Usage Guidelines

This command does not require a license.

Usage Guidelines

You can use this command on the following interfaces:

• Layer 2 interface (Ethernet interface, EtherChannel interface, subinterface)
• Layer 3 interface

Note	Use the no switchport command to configure an interface as a Layer 3 interface.

• Layer 3 subinterface
• Management interface
• Virtual Ethernet interface

Usage Guidelines

Use this command to enable preprovisioning of features or interfaces of a module on a slot in a chassis. Preprovisioning allows you configure features or interfaces (Ethernet, Fibre Channel) on modules before the modules are inserted in the switch chassis.

Usage Guidelines

The snmp-server enable traps command enables both traps and informs, depending on the configured notification host receivers.

Usage Guidelines

A source port (also called a monitored port ) is a switched port that you monitor for network traffic analysis. In a single local SPAN session, you can monitor source port traffic such as received (Rx), transmitted (Tx), or bidirectional (both).

A source port can be an Ethernet port, port channel, SAN port channel, VLAN, or a VSAN port. It cannot be a destination port.

Note	For Cisco NX-OS Release 4.2(1)N2(1) and earlier, the Cisco Nexus 5010 Switch and the Cisco Nexus 5020 Switch supports a maximum of two egress SPAN source ports.

Beginning with Cisco NX-OS Release 5.0(2)N2(1):

• There is no limit to the number of egress SPAN source ports.
• SAN Port Channel interfaces can be configured as ingress or egress source ports.
• The limit on the number of egress (TX) sources in a monitor session has been lifted.
• Port-channel interfaces can be configured as egress sources.

For ERSPAN, if you do not specify both , rx , or tx , the source traffic is analyzed for both directions.

Usage Guidelines

Entering the spanning-tree bpdufilter enable command to enable BPDU Filtering overrides the spanning tree edge port configuration. That port then returns to the normal spanning tree port type and moves through the normal spanning tree transitions.

Caution

Be careful when you enter the spanning-tree bpdufilter enable command on specified interfaces. Explicitly configuring BPDU Filtering on a port this is not connected to a host can cause a bridging loop because the port will ignore any BPDU that it receives, and the port moves to the STP forwarding state.

Use the spanning-tree port type edge bpdufilter default command to enable BPDU Filtering on all spanning tree edge ports.

Usage Guidelines

BPDU Guard prevents a port from receiving BPDUs. If the port still receives a BPDU, it is put in the error-disabled state as a protective measure.

Caution

Be careful when using this command. You should use this command only with interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data-packet loop and disrupt the switch and network operation.

When you enable this BPDU Guard command globally, the command applies only to spanning tree edge ports. See the spanning-tree port type edge bpdufilter default command for more information on the global command for BPDU Guard. However, when you enable this feature on an interface, it applies to that interface regardless of the spanning tree port type.

This command has three states:

• spanning-tree bpduguard enable — Unconditionally enables BPDU Guard on the interface.
• spanning-tree bpduguard disable — Unconditionally disables BPDU Guard on the interface.
• no spanning-tree bpduguard —E nables BPDU Guard on the interface if it is an operational spanning tree edge port and if the spanning-tree port type edge bpdufilter default command is configured.

Typically, this feature is used in a service-provider environment where the network administrator wants to prevent an access port from participating in the spanning tree.

Usage Guidelines

You can use Bridge Assurance to protect against certain problems that can cause bridging loops in the network.

Note	Bridge Assurance is supported only by Rapid per VLAN Spanning Tree Plus (Rapid PVST+) and Multiple Spanning Tree (MST). Legacy 802.1D spanning tree does not support Bridge Assurance.

Bridge Assurance is enabled by default and can only be disabled globally.

Bridge Assurance is enabled globally by default but is disabled on an interface by default. You can enable Bridge Assurance on an interface by using the spanning-tree port type network command.

For more information on Bridge Assurance, see the Cisco Nexus 5000 Series NX-OS Layer 2 Switching Configuration Guide .

This command does not require a license.

Usage Guidelines

The STP port path cost default value is determined from the media speed and path cost calculation method of a LAN interface (see the table below on Default Port Cost). See the spanning-tree pathcost method command for information on setting the path cost calculation method for Rapid per VLAN Spanning Tree Plus (Rapid PVST+).

When you configure the value , higher values will indicate higher costs.

