MN700004 Rev 01 10411. Forwarding Database (FDB)IntroductionThe MAC Address table contains the information that is in the forwarding database. Theswitch uses the forwarding database to forward packets to the appropriate bridge in the bridgegroup.The FDB has both static entries, which are created by the user, and dynamic entries (learnedentries), which are added and removed by the learning process. Static entries cannot beoverwritten by the learning process, and are removed from the table only when you explicitlydelete them.MAC-Table Entry TypesThere are several types of entries in the FDB (forwarding Database Table):• Dynamic entries −Initially, all entries in the database are dynamic. Entries inthe database are removed (aged-out) if, after a period of time (aging time), thedevice has not transmitted. If a device is removed from the network, its entryis deleted from the database. In this way, the database is not filled up withobsolete entries. If the switch is reset or a power Off/On cycle occurs,dynamic entries are deleted from the database. The dynamic entries can alsobe deleted by a specified command. More information about setting the agingtime and deleting dynamic entries is provided further on in this section.• Static entries − Static entries are configured by the user. These arepermanent entries which are retained in the database if the switch is reset or apower off/on cycle occurs. The system administrator is responsible formaking entries permanent. A permanent entry can be a unicast MAC address.All entries entered by way of the command-line interface are stored aspermanent.• Secure entries −A secure entry is configured to a secured port (configured bythe port security command as described in the Port Security chapter),allowing only secured MAC addresses to be learned by this port.• Self entries – A self entry is created automatically for each VLAN that isconfigured on the switch with the switch's MAC address.• Filtered entries –Filtered entries are dynamic MAC addresses that performsecurity violation on secured port (configured by the port securitycommand).
