VULTR has recently made changes on their end, and everything should now work fine 'out of the box' with NetworkManager enabled. Should you wish to disable NetworkManager, you can follow these steps.
Pasted below is an example /etc/sysconfig/network-scripts/ifcfg-eth0 file. This template configures IPv4/IPv6 statically. Substitute DNS/HWADDR/IPADDR/GATEWAY/IPV6ADDR from your existing configuration.
DNS1=123.123.123.123
ONBOOT=yes
BOOTPROTO=static
DEVICE=eth0
HWADDR=52:54:00:00:00:00
IPADDR=123.123.123.123
PREFIX=23
GATEWAY=123.123.123.123
DEFROUTE=yes
NM_CONTROLLED=no
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6ADDR="2001:1234:1234:1234::64/64"
IPV6_AUTOCONF=yes
IPV6_FAILURE_FATAL=no
Then, disable NetworkManager and restart networking:
systemctl stop NetworkManager
systemctl disable NetworkManager
systemctl restart network
Don't forget, should you lose access to your box you can use the VNC console from the control panel.
