Can ESXi 5.5 be managed by vCenter 5.1?
No vCenter 5.1 does not support ESXi 5.5You need to upgraded the vcenter to 5.5 atleast to support it.
Check the screenshot below
No vCenter 5.1 does not support ESXi 5.5You need to upgraded the vcenter to 5.5 atleast to support it.
Check the screenshot below