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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter26 Configuring Fallback Bridging
Configuring Fallback Bridging
Configuring the Bridge Table Aging Time
A switch forwards, floods, or drops packets based on the bridge table. The bridge table maintains both
static and dynamic entries. Static entries are entered by you or learned by the switch. Dynamic entries
are entered by the bridge learning process. A dynamic ent r y is au toma tic al ly re m oved af ter a spec ifi ed
length of time, known as aging time, from the time the entry was created or last updated.
If you are likely to move hosts on a switched network, decrease the aging-time to enable the switch to
quickly adapt to the change. If hosts on a switched network do not continuously send packe ts, i ncre ase
the aging time to keep the dynamic entries for a longer time and thus reduce the possibility of flooding
when the hosts send again.
Beginning in privileged EXEC mode, follow these steps to configure the aging time:
To return to the default aging-time interval, use the no bridge bridge-group aging-time global
configuration command.
This example shows how to change the bridge table aging time to 200 seconds for bridge group 10:
Switch(config)# bridge 10 aging-time 200
Filtering Frames by a Specific MAC Address
A switch examines frames and sends them through the internetwork according to the destination address;
a switch does not forward a frame back to its originating network segme nt. You can use the software to
configure specific administrative filters that filter frames based on information other than the paths to
their destinations.
You can filter frames with a particular MAC-layer station destination address. Any num ber of addre sses
can be configured in the system without a performance penalty.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 bridge bridge-group aging-time seconds Specify the length of time that a dynam ic en try rema ins i n t he b ri dge
table from the time the entry was created or last updated.
•For bridge-group, specify the bridge group number. The range is 1
to 255.
•For seconds, enter a number from 0 to 1000000. The default is 300
seconds.
Step3 end Return to privileged EXEC mode.
Step4 show running-config Verify your entry.
Step5 copy running-config startup-config (Optional) Save your entry in the configuration file.