Chapter
3: Web Management
Security - Network - Limit Control
PoE Switch User Manual | 72
Aging Enabled
If checked, secured MAC addresses are subject to aging as discussed under Aging Period .
Aging Period
If Aging Enabled is checked, then the aging period is controlled with this input. If other
modules are using the underlying port security for securing MAC addresses, they may have
other requirements to the aging period. The underlying port security will use the shorter
requested aging period of all modules that use the functionality.
The Aging Period can be set to a number between 10 and 10,000,000 seconds.
To understand why aging may be desired, consider the following scenario: Suppose an
end-host is connected to a 3rd party switch or hub, which in turn is connected to a port on this
switch on which Limit Control is enabled. The end-host will be allowed to forward if the limit is
not exceeded. Now suppose that the end-host logs off or powers down. If it wasn't for aging,
the end-host would still take up resources on this switch and will be allowed to forward. To
overcome this situation, enable aging. With aging enabled, a timer is started once the
end-host gets secured. When the timer expires, the switch starts looking for frames from the
end-host, and if such frames are not seen within the next Aging Period, the end-host is
assumed to be disconnected, and the corresponding resources are freed on the switch.
Port Configuration
The table has one row for each port on the selected switch in the stack and a number of
columns, which are:
Port
The port number to which the configuration below applies.
Mode
Controls whether Limit Control is enabled on this port. Both this and the Global Mode must be
set to Enabled for Limit Control to be in effect. Notice that other modules may still use the
underlying port security features without enabling Limit Control on a given port.
Limit
The maximum number of MAC addresses that can be secured on this port. This number
cannot exceed 1024. If the limit is exceeded, the corresponding action is taken.
The stack is "born" with a total number of MAC addresses from which all ports draw
whenever a new MAC address is seen on a Port Security-enabled port. Since all ports draw
from the same pool, it may happen that a configured maximum cannot be granted, if the
remaining ports have already used all available MAC addresses.
