diff --git a/utils/he_ipv6/tunnel.py b/utils/he_ipv6/tunnel.py
index 8237f05..cd134c2 100644
--- a/utils/he_ipv6/tunnel.py
+++ b/utils/he_ipv6/tunnel.py
@@ -129,15 +129,15 @@ class Assignment(object):
         self.alloc_block = self.alloc.ip.alloc_block
         self.iface_blocks = self.alloc_block.extract_subnet(self.prefix, count = 1)
         logger.debug('Allocation blocks for {0}: {1}'.format(self.iface, ','.join([str(i) for i in self.iface_blocks])))
-        for i in self.iface_blocks:
+        for idx, i in enumerate(self.iface_blocks):
             # DHCPv6 range.
-            _base = str(i.ip).rstrip(':')
+            _base = '{0}:{1}'.format(str(i.ip).rstrip(':'), idx)
             logger.debug('Base prefix for {0}: {1}'.format(str(i), _base))
             start = '{0}:dead:beef:cafe:0'.format(_base)
             stop = '{0}:dead:beef:cafe:ffff'.format(_base)
-            range = (start, stop)
-            self.dhcp6_ranges.append(range)
-            logger.debug('Added range {0} to block {1} for iface {2}'.format(range, str(i.ip), self.iface))
+            d_range = (start, stop)
+            self.dhcp6_ranges.append(d_range)
+            logger.debug('Added range {0} to block {1} for iface {2}'.format(d_range, str(i.ip), self.iface))
         return(None)