How to get change in network connection notification from iOS Reachability Class?

Hi I want to capture whenever user gets a network connectivity in my application for this I have added apples Reachability class and below is the snippet I am using in my appDelegate class didFinishLaunchingWithOptions method,

Reachability* reachability = [Reachability reachabilityForInternetConnection];
        [reachability startNotifier];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];

and my reachabilityChanged selector method is as below

- (void)reachabilityChanged:(NSNotification*)notification
{
    Reachability* reachability = notification.object;
    if(reachability.currentReachabilityStatus == NotReachable)
        NSLog(@"Internet off");
    else
        NSLog(@"Internet on");
}

but here I am not getting any kind of notification when I switch off my Airplane mode and when I get a network connectivity in my phone.

Am I missing anything?