MAC Address Table Design 187MAC Address TableDesignAll modules recognize two different kinds of addresses:n Static MAC addresses — Addresses that you manually add to thebridge address table using menu options. These addresses never age;you must add and remove them manually.n Dynamic MAC addresses — Addresses that the bridge learns byreceiving and processing frames and ages. In the bridge address table,each dynamic address is associated with a specific port and is assignedan age so that it can be cleared from the table if the station is inactive.Among all Switch 4007 modules, the address table design, learningprocess, and capacity are identical. The aging process differs slightlybetween Layer 2 Switching Modules and Multilayer Switching Modules.Address Space Each module can each store up to 32,768 addresses (32K):n In open VLAN mode, the address space is contiguous.n In closed VLAN mode, the address table is dynamically allocatedamong the VLANs so that in effect each VLAN operates with its ownaddress table.n The address threshold (Multilayer Switching Modules only) is the valueat which a module reports the total number of addresses that areknown. Specifically, when this threshold is reached, the modulegenerates the SNMP trap called addressThresholdEvent. The rangeof values you can enter for this parameter is between 1 and 1 plus themaximum address table size. If you do not want the module togenerate events, set address threshold to one greater than the addresstable; the threshold will never be reached.ImportantConsiderationsThe following address table considerations apply to all modules, unlessotherwise specified or unless the functionality described does not exist onyour module:n The address table is flushed any time that you cycle power to amodule or the chassis, reboot the module or chassis, or resetnon-volatile data.n Dynamic addresses are flushed whenever STP reconfigures thetopology.
