+ @staticmethod
+ def get_interface_ip4_prefix_length(node, iface_key):
+ """Get IP4 address prefix length for the interface.
+
+ :param node: Node to get prefix length on.
+ :param iface_key: Interface key from topology file.
+ :type node: dict
+ :type iface_key: str
+ :returns: Prefix length from topology file or the default
+ IP4 prefix length if not found.
+ :rtype: int
+ :raises: KeyError if iface_key is not found.
+ """
+ return node[u"interfaces"][iface_key].get(u"ip4_prefix_length", \
+ Constants.DEFAULT_IP4_PREFIX_LENGTH)
+