Cisco Exam 300-425 Topic 9 Question 14 Discussion

An enterprise is using the wireless network as the mam network connection for corporate users and guests To ensure wireless network availability, two standalone controllers are installed in the head office APs are connected to the controllers using a round-robin approach lo load balance the traffic After a power cut, the wireless clients disconnect while roaming An engineer tried eping from the controller but fails Which protocol needs to be allowed between the networks that the controllers are Installed?