Health Monitor Issue

The SEND string that has been configured as a monitor is actually related to monitoring the services (LAYER 4) on the pool members, whereas the ping monitor checks the availability (LAYER 3 ) of the nodes forming that pool. The services may be down even if the nodes are UP. Imagine a situation in which you have built the server and assigned it an IP address which is pinging from F5 (In this case the ping monitor will show the pool to be UP). But no services or your application has been configured and hence you will not get services out of that server( the pool would be down as per the customised monitor).