--- a/base/univention-system-setup/umc/python/setup/netconf/modules/SaveOldApplianceAddress.py	
+++ a/base/univention-system-setup/umc/python/setup/netconf/modules/SaveOldApplianceAddress.py	
@@ -19,6 +19,7 @@ class PhaseSaveOldApplianceAddress(AddressChange):
 		for name, iface in self.changeset.old_interfaces.ipv4_interfaces:
 			if ':' in name:
 				self.logger.info("Skipping %s...", name)
+				continue
 			ipv4 = iface.ipv4_address().ip
 			if ipv4 not in new_ipv4s:
 				self.rewrite(name, iface)