Uri addr = new Uri("http://localhost:8081/TestService");
try
{
    ServiceHost host = new ServiceHost(typeof(TestService), addr);

    host.AddServiceEndpoint(typeof(ITestService), new WSHttpBinding(), addr);

    ServiceMetadataBehavior mdb = host.Description.Behaviors.Find<ServiceMetadataBehavior>();
    if (mdb == null)
    {
        mdb = new ServiceMetadataBehavior();
        mdb.HttpGetEnabled = true;

        host.Description.Behaviors.Add(mdb);
    }
    host.AddServiceEndpoint(typeof(IMetadataExchange), new BasicHttpBinding(), "mex");

    service.ConnectionString = con;
    host.Open();
    aL.Add(host);
}
catch(Exception ex)
{
    System.Windows.Forms.MessageBox.Show(ex.Message);
}

 <soap12:address location="http://localhost:8081/TestService" /> 

//У сервера  2  IP и отвечать он должен на запросы из обоих сетей
host.AddServiceEndpoint(typeof(ITestService), new WSHttpBinding(), "http://10.240..71:8081/TestService");
host.AddServiceEndpoint(typeof(ITestService), new WSHttpBinding(), "http://10.200..129:8081/TestService");

<soap12:address location="http://localhost:8081/TestService" />