Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 318)

288 Multi-Service IronWare Switching Configuration Guide
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Backbone Edge Bridge (BEB) operation
11
MAC Learning for PBB Packets
PBB packets are MAC-in-MAC packets. There are two types of MAC learning involved depending on
whether the ISID involved in the received PBB packet is of any interest. If there is no such SI
configured for the PBB packet's B-VLAN and ISID, only the outer MAC (B-SA) is learned via the
regular Layer 2 MAC management for the corresponding B-VID. A regular Layer 2 endpoint must be
configured for each B-VLAN used as an IB-endpoint in a PBB instance.
If the PBB packet received has an SI configured that matches the B-VLAN and ISID of the packet's
PBB header, the inner MAC (C-SA) will be learned by the corresponding PBB instance and an
association is made between the C-SA to the B-SA of the received PBB packet. The B-SA
association under PBB is primarily used to program the hardware so that it knows how to set up the
PBB header for packets destined to the C-MAC that was associated with a particular B-MAC. The
B-DA of such packet forwarding will be set up according to this association. Another usage of this
B-SA association under PBB is to enable detection of B-MAC movement where the C-MAC
association to B-MAC may have changed from B-MAC-Z to B-MAC-T in
Figure 49 .
FIGURE 49 MAC Learning for PBB packets
L2 MAC Installment by PBB
When packet is being switched by the hardware based on the inner MACs (C-DA and C-SA), the
outer MACs (B-DA and B-SA) will stop hitting the regular Layer 2 CAMs programmed for the
associated B-SA. So without any intervention from PBB, these B-MACs once learned by the
corresponding Layer 2 B-VLAN, will start to age out. Once aged out, if another PBB packets is