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严格来说，redback bras链路聚合采用本地分配地址是不对，这个地址是链路聚合子层内部使用的私有mac。如果这个地址作为源地址发出去，就存在私有mac地址到处乱飞的情况。作为LAN还好说，作为MAN，或者多个BRAS使用链路聚合，就也可能存在MAC冲突的情况。
IEEE802.3标准中有明确说明，见下面红色部分文字。
43.2.1 Principles of Link Aggregation
Link Aggregation allows a MAC Client to treat a set of one or more ports as if it were a single port. In doing
so, it employs the following principles and concepts:
a) A MAC Client communicates with a set of ports through an Aggregator, which presents a standard
IEEE 802.3® service interface to the MAC Client. The Aggregator binds to one or more ports within
a System.
b) It is the responsibility of the Aggregator to distribute frame transmissions from the MAC Client to
the various ports, and to collect received frames from the ports and pass them to the MAC Client
transparently.
c) A System may contain multiple Aggregators, serving multiple MAC Clients. A given port will bind
to (at most) a single Aggregator at any time. A MAC Client is served by a single Aggregator at a
time.
d) The binding of ports to Aggregators within a System is managed by the Link Aggregation Control
function for that System, which is responsible for determining which links may be aggregated,
aggregating them, binding the ports within the System to an appropriate Aggregator, and monitoring
conditions to determine when a change in aggregation is needed.
e) Such determination and binding may be under manual control through direct manipulation of the
state variables of Link Aggregation (e.g., Keys) by a network manager. In addition, automatic determination,
configuration, binding, and monitoring may occur through the use of a Link Aggregation
Control Protocol (LACP). The LACP uses peer exchanges across the links to determine, on an ongoing
basis, the aggregation capability of the various links, and continuously provides the maximum
level of aggregation capability achievable between a given pair of Systems.
f) Frame ordering must be maintained for certain sequences of frame exchanges between MAC Clients
(known as conversations, see 1.4). The Distributor ensures that all frames of a given conversation are
passed to a single port. For any given port, the Collector is required to pass frames to the MAC Client
in the order that they are received from that port. The Collector is otherwise free to select frames
received from the aggregated ports in any order. Since there are no means for frames to be misordered
on a single link, this guarantees that frame ordering is maintained for any conversation.
g) Conversations may be moved among ports within an aggregation, both for load balancing and to
maintain availability in the event of link failures.
h) This standard does not impose any particular distribution algorithm on the Distributor. Whatever
algorithm is used should be appropriate for the MAC Client being supported.
[color=red]i) Each port is assigned a unique, globally administered MAC address. This MAC address is used as
the source address for frame exchanges that are initiated by entities within the Link Aggregation
sublayer itself (i.e., LACP and Marker protocol exchanges).
[/color]NOTE—The LACP and Marker protocols use a multicast destination address for all exchanges, and do not
impose any requirement for a port to recognize more than one unicast address on received frames.
j) Each Aggregator is assigned a unique, globally administered MAC address; this address is used as
the MAC address of the aggregation from the perspective of the MAC Client, both as a source
address for transmitted frames and as the destination address for received frames. The MAC address
of the Aggregator may be one of the MAC addresses of a port in the associated Link Aggregation
Group (see 43.2.10).