--- a/cloudinit/net/cmdline.py
+++ b/cloudinit/net/cmdline.py
@@ -86,6 +86,9 @@
         else:
             proto = 'static'
 
+    if proto == 'dhcp6':
+        proto = 'dhcp'
+
     if proto not in ('static', 'dhcp'):
         raise ValueError("Unexpected value for PROTO: %s" % proto)
 
@@ -98,8 +101,8 @@
     if name in mac_addrs:
         iface['mac_address'] = mac_addrs[name]
 
-    # originally believed there might be IPV6* values
-    for v, pre in (('ipv4', 'IPV4'),):
+    # Handle both IPv4 and IPv6 values
+    for v, pre in (('ipv4', 'IPV4'), ('ipv6', 'IPV6')):
         # if no IPV4ADDR or IPV6ADDR, then go on.
         if pre + "ADDR" not in data:
             continue