To prevent customers from experiencing unexpected behavior resulting from a system change, any change in the usage of MAC
addresses will not happen unless it is explicitly configured.
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 on interfaces
such as Gigabit 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 Gigabit 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 PVC interface configured in a BBA group.
When PPPoE and Rapid Bandwidth Expansion (RBE) are configured on two separate PVCs on the same DSL, the customer premises
equipment (CPE) acts like a pure bridge, bridging from Gigabit Ethernet to the two ATM PVCs 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 PVC. 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 broadband access group (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.