- Preface
- New and Changed Information
- Overview
- Configuring Authentication, Authorization, and Accounting
- Configuring RADIUS
- Configuring TACACS+
- Configuring SSH and Telnet
- Configuring Cisco TrustSec
- Configuring Access Control Lists
- Configuring Port Security
- Configuring DHCP Snooping
- Configuring Dynamic ARP Inspection
- Configuring IP Source Guard
- Configuring Control Plane Policing
- Index
- Information About Port Security
- Licensing Requirements for Port Security
- Prerequisites for Port Security
- Guidelines and Limitations for Port Security
- Guidelines and Limitations for Port Security on vPCs
- Configuring Port Security
- Enabling or Disabling Port Security Globally
- Enabling or Disabling Port Security on a Layer 2 Interface
- Enabling or Disabling Sticky MAC Address Learning
- Adding a Static Secure MAC Address on an Interface
- Removing a Static Secure MAC Address on an Interface
- Removing a Dynamic Secure MAC Address
- Configuring a Maximum Number of MAC Addresses
- Configuring an Address Aging Type and Time
- Configuring a Security Violation Action
- Verifying the Port Security Configuration
- Displaying Secure MAC Addresses
- Configuration Example for Port Security
- Configuration Example of Port Security in a vPC Domain
- Default Settings for Port Security
- Additional References for Port Security
- Feature History for Port Security
Configuring Port Security
This chapter includes the following sections:
- Information About Port Security
- Licensing Requirements for Port Security
- Prerequisites for Port Security
- Guidelines and Limitations for Port Security
- Guidelines and Limitations for Port Security on vPCs
- Configuring Port Security
- Verifying the Port Security Configuration
- Displaying Secure MAC Addresses
- Configuration Example for Port Security
- Configuration Example of Port Security in a vPC Domain
- Default Settings for Port Security
- Additional References for Port Security
- Feature History for Port Security
Information About Port Security
Port security allows you to configure Layer 2 physical interfaces, Layer 2 port-channel interfaces, and virtual port channels (vPCs) to allow inbound traffic from only a restricted set of MAC addresses. The MAC addresses in the restricted set are called secure MAC addresses. In addition, the device does not allow traffic from these MAC addresses on another interface within the same VLAN. The number of MAC addresses that the device can secure is configurable per interface.
 Note | Unless otherwise specified, the term interface refers to physical interfaces, port-channel interfaces, and vPCs; likewise, the term Layer 2 interface refers to both Layer 2 physical interfaces and Layer 2 port-channel interfaces. |
- Secure MAC Address Learning
- Dynamic Address Aging
- Secure MAC Address Maximums
- Security Violations and Actions
- Port Type Changes
Secure MAC Address Learning
The process of securing a MAC address is called learning. A MAC address can be a secure MAC address on one interface only. For each interface that you enable port security on, the device can learn a limited number of MAC addresses by the static, dynamic, or sticky methods. The way that the device stores secure MAC addresses varies depending upon how the device learned the secure MAC address.
Note | All learned MAC addresses are synchronized between vPC peers. |
Static Method
The static learning method allows you to manually add or remove secure MAC addresses to the running configuration of an interface. If you copy the running configuration to the startup configuration, static secure MAC addresses are unaffected if the device restarts.
A static secure MAC address entry remains in the configuration of an interface until one of the following events occurs:
-
You explicitly remove the address from the configuration.
-
You configure the interface to act as a Layer 3 interface.
Adding secure addresses by the static method is not affected by whether dynamic or sticky address learning is enabled.
Dynamic Method
By default, when you enable port security on an interface, you enable the dynamic learning method. With this method, the device secures MAC addresses as ingress traffic passes through the interface. If the address is not yet secured and the device has not reached any applicable maximum, it secures the address and allows the traffic.
The device stores dynamic secure MAC addresses in memory. A dynamic secure MAC address entry remains in the configuration of an interface until one of the following events occurs:
Sticky Method
If you enable the sticky method, the device secures MAC addresses in the same manner as dynamic address learning, but the device stores addresses learned by this method in nonvolatile RAM (NVRAM). As a result, addresses learned by the sticky method persist through a device restart. Sticky secure MAC addresses do not appear in the running configuration of an interface.
Dynamic and sticky address learning are mutually exclusive. When you enable sticky learning on an interface, the device stops dynamic learning and performs sticky learning instead. If you disable sticky learning, the device resumes dynamic learning.