On access ports, assign the port cost by port. On trunk ports, assign the port cost by VLAN; you can configure all the VLANs on a trunk port as the same port cost.

The EtherChannel bundle is considered as a single port. The port cost is the aggregation of all the configured port costs assigned to that channel.

Note	Use this command to set the port cost for Rapid PVST+. Use the spanning-tree mst cost command to set the port cost for MST.

Usage Guidelines

This command does not require a license.

Usage Guidelines

You cannot enable Loop Guard if Root Guard is enabled, although the switch accepts the command to enable Loop Guard on spanning tree edge ports.

Usage Guidelines

Fast transition (specified in IEEE 802.1w) functions only on point-to-point links between two bridges.

By default, the switch derives the link type of a port from the duplex mode. A full-duplex port is considered as a point-to-point link while a half-duplex configuration is assumed to be on a shared link.

Note	On a Cisco Nexus 5000 Series switch, port duplex is not configurable.

Usage Guidelines

Loop Guard provides additional security in the bridge network. Loop Guard prevents alternate or root ports from becoming the designated port because of a failure that could lead to a unidirectional link.

Loop Guard operates only on ports that are considered point-to-point links by the spanning tree, and it does not run on spanning tree edge ports.

Entering the spanning-tree guard loop command for the specified interface overrides this global Loop Guard command.

Usage Guidelines

You cannot simultaneously run MST and Rapid PVST+ on the switch.

Caution

Be careful when using the spanning-tree mode command to switch between Rapid PVST+ and MST modes. When you enter the command, all STP instances are stopped for the previous mode and are restarted in the new mode. Using this command may cause the user traffic to be disrupted.

Usage Guidelines

The MST configuration consists of three main parameters:

• Instance VLAN mapping—See the instance vlan command.
• Region name—See the name (MST configuration) command.
• Configuration revision number—See the revision command.

The abort and exit commands allow you to exit MST configuration mode. The difference between the two commands depends on whether you want to save your changes or not:

• The exit command commits all the changes before leaving MST configuration mode.
• The abort command leaves MST configuration mode without committing any changes.

If you do not map secondary VLANs to the same instance as the associated primary VLAN, when you exit MST configuration mode, the following warning message is displayed:

These secondary vlans are not mapped to the same instance as their primary:
-> 3

See the switchport mode private-vlan host command to fix this problem.

Changing an MST configuration mode parameter can cause connectivity loss. To reduce service disruptions, when you enter MST configuration mode, make changes to a copy of the current MST configuration. When you are done editing the configuration, you can apply all the changes at once by using the exit keyword.

In the unlikely event that two administrators commit a new configuration at exactly the same time, this warning message is displayed:

% MST CFG:Configuration change lost because of concurrent access

Usage Guidelines

The port cost depends on the port speed; the faster interface speeds indicate smaller costs. MST always uses long path costs.

Higher cost values indicate higher costs. When entering the cost, do not include a comma in the entry; for example, enter 1000, not 1,000.

The EtherChannel bundle is considered as a single port. The port cost is the aggregation of all the configured port costs assigned to that channel.

Usage Guidelines

If you do not specify the hello-time value, the value is calculated from the network diameter.

Usage Guidelines

This parameter is used only by Instance 0 or the IST.

Usage Guidelines

Higher port-priority priority values indicate smaller priorities.

The priority values are 0, 32, 64, 96, 128, 160, 192, and 224. All other values are rejected.

Usage Guidelines

This command does not require a license.

Usage Guidelines

You can set the bridge priority in increments of 4096 only. When you set the priority, valid values are 0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440.

You can set the priority-value argument to 0 to make the switch root.

You can enter the instance-id argument as a single instance or a range of instances, for example, 0-3,5,7-9.

Usage Guidelines

You can enter the instance-id argument as a single instance or a range of instances, for example, 0-3,5,7-9.

If you do not specify the hello-time argument, the argument is calculated from the network diameter. You must first specify the diameter dia keyword and argument before you can specify the hello-time hello-time keyword and argument.

Usage Guidelines

MST interoperates with Rapid PVST+ with no need for user configuration. The PVST+ simulation feature enables this seamless interoperability. However, you may want to control the connection between MST and Rapid PVST+ to protect against accidentally connecting an MST-enabled port to a Rapid PVST+-enabled port.

