Fix vm config documentation

README.md

@@ -67,17 +67,18 @@ Interface attributes:
   interface.
 * *netmask* / *netmask6* - Netmasks for the above. The IPv4 netmask
   should have the full IP-like form (e.g. 255.255.255.0), while the
-  IPv6 netmask is expressed as the number of bits.
+  IPv6 netmask is expressed as the number of bits. Defaults are
+  respectively 255.255.255.0 and 64.
 * *additional_dns_names* - A list of additional unqualified DNS names
   for the gateway IP address that should be made available to VMs.
 
-DHCPv6 is automatically enabled if the interface has an IPv6 address.
-
 ### Virtual machines
 
 VM configuration files can specify the following attributes:
 
 * *ip* / *ip6* - IP addresses (IPv4 / IPv6) for static assignment.
+* *ram* - memory allocation (default *512m*)
+* *cpu* - CPU allocation (default *1*)
 * *volumes* - A list of space-separated volume specifications, which
   can be either:
   * a filename, which is interpreted as a QCOW2-formatted disk image,