User’s Manual of NS3550-24T/4S
235
The page includes the following fields:
System Configuration
Object
Description
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 weren’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, 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 switch 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 an address 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
no new will be learned. Even if the link is physically disconnected and
reconnected on the port (by disconnecting the cable), the port will remain shut
down. There are three ways to re-open the port:
Summary of Contents for IFS NS3550-24T/4S
Page 1: ...P N 1072569 REV 00 05 ISS 11OCT12 IFS NS3550 24T 4S User Manual ...
Page 37: ...User s Manual of NS3550 24T 4S 37 ...
Page 96: ...96 Figure 4 4 6 Port Mirror Configuration Page Screenshot ...
Page 127: ...User s Manual of NS3550 24T 4S 127 Figure 4 6 10 Port 1 Port 6 VLAN Configuration ...
Page 184: ...184 Figure 4 9 14 Voice VLAN Configuration Page Screenshot ...
Page 204: ...204 Figure 4 11 4 Network Access Server Configuration Page Screenshot ...
Page 234: ...234 Figure 4 12 1 Port Limit Control Configuration Overview Page Screenshot ...
Page 250: ...250 Click to undo any changes made locally and revert to previously saved values ...
Page 297: ...User s Manual of NS3550 24T 4S 297 ...
Page 388: ...388 Example Show RADIUS statistics SWITCH security aaa statistics ...
Page 410: ...410 Parameters vid VLAN ID 1 4095 Default Setting disable ...