The value of tmnxPppoeSessionL2tpVrtrId indicates the connection
ID of the L2TP session associated with this PPPoE session.
The values of tmnxPppoeSessionL2tpVrtrId and
tmnxPppoeSessionL2tpConnectionId are the index in the table
TIMETRA-L2TP-MIB::tmnxL2tpSeStatusTable of the L2TP session associated
with this PPPoE session.
If there is no L2TP session associated with this PPPoE session, the
value of this object is equal to zero.