if(!res.isEmpty()){
sub = (DhcpSubnet) res.get(0);
} else {
Pair<String,Integer> cidrInfo = NetUtils.getCidr(network.getCidr());
sub = netBridge.addDhcpSubnet();
sub.subnetLength(cidrInfo.second());
sub.subnetPrefix(cidrInfo.first());
sub.defaultGateway(network.getGateway());
List<String> dcs = new ArrayList<String>();