A sticky secure MAC address entry remains in the configuration of an interface until one of the following events occurs:
Dynamic Address Aging
The device ages MAC addresses learned by the dynamic method and drops them after the age limit is reached. You can configure the age limit on each interface. The range is from 0 to 1440 minutes, where 0 disables aging.
In vPC domains, dynamic MAC addresses are dropped only after the age limit is reached on both vPC peers.
The method that the device uses to determine that the MAC address age is also configurable. The two methods of determining address age are as follows:
- Inactivity
-
The length of time after the device last received a packet from the address on the applicable interface.
- Absolute
-
The length of time after the device learned the address. This is the default aging method; however, the default aging time is 0 minutes, which disables aging.
Note | If the absolute method is used to age out a MAC address, then depending on the traffic rate, few packets may drop each time a MAC address is aged out and relearned. To avoid this use inactivity timeout. |
Secure MAC Address Maximums
By default, an interface can have only one secure MAC address. You can configure the maximum number of MAC addresses permitted per interface or per VLAN on an interface. Maximums apply to secure MAC addresses learned by any method: dynamic, sticky, or static.
Note | In vPC domains, the configuration on the primary vPC takes effect. |
 Tip | To ensure that an attached device has the full bandwidth of the port, set the maximum number of addresses to one and configure the MAC address of the attached device. |
The following three limits can determine how many secure MAC addresses are permitted on an interface:
- Device maximum
The device has a nonconfigurable limit of 8192 secure MAC addresses. If learning a new address would violate the device maximum, the device does not permit the new address to be learned, even if the interface or VLAN maximum has not been reached.
- Interface maximum
You can configure a maximum number of 1025 secure MAC addresses for each interface protected by port security. The default interface maximum is one address. Interface maximums cannot exceed the device maximum.
In vPC domains, you set the maximum number of secure MAC addresses on the primary vPC switch. The primary vPC switch does the count validation, even if a maximum number of secure MAC addresses is set on the secondary switch.
- VLAN maximum
You can configure the maximum number of secure MAC addresses per VLAN for each interface protected by port security. A VLAN maximum cannot exceed the configured interface maximum. VLAN maximums are useful only for trunk ports. There are no default VLAN maximums.
You can configure VLAN and interface maximums per interface, as needed; however, when the new limit is less than the applicable number of secure addresses, you must reduce the number of secure MAC addresses first.
Security Violations and Actions
Port security triggers security violations when either of the two following events occur:
- MAX Count Violation
Ingress traffic arrives at an interface from a nonsecure MAC address and learning the address would exceed the applicable maximum number of secure MAC addresses. The blocked entry is added to the Forwarding Module (FWM) of the Cisco Nexus switch.
When an interface has both a VLAN maximum and an interface maximum configured, a violation occurs when either maximum is exceeded. For example, consider the following on a single interface configured with port security: The device detects a violation when any of the following occurs: - MAC Move Violation
Ingress traffic from a secure MAC address arrives at a different interface in the same VLAN as the interface on which the address is secured. The blocked entry is added as a drop entry in the Port Security table.
When a security violation occurs, the device increments the security violation counter for the interface and takes the action specified by the port security configuration of the interface. If a violation occurs because ingress traffic from a secure MAC address arrives at a different interface than the interface on which the address is secure, the device applies the action on the interface that received the traffic.
The possible actions that the device can take are as follows:
- Shutdown
-
Shuts down the interface that received the packet triggering the violation. The interface is error disabled. This action is the default. After you reenable the interface, it retains its port security configuration, including its secure MAC addresses.
You can use the errdisable global configuration command to configure the device to reenable the interface automatically if a shutdown occurs, or you can manually reenable the interface by entering the shutdown and no shut down interface configuration commands.
- Restrict
-
Drops ingress traffic from any nonsecure MAC addresses and adds the MAC address as a blocked MAC entry in the port security table..
NoteIn vPC domains, blocked MAC addresses added to the port security table due to violations occuring in the Restrict mode are not synchronized across vPC peers.
The device keeps a count of the number of dropped packets, which is called the security violation count. Address learning continues until the maximum security violations have occurred on the interface. Traffic from addresses learned after the first security violation is dropped.
