3Com 1000 User Manual

Also see for SuperStack 3 WEBCACHE 1000: User guide Mounting guide Release notes User guide

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4-16 C HAPTER 4: M ANAGING T HE S WITCH 1000Setting Up the Switch Database (SDB)The Switch maintains a database of device addressesthat it receives on its ports. It uses the informationin this database to decide whether a frame shouldbe forwarded or filtered. The database holds up to amaximum of 500 entries; each entry consists of theMAC address of the device and an identifier for theport on which it was received.If you have set up Traps for the Switch, notificationthat the database is becoming full is provided bytwo traps:n Database is 90% fulln Database is 100% fullThese traps indicate that the maximum number ofdevices which can be connected to the Switch hasbeen reached. You cannot connect any more devicesto the Switch. Additional devices can, however, beconnected to the rest of the network.Entries are added into the Switch Database in twoways:n The Switch can learn entries. That is, the unitupdates the SDB with the source MAC address,and the port identifier on which the source MACaddress is seen. Addresses are not learned onthe backbone port. Learning is affected by secu-rity (refer to the description for the Security fieldon page 4-13).n The system administrator can enter and updateentries using a MIB browser, an SNMP NetworkManager or the Switch Database screendescribed in the following sections.There are three types of entries in the SDB:n Ageing entries — Initially, all entries in the data-base are ageing entries. Entries in the databaseare removed (aged out) if, after a period of time(ageing time), the device has not transmitted.This prevents the database from becoming fullwith obsolete entries by ensuring that when adevice is removed from the network, its entry isdeleted from the database. Ageing entries aredeleted from the database if the Switch is resetor a power-off/on cycle occurs. For more informa-tion about setting an ageing time, refer to “Set-ting Up the Switch Unit” on page 4-9.n Non-ageing entries — If the ageing time is setto 0:00, all ageing entries in the database aredefined as non-ageing entries. This means thatthey do not age, but they are still deleted if theSwitch is reset or a power off/on cycle occurs. Formore information about setting an ageing time,refer to “Setting Up the Switch Unit” on page4-9.n Permanent entries — Permanent entries donot age, and they are retained in the database ifthe Switch is reset or a power-off/on cycle occurs.