Optical Systems Design OSD2524, User Manual

Page: 89 / 402

OPTICAL SYSTEMS DESIGN
DOC ID: 10120001
OSD2524 OPERATOR MANUAL
PAGE 89
This page allows you to configure the Port Security Limit Control system and port settings.
Limit Control allows for limiting the number of users on a given port. A user is identified by a
MAC address and VLAN ID. If Limit Control is enabled on a port, the limit specifies the
maximum number of users on the port. If this number is exceeded, an action is taken. The
action can be one of the four different actions as described below.
The Limit Control module utilizes a lower-layer module, Port Security module, which manages
MAC addresses learnt on the port.
The Limit Control configuration consists of two sections, a system- and a port-wide.
SYSTEM CONFIGURATION
Mode
Indicates if Limit Control is globally enabled or disabled on the switch. If globally disabled, other
modules may still use the underlying functionality, but limit checks and corresponding actions are
disabled.
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 switch 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.