The value of tmnxPppPlcyMlpppEpMacAddress specifies the
class 3 address to use in the MLPPP Endpoint Discriminator Option.
While the value of tmnxPppPlcyMlpppEpClass is equal to 'macAddress',
a value of all zeroes specifies that the system MAC address be used;
otherwise, it means that no address is specified.