The tmnxOamMacPingReplyIndex is unique within a group of responses
received as the result of a OAM 'macPing' probe as specified by
having the same value for tmnxOamMacPingHistoryIndex.
The agent starts assigning tmnxOamMacPingReplyIndex values at 1
and wraps after exceeding the maximum possible value as defined by
the limit of this object.