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 Note |
If you try to set the maximum value to a number less than the number of secure addresses already configured on an interface, the command is rejected. |
The maximum number of secure MAC addresses that you can configure on a switch is set by the maximum number of available MAC addresses allowed in the system. This number is the total of available MAC addresses, including those used for other Layer 2 functions and any other secure MAC addresses configured on interfaces.
Port Security is not supported on EtherChanel interfaces.
Port Security is not supported on private VLAN ports.
Information About Port Security
You can use the port security feature to restrict input to an interface by limiting and identifying MAC addresses of the stations allowed to access the port. When you assign secure MAC addresses to a secure port, the port does not forward packets with source addresses outside the group of defined addresses. If you limit the number of secure MAC addresses to one and assign a single secure MAC address, the workstation attached to that port is assured the full bandwidth of the port.
If a port is configured as a secure port and the maximum number of secure MAC addresses is reached, when the MAC address of a station attempting to access the port is different from any of the identified secure MAC addresses, a security violation occurs. Also, if a station with a secure MAC address configured or learned on one secure port attempts to access another secure port, a violation is flagged.
The switch supports these types of secure MAC addresses:
Static secure MAC addresses—These are manually configured by using the switchport port-security mac-address mac-address interface configuration command, stored in the address table, and added to the switch running configuration.
Dynamic secure MAC addresses—These are dynamically configured, stored only in the address table, and removed when the switch restarts.
Sticky secure MAC addresses—These can be dynamically learned or manually configured, stored in the address table, and added to the running configuration. If these addresses are saved in the configuration file, when the switch restarts, the interface does not need to dynamically reconfigure them.
You can configure an interface to convert the dynamic MAC addresses to sticky secure MAC addresses and to add them to the running configuration by enabling sticky learning. The interface converts all the dynamic secure MAC addresses, including those that were dynamically learned before sticky learning was enabled, to sticky secure MAC addresses. All sticky secure MAC addresses are added to the running configuration.
The sticky secure MAC addresses do not automatically become part of the configuration file, which is the startup configuration used each time the switch restarts. If you save the sticky secure MAC addresses in the configuration file, when the switch restarts, the interface does not need to relearn these addresses. If you do not save the sticky secure addresses, they are lost.
If sticky learning is disabled, the sticky secure MAC addresses are converted to dynamic secure addresses and are removed from the running configuration.
It is a security violation when one of these situations occurs:
The maximum number of secure MAC addresses have been added to the address table, and a station whose MAC address is not in the address table attempts to access the interface.
An address learned or configured on one secure interface is seen on another secure interface in the same VLAN.
Running diagnostic tests with port security enabled.
You can configure the interface for one of three violation modes, based on the action to be taken if a violation occurs:
protect—when the number of secure MAC addresses reaches the maximum limit allowed on the port, packets with unknown source addresses are dropped until you remove a sufficient number of secure MAC addresses to drop below the maximum value or increase the number of maximum allowable addresses. You are not notified that a security violation has occurred.
Note |
We do not recommend configuring the protect violation mode on a trunk port. The protect mode disables learning when any VLAN reaches its maximum limit, even if the port has not reached its maximum limit. |
restrict—when the number of secure MAC addresses reaches the maximum limit allowed on the port, packets with unknown source addresses are dropped until you remove a sufficient number of secure MAC addresses to drop below the maximum value or increase the number of maximum allowable addresses. In this mode, you are notified that a security violation has occurred. An SNMP trap is sent, a syslog message is logged, and the violation counter increments.
shutdown—a port security violation causes the interface to become error-disabled and to shut down immediately, and the port LED turns off. When a secure port is in the error-disabled state, you can bring it out of this state by entering the errdisable recovery cause psecure-violation global configuration command, or you can manually re-enable it by entering the shutdown and no shut down interface configuration commands. This is the default mode.
shutdown vlan—Use to set the security violation mode per-VLAN. In this mode, the VLAN is error disabled instead of the entire port when a violation occurs
This table shows the violation mode and the actions taken when you configure an interface for port security.
|
Violation Mode |
Traffic is forwarded 1 |
Sends SNMP trap |
Sends syslog message |
Displays error message 2 |
Violation counter increments |
Shuts down port |
|---|---|---|---|---|---|---|
|
protect |
No |
No |
No |
No |
No |
No |
|
restrict |
No |
Yes |
Yes |
No |
Yes |
No |
|
shutdown |
No |
No |
No |
No |
Yes |
Yes |
|
shutdown vlan |
No |
No |
Yes |
No |
Yes |
No 3 |
You can use port security aging to set the aging time for all secure addresses on a port. Two types of aging are supported per port:
Absolute—The secure addresses on the port are deleted after the specified aging time.