- Protect
-
Prevents further violations from occurring. The address that triggered the security violation is learned but any traffic from the address is dropped. Further address learning stops.
Note | In vPCs, the violation action configured on the primary vPC switch takes affect. So, whenever a security violation is triggered, the security action defined on the primary vPC switch occurs. |
After the maximum number of MAX move violations (10) is reached, the interface is shut down and placed in the errdisabled state.
Port Type Changes
When you have configured port security on a Layer 2 interface and you change the port type of the interface, the device behaves as follows:
- Access port to trunk port
When you change a Layer 2 interface from an access port to a trunk port, the device drops all secure addresses learned by the dynamic method. The device moves the addresses learned by the static or sticky method to the native trunk VLAN.
- Trunk port to access port
When you change a Layer 2 interface from a trunk port to an access port, the device drops all secure addresses learned by the dynamic method. It also moves all addresses learned by the sticky method on the native trunk VLAN to the access VLAN. The device drops secure addresses learned by the sticky method if they are not on the native trunk VLAN.
- Switched port to routed port
When you change an interface from a Layer 2 interface to a Layer 3 interface, the device disables port security on the interface and discards all port security configuration for the interface. The device also discards all secure MAC addresses for the interface, regardless of the method used to learn the address.
- Routed port to switched port
When you change an interface from a Layer 3 interface to a Layer 2 interface, the device has no port security configuration for the interface.
Licensing Requirements for Port Security
|
Product |
License Requirement |
|---|---|
|
Cisco NX-OS |
Port security requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS device images and is provided at no extra charge to you. For an explanation of the Cisco NX-OS licensing scheme, see the License and Copyright Information for Cisco NX-OS Software available at the following URL: http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_0/nx-os/license_agreement/nx-ossw_lisns.html. |
Prerequisites for Port Security
Port security has the following prerequisites:
-
You must globally enable port security for the device that you want to protect with port security.
In a vPC domain, you must enable port security globally on both vPC peers and on both vPC interfaces on the vPC peers. We recommend that you use the config sync command to ensure that the configuration is consistent on both vPC peers.
Guidelines and Limitations for Port Security
When configuring port security, follow these guidelines:
-
Port security is supported on PVLAN ports.
-
Port security does not support switched port analyzer (SPAN) destination ports.
-
Port security does not depend upon other features.
Port security is not supported on vPC peer links.
Port security is not supported on Network Interface (NIF) port, Flex Link ports, or vEthernet interfaces.
Guidelines and Limitations for Port Security on vPCs
In addition to the guidelines and limitations for port security, there are additional guidelines and limitations for port security on vPCs. When configuring port security on vPCs, follow these guidelines:
You must enabled port security globally on both vPC peers in a vPC domain.
You must enable port security on the vPC interfaces of both vPC peers.
You must configure a static secure MAC address on the primary vPC peer. This MAC address is synchronized with the secondary vPC peer. Do not configure a static secure MAC address on the secondary peer. This MAC address appears in the secondary vPC configuration, but does not take affect.
All learned MAC addresses are synchronized between vPC peers.
Both vPC peers can be configured with either the dynamic or sticky MAC address learning method. However, we recommend that both vPC peers be configured for the same method.
Dynamic MAC addresses are dropped only after the age limit is reached on both vPC peers.
You set the maximum number of secure MAC addresses on the primary vPC switch. The primary vPC switch does the count validation, even if a maximum number of secure MAC addresses is set on the secondary switch.
You configure the violation action on the primary vPC. So, whenever a security violation is triggered, the security action defined on the primary vPC switch occurs.
Port security is enabled on a vPC interface when the port security feature is enabled on both vPC peers and port security is enabled on both vPC interfaces of the vPC peers. You can use the config sync command to verify that the configuration is correct.
While a switch undergoes an in-service software upgrade (ISSU), port security operations are stopped on its peer switch. The peer switch does not learn any new MAC addresses, and MAC moves occurring during this operation are ignored. When the ISSU is complete, the peer switch is notified and normal port security functionality resumes.
ISSU to higher versions is supported; however ISSU to lower versions is not supported.
