3Com 4007, Руководство по внедрению, Страница: 187 / 684

MAC Address Table Design 187
MAC Address Table
Design
All modules recognize two different kinds of addresses:
■
Static MAC addresses — Addresses that you manually add to the
bridge address table using menu options. These addresses never age;
you must add and remove them manually.
■
Dynamic MAC addresses — Addresses that the bridge learns by
receiving and processing frames and ages. In the bridge address table,
each dynamic address is associated with a specific port and is assigned
an age so that it can be cleared from the table if the station is inactive.
Among all Switch 4007 modules, the address table design, learning
process, and capacity are identical. The aging process differs slightly
between Layer 2 Switching Modules and Multilayer Switching Modules.
Address Space Each module can each store up to 32,768 addresses (32K):
■
In open VLAN mode, the address space is contiguous.
■
In closed VLAN mode, the address table is dynamically allocated
among the VLANs so that in effect each VLAN operates with its own
address table.
■
The address threshold (Multilayer Switching Modules only) is the value
at which a module reports the total number of addresses that are
known. Specifically, when this threshold is reached, the module
generates the SNMP trap called
addressThresholdEvent
. The range
of values you can enter for this parameter is between 1 and 1 plus the
maximum address table size. If you do not want the module to
generate events, set address threshold to one greater than the address
table; the threshold will never be reached.
Important
Considerations
The following address table considerations apply to all modules, unless
otherwise specified or unless the functionality described does not exist on
your module:
■
The address table is flushed any time that you cycle power to a
module or the chassis, reboot the module or chassis, or reset
non-volatile data.
■
Dynamic addresses are flushed whenever STP reconfigures the
topology.