Inactivity—The secure addresses on the port are deleted only if the secure addresses are inactive for the specified aging time.
When a switch joins a stack, the new switch will get the configured secure addresses. All dynamic secure addresses are downloaded by the new stack member from the other stack members.
When a switch (either the active switch or a stack member) leaves the stack, the remaining stack members are notified, and the secure MAC addresses configured or learned by that switch are deleted from the secure MAC address table.
|
Feature |
Default Setting |
|---|---|
|
Port security |
Disabled on a port. |
|
Sticky address learning |
Disabled. |
|
Maximum number of secure MAC addresses per port |
1. |
|
Violation mode |
Shutdown. The port shuts down when the maximum number of secure MAC addresses is exceeded. |
|
Port security aging |
Disabled. Aging time is 0. Static aging is disabled. Type is absolute. |
Port security can only be configured on static access ports or trunk ports. A secure port cannot be a dynamic access port.
A secure port cannot be a destination port for Switched Port Analyzer (SPAN).
Voice VLAN is only supported on access ports and not on trunk ports, even though the configuration is allowed.
When you enable port security on an interface that is also configured with a voice VLAN, set the maximum allowed secure addresses on the port to two. When the port is connected to a Cisco IP phone, the IP phone requires one MAC address. The Cisco IP phone address is learned on the voice VLAN, but is not learned on the access VLAN. If you connect a single PC to the Cisco IP phone, no additional MAC addresses are required. If you connect more than one PC to the Cisco IP phone, you must configure enough secure addresses to allow one for each PC and one for the phone.
When a trunk port configured with port security and assigned to an access VLAN for data traffic and to a voice VLAN for voice traffic, entering the switchport voice and switchport priority extend interface configuration commands has no effect.
When a connected device uses the same MAC address to request an IP address for the access VLAN and then an IP address for the voice VLAN, only the access VLAN is assigned an IP address.
When you enter a maximum secure address value for an interface, and the new value is greater than the previous value, the new value overwrites the previously configured value. If the new value is less than the previous value and the number of configured secure addresses on the interface exceeds the new value, the command is rejected.
The switch does not support port security aging of sticky secure MAC addresses.
This table summarizes port security compatibility with other port-based features.
|
Type of Port or Feature on Port |
Compatible with Port Security |
|---|---|
|
No |
|
|
Trunk port |
Yes |
|
Dynamic-access port 6 |
No |
|
Routed port |
No |
|
SPAN source port |
Yes |
|
SPAN destination port |
No |
|
EtherChannel |
No |
|
Tunneling port |
Yes |
|
Protected port |
Yes |
|
IEEE 802.1x port |
Yes |
|
Voice VLAN port 7 |
Yes |
|
IP source guard |
Yes |
|
Dynamic Address Resolution Protocol (ARP) inspection |
Yes |
|
Flex Links |
Yes |
How to Configure Port Security
This task restricts input to an interface by limiting and identifying MAC addresses of the stations allowed to access the port:
| Command or Action | Purpose | |||||
|---|---|---|---|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
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Step 2 |
configure terminal Example: |
Enters global configuration mode. |
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Step 3 |
interface interface-id Example: |
Specifies the interface to be configured, and enter interface configuration mode. |
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Step 4 |
switchport mode {access | trunk} Example: |
Sets the interface switchport mode as access or trunk; an interface in the default mode (dynamic auto) cannot be configured as a secure port. |
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|
Step 5 |
switchport voice vlan vlan-id Example: |
Enables voice VLAN on a port. vlan-id—Specifies the VLAN to be used for voice traffic. |
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|
Step 6 |
switchport port-security Example: |
Enable port security on the interface.
|
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|
Step 7 |
switchport port-security [maximum value [vlan {vlan-list | {access | voice}}]] Example: |
(Optional) Sets the maximum number of secure MAC addresses for the interface. The maximum number of secure MAC addresses that you can configure on a switch or switch stack is set by the maximum number of available MAC addresses allowed in the system. This number is the total of available MAC addresses, including those used for other Layer 2 functions and any other secure MAC addresses configured on interfaces. (Optional) vlan —sets a per-VLAN maximum value Enter one of these options after you enter the vlan keyword:
|
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|
Step 8 |
switchport port-security violation {protect | restrict | shutdown | shutdown vlan} Example: |
(Optional) Sets the violation mode, the action to be taken when a security violation is detected, as one of these:
|
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|
Step 9 |
switchport port-security [mac-address mac-address [vlan {vlan-id | {access | voice}}] Example: |
(Optional) Enters a secure MAC address for the interface. You can use this command to enter the maximum number of secure MAC addresses. If you configure fewer secure MAC addresses than the maximum, the remaining MAC addresses are dynamically learned.
