DHCP_CLIENT = 'dhclient|dhcpcd'
            : 'use either dhclient or dhcpcd'
DHCP_IF     = 'IP_NET_[1-9][0-9]*_DEV'
            : 'invalid dhcp interface specification, only references to IP_NET_x_DEV are allowed'
DHCP_ROUTES = 'imond|default|none'
            : 'invalid route value, only imond, default or none are allowd'
+IP_NET(OPT_DHCP_CLIENT) = 'dhcp' 
	    : ', or dhcp, if the interface is configured by dhcp'