Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 316)

286 Multi-Service IronWare Switching Configuration Guide
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Backbone Edge Bridge (BEB) operation
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FIGURE 47 S-VLAN keep mode with S-Tag insertion
PBB packet switching
There are several scenarios on how a packet is switched within the BEB.
• Packet may be switched between a local endpoint and an IB endpoint of the SI.
• Packet may be switched between two local endpoints of the SI.
• Packet may be switched between two IB endpoints where the BEB is acting as a BCB.
• Unknown C-DA packets flooding handling.
PBB Packet Received at the IB endpoint
When the sender does not know where the C-DA is located, the packet is flooded with the
configured flooding B-DA over the B-VLAN configured for the respective SI. If the sender knows
which BEB owns the intended C-DA (C-DA was learnt and associated with a particular BEB's B-MAC),
it will send the packet to that destination BEB.
Unknown Destination PBB Packet Handling
When a BEB receives a PBB packet with the default backbone multicast destination address as its
B-DA and the corresponding ISID is of interest (it has configuration of SI that has matching BVLAN
and ISID), it will examine the packet to determine if the associated C-DA in the PBB packet is a
known MAC address. If it is known, it will forward the packet to the port that learned the C-MAC. If
the C-DA is also unknown to the BEB that received this PBB packet, it will need to flood this packet
to all its local endpoints as well as to all the IB-endpoints of the corresponding SI. When such
flooding occurs, the packet destined towards the PBB networks will retain the original received PBB
header without any modification. The default backbone multicast destination MAC address is
constructed by concatenating the three octet OUI 00-1E-83 with the three octet I-SID (and asserting
the I/G bit to signify a group MAC address). The resulting B-DA is shown in
Figure 48 .