When you use the spanning-tree mst simulate pvst disable command, specified MST interfaces that receive a Rapid PVST+ (SSTP) bridge protocol data unit (BPDU) move into the STP blocking state. Those interfaces remain in the inconsistent state until the port stops receiving Rapid PVST+ BPDUs, and then the port resumes the normal STP transition process.

Note	To block automatic MST and Rapid PVST+ interoperability for the entire switch, use no spanning-tree mst simulate pvst global command.

This command is useful when you want to prevent accidental connection with a device running Rapid PVST+.

To reenable seamless operation between MST and Rapid PVST+ on specific interfaces, use the spanning-tree mst simulate pvst command.

Usage Guidelines

MST does not require user configuration to interoperate with Rapid PVST+. The PVST+ simulation feature enables this seamless interoperability. However, you may want to control the connection between MST and Rapid PVST+ to protect against accidentally connecting an MST-enabled port to a Rapid PVST+-enabled port.

When you use the no spanning-tree mst simulate pvst global command, the switch running in MST mode moves all interfaces that receive a Rapid PVST+ (SSTP) bridge protocol data unit (BPDU) into the Spanning Tree Protocol (STP) blocking state. Those interfaces remain in the inconsistent state until the port stops receiving Rapid PVST+ BPDUs, and then the port resumes the normal STP transition process.

You can also use this command from the interface mode, and the configuration applies to the entire switch.

Note	To block automatic MST and Rapid PVST+ interoperability for specific interfaces, see the spanning-tree mst simulate pvst command.

This command is useful when you want to prevent accidental connection with a device not running MST.

To return the switch to seamless operation between MST and Rapid PVST+, use the spanning-tree mst simulate pvst global command.

Usage Guidelines

The long path-cost calculation method uses all 32 bits for path-cost calculations and yields valued in the range of 2 through 2,00,000,000.

The short path-cost calculation method (16 bits) yields values in the range of 1 through 65535.

Note	This command applies only to the Rapid per VLAN Spanning Tree Plus (Rapid PVST+) spanning tree mode, which is the default mode. When you are using Multiple Spanning Tree (MST) spanning tree mode, the switch uses only the long method for calculating path cost; this is not user-configurable for MST.

Usage Guidelines

You can also use this command to configure a port in trunk mode as a spanning tree edge port.

Caution

You should use this command only with interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data-packet loop and disrupt the switch and network operation.

When a linkup occurs, spanning tree edge ports are moved directly to the spanning tree forwarding state without waiting for the standard forward-time delay.

Note	This is the same functionality that was previously provided by the Cisco-proprietary PortFast feature.

When you use this command, the system returns a message similar to the following:

Warning: portfast should only be enabled on ports connected to a single
 host. Connecting hubs, concentrators, switches, bridges, etc... to this
 interface when portfast is enabled, can cause temporary bridging loops.
 Use with CAUTION

When you use this command without the trunk keyword, the system returns an additional message similar to the following:

%Portfast has been configured on Ethernet1/40 but will only
 have effect when the interface is in a non-trunking mode.

To configure trunk interfaces as spanning tree edge ports, use the spanning-tree port type trunk command. To remove the spanning tree edge port type setting, use the no spanning-tree port type normal command.

The default spanning tree port type is normal.

Usage Guidelines

To enable BPDU Guard by default, you must do the following:

• Configure the interface as spanning tree edge ports by entering the spanning-tree port type edge or the spanning-tree port type edge default command.
• Enable BPDU Guard.

Use this command to enable BPDU Guard globally on all spanning tree edge ports. BPDU Guard disables a port if it receives a BPDU.

Global BPDU Guard is applied only on spanning tree edge ports.

You can also enable BPDU Guard per interface; see the spanning-tree bpduguard command for more information.

Note	We recommend that you enable BPDU Guard on all spanning tree edge ports.

Usage Guidelines

To enable BPDU Filtering by default, you must do the following:

• Configure the interface as a spanning tree edge port, using the spanning-tree port type edge or the spanning-tree port type edge default command.
• Enable BPDU Filtering.

Use this command to enable BPDU Filtering globally on all spanning tree edge ports. BPDU Filtering prevents a port from sending or receiving any BPDUs.

Caution

Be cautious when using this command; incorrect usage can cause bridging loops.

