Extreme networks Summit1 Manuale Utente

6-2

S

UMMIT

 S

WITCH

 I

NSTALLATION

 

AND

 U

SER

 G

UIDE

S

WITCH

 F

ORWARDING

 D

ATABASE

 (FDB)

switch is reset or a power off/on cycle occurs. For more information about setting 
the aging time, refer to the section 

,” later in this chapter.

 — If the aging time is set to zero, all aging entries in the database 

are defined as static, non-aging entries. This means that they do not age, but they are 
still deleted if the switch is reset.

 — Permanent entries are retained in the database if the switch is 

reset or a power off/on cycle occurs. The system administrator must make entries 
permanent. A permanent entry can either be a unicast or multicast MAC address. 
All entries entered by way of the command-line interface are stored as permanent. 
The switch can support a maximum of 64 permanent entries.

Once created, permanent entries stay the same as when they were created. For 
example. the permanent entry store is not updated when any of the following take 
place:

A VLAN is deleted

A VLANid is changed

A port mode is changed (tagged/untagged)

A port is deleted from a VLAN

A port is disabled

A port enters blocking state

A port QoS setting is changed

A port goes down (link down)

s — A blackhole entry configures packets with a specified MAC 

destination address to be discarded. Blackhole entries are useful as a security 
measure or in special circumstances where a specific destination address must be 
discarded. Blackhole entries are treated like permanent entries in the event of a 
switch reset or power off/on cycle. Blackhole entries are never aged out of the 
database.

Entries are added into the FDB in the following two ways:

The switch can learn entries. The switch updates its FDB with the source MAC 
address from a packet, the VLAN, and the port identifier on which the source packet 
is received.

You can enter and update entries using a MIB browser, an SNMP Network Manager, 
or the command-line interface, as described in the next section.

Summit.bk : 6FDB.FM  Page 2  Thursday, June 18, 1998  9:27 AM