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device on that port and therefore, the Recovery ASIC will be able to build the
address-to-port map by listening to neighbor notification process as described
above.
Figure 99. Address-to-port Mapping on Module Switching Modules for Fan-Out Attached
Devices
Now, let′s assume that a second station (station ″C″) attaches to the fan-out
device. In the next neighbor notification process the Recovery ASIC will detect
that there is a new MAC address (station ″C″) in the ring but there is no new
phantom voltage raised. It, therefore, assumes that the new station is attached
to a port which already has a raised phantom signal (that is, the new station is
attached via a fan-out device). By looking at its current address-to-port map, the
Recovery ASIC can determine between which two existing MAC addresses the
new MAC address has been inserted. In this example, they would be station ″B″
and station ″D″. If these two MAC addresses are on two different ports (which is
the case in this example), it concludes that the new MAC address must be on
the port associated with one of those two MAC addresses. The Recovery ASIC,
then wraps all the ports on the module and the backplane and tests each of the
two suspected ports individually by sending a Duplicate Address Test MAC
frame to the new address. The received frame will be examined to see if the
A/C bits are set to B′1′. If yes, then the station is on that port, and the Recovery
ASIC will update its address-to-port map and then unwraps all ports.
An example of the ″ring_map″ display for a module switching module with a
fan-out device attached to port 2 is shown in Figure 100 on page 163. Note that
there were two stations attached to the fan-out device when this display was
taken.
162 8260 Multiprotocol Intelligent Switching Hub