(Optional) vlan —sets a per-VLAN maximum value. Enter one of these options after you enter the vlan keyword:
|
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|
Step 10 |
switchport port-security mac-address sticky Example: |
(Optional) Enables sticky learning on the interface. |
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|
Step 11 |
switchport port-security mac-address sticky [mac-address | vlan {vlan-id | {access | voice}}] Example: |
(Optional) Enters a sticky secure MAC address, repeating the command as many times as necessary. If you configure fewer secure MAC addresses than the maximum, the remaining MAC addresses are dynamically learned, are converted to sticky secure MAC addresses, and are added to the running configuration.
(Optional) vlan —sets a per-VLAN maximum value. Enter one of these options after you enter the vlan keyword:
|
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|
Step 12 |
end Example: |
Returns to privileged EXEC mode. |
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Step 13 |
show port-security Example: |
Verifies your entries. |
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Step 14 |
show running-config Example: |
Verifies your entries. |
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|
Step 15 |
copy running-config startup-config Example: |
(Optional) Saves your entries in the configuration file. |
Use this feature to remove and add devices on a secure port without manually deleting the existing secure MAC addresses and to still limit the number of secure addresses on a port. You can enable or disable the aging of secure addresses on a per-port basis.
| Command or Action | Purpose | |||
|---|---|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
||
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
||
|
Step 3 |
interface interface-id Example: |
Specifies the interface to be configured, and enter interface configuration mode. |
||
|
Step 4 |
switchport port-security aging {static | time time | type {absolute | inactivity}} Example: |
Enables or disable static aging for the secure port, or set the aging time or type.
Enter static to enable aging for statically configured secure addresses on this port. For time , specifies the aging time for this port. The valid range is from 0 to 1440 minutes. For type , select one of these keywords:
|
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|
Step 5 |
end Example: |
Returns to privileged EXEC mode. |
||
|
Step 6 |
show port-security [interface interface-id] [address] Example: |
Verifies your entries. |
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|
Step 7 |
show running-config Example: |
Verifies your entries. |
||
|
Step 8 |
copy running-config startup-config Example: |
(Optional) Saves your entries in the configuration file. |
This example shows how to enable port security on a port and to set the maximum number of secure addresses to 50. The violation mode is the default, no static secure MAC addresses are configured, and sticky learning is enabled.
Device(config)# interface gigabitethernet1/0/1
Device(config-if)# switchport mode access
Device(config-if)# switchport port-security
Device(config-if)# switchport port-security maximum 50
Device(config-if)# switchport port-security mac-address sticky
This example shows how to configure a static secure MAC address on VLAN 3 on a port:
Device(config)# interface gigabitethernet1/0/2
Device(config-if)# switchport mode trunk
Device(config-if)# switchport port-security
Device(config-if)# switchport port-security mac-address 0000.0200.0004 vlan 3
This example shows how to enable sticky port security on a port, to manually configure MAC addresses for data VLAN and voice VLAN, and to set the total maximum number of secure addresses to 20 (10 for data VLAN and 10 for voice VLAN).
Device(config)# interface tengigabitethernet1/0/1
Device(config-if)# switchport access vlan 21
Device(config-if)# switchport mode access
Device(config-if)# switchport voice vlan 22
Device(config-if)# switchport port-security
Device(config-if)# switchport port-security maximum 20
Device(config-if)# switchport port-security violation restrict
Device(config-if)# switchport port-security mac-address sticky
Device(config-if)# switchport port-security mac-address sticky 0000.0000.0002
Device(config-if)# switchport port-security mac-address 0000.0000.0003
Device(config-if)# switchport port-security mac-address sticky 0000.0000.0001 vlan voice
Device(config-if)# switchport port-security mac-address 0000.0000.0004 vlan voice
Device(config-if)# switchport port-security maximum 10 vlan access
Device(config-if)# switchport port-security maximum 10 vlan voice
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