How to develop an asynchronous mechanism to test pings?

I'm having a slowness problem with a transaction that pings to see if certain IP's are accessible. It turns out that this transaction tests more than 20 different IP's, which makes the total transaction time is 2 minutes. To decrease the total time of this transaction, I tried to implement asynchronous methods to test these IPs simultaneously, but I did not succeed. Here is the code implemented so far.

    public async Task<List<Foo>> Testar(List<Foo> lista)
    {
        Task<Foo>[] teste = new Task<Foo>[lista.Count];
        for (int i = 0; i < lista.Count; i++)
        {
            teste[i] = Verificar(lista[i].IP);
        }

        for (int i = 0; i < lista.Count; i++)
        {
            lista[i].Status = await teste[i];
        }

        return lista;
    }

    public async Task<Status> Verificar(string ip)
    {
    int retorno = await TestarIP(ip);
    return ((Status)retorno); 
    }


    public async Task<int> TestarIP(string ip)
    {            
        if(new Ping().Send(ip, timeOutPing).Status.Equals(IPStatus.Success))
            return 1;
        else 
            return 2;
    }

The code runs as soon as the page loads (in onLoad), but even using Async / Await, is having the same runtime as before. So how can I create threads to test these ip's simultaneously?