3Com 5500-SI Configuration Manual page 453

Setting MAC Address Aging Time
Setting an appropriate aging time implements MAC address aging. Too long or too
short an aging time set by subscribers will cause the Ethernet switch to flood a large
amount of data packets. This affects the switch operation performance.
If the aging time is set too long, the Switch will store a great number of out-of-date
MAC address tables. This will consume MAC address table resources and the Switch
will not be able to update the MAC address table according to the network change.
If the aging time is set too short, the Switch may delete valid MAC address table
entries.
You can use the following commands to set the MAC address aging time for the
system.
Perform the following configuration in System View.
Table 498 Set the MAC Address Aging Time for the System
Operation
Set the dynamic MAC address aging time
Restore the default MAC address aging time undo mac-address timer aging
In addition, this command takes effect on all the ports. However the address aging
only functions on the dynamic addresses (manual entries added to the Switch are not
aged).
By default, the
aging-time
command performs no aging on the MAC address entries.
Setting the Max Count of MAC Addresses Learned by a Port
With the address learning function, a Switch can learn new MAC addresses. After its
received a packet destined for an already learned MAC address, the Switch will
forward it directly with the hardware, instead of broadcasting it. However, too many
MAC address items learned by a port will affect the Switch operation performance.
You can control the MAC address items learned by a port through setting the max
count of MAC addresses learned by a port. If a user sets the max count value of a port
as , the port will not learn new MAC address items when the count of MAC
count
address items reaches the
You can use the following commands to set the max count of MAC addresses learned
by a port.
Perform the following configuration in Ethernet Port View.
Table 499 Set the Max Count of MAC Address Learned by a Port
Operation
Set the Max Count of MAC Address
Learned by a Port
Restore the default Max Count of MAC
Address Learned by a Port
By default, there is no limit to the MAC addresses learned using the Ethernet port.
MAC Address Table Management 453
Command
mac-address timer { aging age |
no-aging }
is 300 seconds. With the
value.
count
Command
mac-address max-mac-count count
undo mac-address max-mac-count
parameter, the
no-aging