You can override the global effects of this spanning-tree port type edge bpdufilter default command by configuring BPDU Filtering at the interface level. See the spanning-tree bpdufilter command for complete information on using this feature at the interface level.

Note

The BPDU Filtering feature’s functionality is different when you enable it on a per-port basis or globally. When enabled globally, BPDU Filtering is applied only on ports that are operational spanning tree edge ports. Ports send a few BPDUs at a linkup before they effectively filter outbound BPDUs. If a BPDU is received on an edge port, that port immediately becomes a normal spanning tree port with all the normal transitions and BPDU Filtering is disabled. When enabled locally on a port, BPDU Filtering prevents the switch from receiving or sending BPDUs on this port.

Usage Guidelines

Use this command to automatically configure all interfaces as spanning tree edge ports by default. This command will not work on trunk ports.

Caution

Be careful when using this command. You should use this command only with interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data-packet loop and disrupt the switch and network operation.

When a linkup occurs, an interface configured as an edge port automatically moves the interface directly to the spanning tree forwarding state without waiting for the standard forward-time delay. (This transition was previously configured as the Cisco-proprietary PortFast feature.)

When you use this command, the system returns a message similar to the following:

Warning: this command enables portfast by default on all interfaces. You
 should now disable portfast explicitly on switched ports leading to hubs,
 switches and bridges as they may create temporary bridging loops.

You can configure individual interfaces as edge ports using the spanning-tree port type edge command.

The default spanning tree port type is normal.

Usage Guidelines

Use this command to configure an interface that connects to a switch as a spanning tree network port. Bridge Assurance runs only on Spanning Tree Protocol (STP) network ports.

Note	If you mistakenly configure ports connected to hosts as STP network ports and enable Bridge Assurance, those ports will automatically move into the blocking state.

Note	Bridge Assurance is enabled by default, and all interfaces configured as spanning tree network ports have Bridge Assurance enabled.

To configure a port as a spanning tree network port, use the spanning-tree port type network command. To remove this configuration, use the no spanning-tree port type normal command. When you use the no spanning-tree port type command, the software returns the port to the global default setting for network port types.

You can configure all ports that are connected to switches as spanning tree network ports by default by entering the spanning-tree port type network default command.

The default spanning tree port type is normal.

Usage Guidelines

Use this command to automatically configure all interfaces that are connected to switches as spanning tree network ports by default. You can then use the spanning-tree port type edge command to configure specified ports that are connected to hosts as spanning-tree edge ports.

Note	If you mistakenly configure ports connected to hosts as Spanning Tree Protocol (STP) network ports and Bridge Assurance is enabled, those ports will automatically move into the blocking state.

Configure only the ports that connect to other switches as network ports because the Bridge Assurance feature causes network ports that are connected to hosts to move into the spanning tree blocking state.

You can identify individual interfaces as network ports by using the spanning-tree port type network command.

The default spanning tree port type is normal.

Usage Guidelines

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

Caution

When disabling spanning tree on a VLAN using the no spanning-tree vlan vlan-id co mmand, ensure that all switches and bridges in the VLAN have spanning tree disabled. You cannot disable spanning tree on some switches and bridges in a VLAN and leave it enabled on other switches and bridges in the same VLAN because switches and bridges with spanning tree enabled have incomplete information about the physical topology of the network.

Caution

We do not recommend disabling spanning tree even in a topology that is free of physical loops. Spanning tree is a safeguard against misconfigurations and cabling errors. Do not disable spanning tree in a VLAN without ensuring that there are no physical loops present in the VLAN.

When setting the max-age seconds , if a bridge does not see BPDUs from the root bridge within the specified interval, it assumes that the network has changed and recomputes the spanning-tree topology.

The spanning-tree root primary alters this switch’s bridge priority to 24576. If you enter the spanning-tree root primary command and the switch does not become the root, then the bridge priority is changed to 4096 less than the bridge priority of the current bridge. The command fails if the value required to be the root bridge is less than 1. If the switch does not become the root, an error results.

If the network devices are set for the default bridge priority of 32768 and you enter the spanning-tree root secondary command, the software alters the bridge priority of the current bridge to 28762. If the root switch fails, this switch becomes the next root switch.

Use the spanning-tree root commands on the backbone switches only.

Usage Guidelines

Use this command in a topology with hybrid switches (for example, a virtual port channel [vPC] connected to a non-vPC switch) to configure VLAN-based load balancing.

