Its a good chance to explain what and how configure the ping node.
First, Ping node can be a server, router or any device that can be pinged.
And here how it's working:
Lets say you have 2 servers (A&B) you connect them thru connection 1, then you have a second connection from each server to the ping node.
You set your replication task and your virtual IP address. Then, start the Autofailover. Now, lets test those scenarios:
1- If the connection 1 failed. Server A is going to check with the Ping node if server B is up or not. Or if its just the connection get dropped.
2- If the connection failed between server A and the ping node. Server B is going to check thru connection 1 and see if the server A is up.
3- If the connection between B and ping node failed, server A will check if B is up from connection 1.
You can see here that the Ping node is the Heart Beat of the process. And its not a single point of failure. Actually, it provides reliability for the process.