HP J2415A Installation And Reference Manual page 53

Installing and Using HP Stack Manager
Interoperability with Pre-Standard IEEE 802.12 100VG Devices
The IEEE 802.12 standard specifies that null address training should not be
successful. To be interoperable with pre-standard devices which may
depend on null address training, HP Stack Manager, HP Interconnect
Manager, and the ASCII console have added an option. In HP Stack
Manager's Port Security Configuration dialog box, the option is called
"Prevent Training with Null Address". The default is to allow null address
device training. If you change this option to disallow null address training,
be aware that some pre-standard devices (e.g., pre-standard LAN adapters),
may need to be upgraded (for example, a new driver may need to be
installed).
Once the port has been assigned or has learned an authorized address, only
that address will be allowed to pass training at the port. Any other address
(including null) will fail training. This is true regardless of how the Null
Address option is selected. However, if you have updated the device (e.g.,
LAN adapter) to be compatible with the IEEE 802.12 standard, then you can
use any of the security options.
After you have selected how the MAC address is to be authorized, you need
to specify the type of training allowed:
Private mode is when an end node or a port on the hub receives only
packets specifically addressed to it. Private mode is recommended for
typical end node to end node communications such as file server to client
communications. Private mode provides security against promiscuous
listening.
Cascade mode allows repeaters connected to the port to receive all traffic,
as they need to. Any other type of device that trains on the port will be
automatically restricted to Private mode listening.
Any Device allows any device such as a private end-node, switch, network
analyzer, or a repeater to train. This mode provides no security against
promiscuous listening.
Thorough training descriptions are described in the included
HP 100VG-AnyLAN Technology Guide. Because training and address
security are related, you can set up both types of security from the Port
Security Configuration dialog in HP Stack Manager.
Note that 100VG will not transmit unicast packets except to promiscuous
end-nodes or nodes with the matching address. Thus, private end-nodes are
prevented from eavesdropping.
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