Configuring Port Security
- Enabling or Disabling Port Security Globally
- Enabling or Disabling Port Security on a Layer 2 Interface
- Enabling or Disabling Sticky MAC Address Learning
- Adding a Static Secure MAC Address on an Interface
- Removing a Static Secure MAC Address on an Interface
- Removing a Dynamic Secure MAC Address
- Configuring a Maximum Number of MAC Addresses
- Configuring an Address Aging Type and Time
- Configuring a Security Violation Action
Enabling or Disabling Port Security Globally
You can enable or disable port security globally on a device. By default, port security is disabled globally.
When you disable port security, all port security configuration on the interface is ineffective. When you disable port security globally, all port security configuration is lost.
Note | To enable or disable port security in a vPC domain, you must enable or disable port security globally on both vPC peers. |
1.
configure terminal
2.
[no] feature port-security
3.
show
port-security
4.
(Optional)
copy running-config startup-config
5. If you are configuring port security for a vPC domain, repeat steps 1 through 4 on the vPC peer to enable port security globally.
DETAILED STEPS
Enabling or Disabling Port Security on a Layer 2 Interface
You can enable or disable port security on a Layer 2 interface. By default, port security is disabled on all interfaces.
When you disable port security on an interface, all switchport port security configuration for the interface is lost.
You must have enabled port security globally.
If you are setting up port security in a vPC domain, you must have enabled port security globally on both vPC peers.
If a Layer 2 Ethernet interface is a member of a port-channel interface, you cannot enable or disable port security on the Layer 2 Ethernet interface.
If any member port of a secure Layer 2 port-channel interface has port security enabled, you cannot disable port security for the port-channel interface unless you first remove all secure member ports from the port-channel interface.
1.
configure terminal
2.
Enter one of the following commands:
3.
switchport
4.
[no] switchport port-security
5.
show running-config port-security
6.
(Optional)
copy running-config startup-config
7. If you are configuring port security for a vPC domain, repeat steps 1 through 6 to on the vPC peer to enable port security on its vPC interface.
DETAILED STEPS
Enabling or Disabling Sticky MAC Address Learning
You can disable or enable sticky MAC address learning on an interface. If you disable sticky learning, the device returns to dynamic MAC address learning on the interface, which is the default learning method.
By default, sticky MAC address learning is disabled.
You must have enabled port security globally.
1.
configure terminal
2.
Enter one of the following commands:
3.
switchport
4.
[no] switchport port-security mac-address sticky
5.
show running-config port-security
6.
(Optional)
copy running-config startup-config
DETAILED STEPS
Adding a Static Secure MAC Address on an Interface
You can add a static secure MAC address on a Layer 2 interface.
Note | If the MAC address is a secure MAC address on any interface, you cannot add it as a static secure MAC address to another interface until you remove it from the interface on which it is already a secure MAC address. |
By default, no static secure MAC addresses are configured on an interface.
You must have enabled port security globally.
Verify that the interface maximum has not been reached for secure MAC addresses. If needed, you can remove a secure MAC address or you can change the maximum number of addresses on the interface.
1.
configure terminal
2.
Enter one of the following commands:
3.
[no] switchport port-security mac-address
address [vlan
vlan-ID]
4.
show running-config port-security
5.
(Optional)
copy running-config startup-config
DETAILED STEPS
Removing a Static Secure MAC Address on an Interface
You can remove a static secure MAC address on a Layer 2 interface.
1.
configure terminal
2.
Enter one of the following commands:
3.
no
switchport port-security mac-address
address
4.
show running-config port-security
5.
(Optional)
copy running-config startup-config
DETAILED STEPS
Removing a Dynamic Secure MAC Address
You can remove dynamically learned, secure MAC addresses.
You must have enabled port security globally.
1.
configure terminal
2.
clear port-security dynamic {interface ethernet
slot/port | address
address} [vlan
vlan-ID]
3.
show port-security address
4.
(Optional)
copy running-config startup-config
DETAILED STEPS
Configuring a Maximum Number of MAC Addresses
You can configure the maximum number of MAC addresses that can be learned or statically configured on a Layer 2 interface. You can also configure a maximum number of MAC addresses per VLAN on a Layer 2 interface. The largest maximum number of addresses that you can configure on an interface is 1025 addresses. The system maximum number of address is 8192.
By default, an interface has a maximum of one secure MAC address. VLANs have no default maximum number of secure MAC addresses.
Note | When you specify a maximum number of addresses that is less than the number of addresses already learned or statically configured on the interface, the device rejects the command. To remove all addresses learned by the dynamic method, use the shutdown and no shutdown commands to restart the interface. |
You must have enabled port security globally.
