The value of tmnxOamMfibPingCtlDestMacAddr specifies the IPv6
multicast MAC address to be used as the destination for performing an
OAM ping operation when tmnxOamPingCtlTestMode has a value of
'mfibPing' and objects tmnxOamMfibPingCtlSrcAddrType and
tmnxOamMfibPingCtlDestAddrType have a value of 'unknown (0)',
in which case this parameter is required. If tmnxOamPingCtlTestMode is
different from 'mfibPing' this field is ignored.