb 5 16:25:12 erebor dhclient[13084]: DHCPREQUEST of 192.168.1.35 on eth0 to 255.255.255.255 port 67 Feb 5 16:25:12 erebor dhclient[13084]: DHCPACK of 192.168.1.35 from 192.168.1.1 Feb 5 16:25:12 erebor dhclient[13084]: no expiry time on offered lease. Feb 5 16:25:12 erebor dhclient[13084]: Server added to list of rejected servers. Feb 5 16:25:13 erebor dhclient[13084]: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8 Feb 5 16:25:13 erebor dhclient[13084]: DHCPOFFER from 192.168.1.1 rejected by rule 192.168.1.1 mask 255.255.255.255. If I run dhclient on terminal the dhcp offer is accepted. The only difference I can see when running dhclient on terminal and when it's initiated by network-manager is the use of /usr/lib/NetworkManager/nm-dhcp-helper. I got the network-manager to work by changing the dhcp method to internal by adding line "dhcp=internal" to /etc/NetworkManager/NetworkManager.conf. IP addresses in my network are assigned by ZyWall 5.
