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PLANET WGSD-10020 User Manual

Page 261

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User’s Manual of WGSD-10020 Series

261

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:

Object

Description

Port

The port number for 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 stackswitch 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.

Action

If Limit is reached, the switch can take one of the following actions:

None: Do not allow more than Limit MAC addresses on the port, but take no

further action.

Trap: If Limit + 1 MAC addresses is seen on the port, send an SNMP trap. If

Aging is disabled, only one SNMP trap will be sent, but with Aging enabled, new

SNMP traps will be sent everytime the limit gets exceeded.

Shutdown: If Limit + 1 MAC addresses is seen on the port, shut down the port.

This implies that all secured MAC addresses will be removed from the port, and

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