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2. An AMP/SMP MAC frame with the A/C bit set B′0′ is seen. This indicates
that there is only one station attached to this port and the address of that
station is one which is seen in the AMP/SMP MAC frame with the A/C bit set
to B′0′. In this case, the AMP/SMP MAC frame sent by the upstream station
is copied by the station attached to this port. Then the station attached to
this port has issued its own AMP/SMP MAC frame which will pass this Ring
Monitor with the A/C bit set to B′0′. The source address in this AMP/SMP
MAC frame is the address of the station attached to this port.
3. Several AMP/SMP MAC frames with the A/C bit set to B′1′ are seen followed
by an AMP/SMP MAC frame with the A/C bit set B′0′.
This indicates that there are several stations attached to this port via a
fan-out device and the addresses of these stations are the source addresses
in the AMP/SMP MAC frames.
In this case, the AMP/SMP MAC frame sent by the upstream station is
copied by the station attached to the first port of the fan-out device and the
AMP/SMP MAC frame issued by that station is subsequently copied by the
station attached to the second port of the fan-out device and so on. The
source addresses in all the AMP/SMP MAC frames with the A/C bit set to
B′1′ plus the source address of the AMP/SMP MAC frame with the A/C bit
set to B′0′ show addresses of the stations attached to this port (via the
fan-out device) and are used by the Ring Monitor to build the address-to-port
map for this port.
Note
A fan-out device may support more than 8 stations which will result in the
Ring Monitor seeing as many AMP/SMP frames as the number of
stations. However, the Ring Monitor will only save the address of the
first eight stations.
The AMP/SMP issued by the last (or the only) station on each port will pass the
Ring Monitor function on that port and will immediately be seen by the Ring
Monitor function on the next port downstream from this port. As soon as the
Ring Monitor on the downstream port sees this AMP/SMP MAC frame with the
A/C bit set to B′0′, it moves downstream of its associated port and will then
signal the Ring Monitor on the upstream port which currently is situated
downstream of its associated port to move to the upstream of its associated port
to prepare for the next round of neighbor notification as well as assisting the
Recovery ASIC with the beacon recovery process.
The above procedure will be repeated on all the ports helping the Recovery
ASIC to build an accurate address-to-port map for all the ports on the module.
An example of the output for this command is shown in Figure 103 on page 166.
Chapter 8. 8260 Token-Ring Support 165