Any change in the usage of MAC addresses will not happen unless it is explicitly configured. This will prevent you from experiencing unexpected behavior resulting from a system change.
Except for using a different MAC address, this feature does not change the way PPPoE works. This change is limited to ATM interfaces only--specifically, PPPoEoA--and will not be applied to other interfaces where PPPoE is operated such as Ethernet, Ethernet VLAN, and Data-over-Cable Service Interface Specifications (DOCSIS). Changing the PPPoE MAC address on those interfaces, which are broadcast in nature, requires placing the interface in promiscuous mode, thereby affecting the performance of the router because the router software has to receive all Ethernet frames and then discard unneeded frames in the software driver.
This feature is disabled by default and applies to all PPPoE sessions on an ATM interface configured in a BBA group.
When PPPoE and RBE are configured on two separate ATMs on the same DSL, the customer premises equipment (CPE) acts like a pure bridge, bridging from Ethernet to the two ATMs on the DSL. Because the CPE acts as a bridge, and because the aggregation router uses the same MAC address for both PPPoE and RBE, the CPE will not be able to bridge packets to the correct MAC address. The solution is to have a different MAC address for PPPoE only. The MAC address can be either configured or selected automatically.
The MAC address of the PPPoEoA session is either the value configured on the ATM interface using the mac-address command or the burned-in MAC address if a MAC address is not already configured on the ATM interface. This functionality is effective only when neither autoselect nor a MAC address is specified on a BBA group.
If the MAC address is specified on a BBA group, all PPPoEoA sessions use the MAC address specified on the BBA group, which is applied on the VC.
If the MAC address is selected automatically, 7 is added to the MAC address of the ATM interface.