To meet the VLAN-based load-balancing criteria, you must configure a different Spanning Tree Protocol (STP) bridge priority value for the root bridge and the designated bridge.

This command does not require a license.

Usage Guidelines

Do not use the vlan vlan-id parameter on access ports. The software uses the port priority value for access ports and the VLAN port priority values for trunk ports.

The priority values are 0, 32, 64, 96, 128, 160, 192, and 224. All other values are rejected.

Note	Use this command to configure the port priority for Rapid per VLAN Spanning Tree Plus (Rapid PVST+) spanning tree mode, which is the default STP mode. To configure the port priority for Multiple Spanning Tree (MST) spanning tree mode, use the spacing-tree mst port-priority command.

Usage Guidelines

The first 8 ports of a Cisco Nexus 5010 switch and the first 16 ports of a Cisco Nexus 5020 switch are switchable 1-Gigabit and 10-Gigabit ports. The default interface speed is 10-Gigabit. To configure these ports for 1-Gigabit Ethernet, insert a 1-Gigabit Ethernet SFP transceiver into the applicable port and then set its speed with the speed command.

Note

If the interface and transceiver speed is mismatched, the SFP validation failed message is displayed when you enter the show interface ethernet slot /port command. For example, if you insert a 1-Gigabit SFP transceiver into a port without configuring the speed 1000 command, you will get this error.By default, all ports on a Cisco Nexus 5000 Series switch are 10 Gigabits.

Usage Guidelines

You cannot suspend the state for VLAN 1 or VLANs 1006 to 4094.

VLANs in the suspended state do not pass packets.

Usage Guidelines

This command does not require a license.

Usage Guidelines

You must use the feature interface-vlan or the svi enable command before you can create VLAN interfaces.

Usage Guidelines

When enabled (the default), any virtual Ethernet interfaces that are in the administratively down state will be deleted after confirming with the vCenter server that no corresponding vNICs are in use.

This command does not require a license.

Usage Guidelines

Only one SVS connection can be enabled per session.

This command does not require a license.

Usage Guidelines

The primary VLANs do not need to be explicitly added to the allowed VLAN list. They are added automatically once there is a mapping between primary and secondary VLANs.

Usage Guidelines

This command does not require a license.

Usage Guidelines

There is no run-time effect on the port unless it is in private VLAN-host mode. If the port is in private VLAN-host mode but neither of the VLANs exist, the command is allowed but the port is made inactive. The port also may be inactive when the association between the private VLANs is suspended.

The secondary VLAN may be an isolated or community VLAN.

See the private-vlan command for more information on pr imary VLANs, secondary VLANS, and isolated or community ports.

Note	A private VLAN-isolated port on a Cisco Nexus 5000 Series switch running the current release of Cisco NX-OS does not support IEEE 802.1Q encapsulation and cannot be used as a trunk port.

Usage Guidelines

The secondary VLAN should be an isolated VLAN. Only one isolated VLAN under a given primary VLAN can be associated to an isolated trunk port.

Usage Guidelines

This command is applicable to the following Cisco Nexus 5000 Series switches:

• Cisco Nexus 5010 Series
• Cisco Nexus 5020 Series

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

This command does not require a license.

Usage Guidelines

When you configure a port as a host private VLAN port and one of the following applies, the port becomes inactive:

• The port does not have a valid private VLAN association configured.
• The port is a Switched Port Analyzer (SPAN) destination.
• The private VLAN association is suspended.

If you delete a private VLAN port association or if you configure a private port as a SPAN destination, the deleted private VLAN port association or the private port that is configured as a SPAN destination becomes inactive.

Note	We recommend that you enable spanning tree BPDU Guard on all private VLAN host ports.

Usage Guidelines

In a private VLAN domain, isolated trunks are part of a secondary VLAN. Isolated trunk ports can carry multiple isolated VLANs.

Usage Guidelines

When you configure a port as a promiscuous private VLAN port and one of the following applies, the port becomes inactive:

• The port does not have a valid private VLAN mapping configured.
• The port is a Switched Port Analyzer (SPAN) destination.

If you delete a private VLAN port mapping or if you configure a private port as a SPAN destination, the deleted private VLAN port mapping or the private port that is configured as a SPAN destination becomes inactive.

See the private-vlan command for more information on promiscuous ports.