1.
configure terminal
2.
Enter one of the following commands:
3.
[no] switchport port-security maximum
number [vlan
vlan-ID]
4.
show running-config port-security
5.
(Optional)
copy running-config startup-config
DETAILED STEPS
Configuring an Address Aging Type and Time
You can configure the MAC address aging type and the length of time that the device uses to determine when MAC addresses learned by the dynamic method have reached their age limit.
Absolute aging is the default aging type.
By default, the aging time is 0 minutes, which disables aging.
You must have enabled port security globally.
1.
configure terminal
2.
Enter one of the following commands:
3.
[no] switchport port-security aging type {absolute | inactivity}
4.
[no] switchport port-security aging time
minutes
5.
show running-config port-security
6.
(Optional)
copy running-config startup-config
DETAILED STEPS
Configuring a Security Violation Action
You can configure the action that the device takes if a security violation occurs. The violation action is configurable on each interface that you enable with port security.
The default security action is to shut down the port on which the security violation occurs.
You must have enabled port security globally.
1.
configure terminal
2.
Enter one of the following commands:
3.
[no] switchport port-security
violation {protect | restrict | shutdown}
4.
show running-config port-security
5.
(Optional)
copy running-config startup-config
DETAILED STEPS
Verifying the Port Security Configuration
|
Command |
Purpose |
|---|---|
|
show running-config port-security |
Displays the port security configuration. |
|
show port-security |
Displays the port security status of the device. |
|
show port-security interface |
Displays the port security status of a specific interface. |
|
show port-security address |
Displays secure MAC addresses. |
|
show running-config interface |
Displays the interfaces that are in the running-configuration. |
|
show mac address-table |
Displays the contents of the MAC address table. |
|
show system internal port-security info global |
Displays the port security settings of the device. |
Displaying Secure MAC Addresses
Use the show port-security address command to display secure MAC addresses. For detailed information about the fields in the output from this command, see the Security Command Reference for your platform.
Configuration Example for Port Security
The following example shows a port security configuration for the Ethernet 2/1 interface with VLAN and interface maximums for secure addresses. In this example, the interface is a trunk port. Additionally, the violation action is set to Restrict.
feature port-security interface Ethernet 2/1 switchport switchport port-security switchport port-security maximum 10 switchport port-security maximum 7 vlan 10 switchport port-security maximum 3 vlan 20 switchport port-security violation restrict
Configuration Example of Port Security in a vPC Domain
The following example shows how to enable and configure port security on vPC peers in a vPC domain. The first switch is the primary vPC peer and the second switch is the secondary vPC peer. It is assumed that domain 103 has already been created.
primary_switch(config)# feature port-security primary_switch(config-if)# int e1/1 primary_switch(config-if)# switchport port-security primary_switch(config-if)# switchport port-security max 1025 primary_switch(config-if)# switchport port-security violation restrict primary_switch(config-if)# switchport port-security aging time 4 primary_switch(config-if)# switchport port-security aging type absolute primary_switch(config-if)# switchport port-security mac sticky primary_switch(config-if)# switchport port-security mac-address 0.0.1 vlan 101 primary_switch(config-if)# switchport port-security mac-address 0.0.2 vlan 101 primary_switch(config-if)# copy running-config startup-config secondary_switch(config)# int e103/1/1 secondary_switch(config-if)# switchport port-security secondary_switch(config-if)# copy running-config startup-config
Default Settings for Port Security
|
Parameters |
Default |
|---|---|
|
Port security enablement globally |
Disabled |
|
Port security enablement per interface |
Disabled |
|
MAC address learning method |
Dynamic |
|
Interface maximum number of secure MAC addresses |
1 |
|
Security violation action |
Shutdown |
Additional References for Port Security
Related Documents
|
Related Topic |
Document Title |
|---|---|
|
Layer 2 switching |
|
|
Port security commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples |
Standards
|
Standards |
Title |
|---|---|
|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
— |
MIBs
Cisco NX-OS provides read-only SNMP support for port security.
|
MIBs |
MIBs Link |
||
|---|---|---|---|
|
To locate and download MIBs, go to the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml |
Feature History for Port Security
Feature Name |
Releases |
Feature Information |
|---|---|---|
Port security |
5.1(3)N1(1) |
Feature introduced in this release. |
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