public List<String> findUnusedIpAddresses(NodeList nodes) {
            List<String> unusedAddresses = new ArrayList<>(ips());
            nodes.matching(node -> node.ipConfig().primary().stream().anyMatch(ip -> ips().contains(ip)))
                 .forEach(node -> unusedAddresses.removeAll(node.ipConfig().primary()));
            return unusedAddresses;
        }
Finds all unused IP addresses in this pool

@param nodes a list of all nodes in the repository
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/node/IP.java