user manual
Table Of Contents
- Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
- Contents
- Preface
- New and Changed Information for this Release
- Overview
- Configuring Ethernet Interfaces
- Information About Ethernet Interfaces
- Configuring Ethernet Interfaces
- Configuring the UDLD Mode
- Changing an Interface Port Mode
- Configuring Interface Speed
- Disabling Link Negotiation
- Configuring the CDP Characteristics
- Enabling or Disabling CDP
- Enabling the Error-Disabled Detection
- Enabling the Error-Disabled Recovery
- Configuring the Error-Disabled Recovery Interval
- Configuring the Debounce Timer
- Configuring the Description Parameter
- Disabling and Restarting Ethernet Interfaces
- Displaying Interface Information
- Displaying Input Packet Discard Information
- Default Physical Ethernet Settings
- Configuring VLANs
- Configuring Private VLANs
- Information About Private VLANs
- Guidelines and Limitations for Private VLANs
- Configuring a Private VLAN
- Enabling Private VLANs
- Configuring a VLAN as a Private VLAN
- Associating Secondary VLANs with a Primary Private VLAN
- Configuring an Interface as a Private VLAN Host Port
- Configuring an Interface as a Private VLAN Promiscuous Port
- Configuring a Promiscuous Trunk Port
- Configuring an Isolated Trunk Port
- Configuring the Allowed VLANs for PVLAN Trunking Ports
- Configuring Native 802.1Q VLANs on Private VLANs
- Verifying the Private VLAN Configuration
- Configuring Access and Trunk Interfaces
- Configuring Switching Modes
- Configuring Rapid PVST+
- Information About Rapid PVST+
- Understanding STP
- Understanding Rapid PVST+
- Rapid PVST+ and IEEE 802.1Q Trunks
- Rapid PVST+ Interoperation with Legacy 802.1D STP
- Rapid PVST+ Interoperation with 802.1s MST
- Configuring Rapid PVST+
- Enabling Rapid PVST+
- Enabling Rapid PVST+ per VLAN
- Configuring the Root Bridge ID
- Configuring a Secondary Root Bridge
- Configuring the Rapid PVST+ Port Priority
- Configuring the Rapid PVST+ Pathcost Method and Port Cost
- Configuring the Rapid PVST+ Bridge Priority of a VLAN
- Configuring the Rapid PVST+ Hello Time for a VLAN
- Configuring the Rapid PVST+ Forward Delay Time for a VLAN
- Configuring the Rapid PVST+ Maximum Age Time for a VLAN
- Specifying the Link Type
- Restarting the Protocol
- Verifying Rapid PVST+ Configurations
- Information About Rapid PVST+
- Configuring Multiple Spanning Tree
- Information About MST
- Configuring MST
- MST Configuration Guidelines
- Enabling MST
- Entering MST Configuration Mode
- Specifying the MST Name
- Specifying the MST Configuration Revision Number
- Specifying the Configuration on an MST Region
- Mapping and Unmapping VLANs to MST Instances
- Mapping Secondary VLANs to Same MSTI as Primary VLANs for Private VLANs
- Configuring the Root Bridge
- Configuring a Secondary Root Bridge
- Configuring the Port Priority
- Configuring the Port Cost
- Configuring the Switch Priority
- Configuring the Hello Time
- Configuring the Forwarding-Delay Time
- Configuring the Maximum-Aging Time
- Configuring the Maximum-Hop Count
- Configuring PVST Simulation Globally
- Configuring PVST Simulation Per Port
- Specifying the Link Type
- Restarting the Protocol
- Verifying MST Configurations
- Configuring STP Extensions
- About STP Extensions
- Information About STP Extensions
- Configuring STP Extensions
- STP Extensions Configuration Guidelines
- Configuring Spanning Tree Port Types Globally
- Configuring Spanning Tree Edge Ports on Specified Interfaces
- Configuring Spanning Tree Network Ports on Specified Interfaces
- Enabling BPDU Guard Globally
- Enabling BPDU Guard on Specified Interfaces
- Enabling BPDU Filtering Globally
- Enabling BPDU Filtering on Specified Interfaces
- Enabling Loop Guard Globally
- Enabling Loop Guard or Root Guard on Specified Interfaces
- Verifying STP Extension Configuration
- About STP Extensions
- Configuring LLDP
- Configuring the MAC Address Table
- Configuring IGMP Snooping
- Configuring Traffic Storm Control
- INDEX
If you configure a port connected to another switch as an edge port, you might create a bridging loop.Note
Spanning Tree Network Ports
Network ports are connected only to switches or bridges. Configuring a port as "network" while Bridge
Assurance is enabled globally, enables Bridge Assurance on that port.
If you mistakenly configure ports that are connected to hosts or other edge devices, as spanning tree
network ports, those ports will automatically move into the blocking state.
Note
Spanning Tree Normal Ports
Normal ports can be connected to either hosts, switches, or bridges. These ports function as normal spanning
tree ports.
The default spanning tree interface is a normal port.
Understanding Bridge Assurance
You can use Bridge Assurance to protect against certain problems that can cause bridging loops in the network.
Specifically, you use Bridge Assurance to protect against a unidirectional link failure and a device that continues
to forward data traffic when it is no longer running the spanning tree algorithm.
Bridge Assurance is supported only by Rapid PVST+ and MST. Legacy 802.1D spanning tree does not
support Bridge Assurance.
Note
Bridge Assurance is enabled by default and can only be disabled globally. Also, Bridge Assurance can be
enabled only on spanning tree network ports that are point-to-point links. Finally, both ends of the link must
have Bridge Assurance enabled.
With Bridge Assurance enabled, BPDUs are sent out on all operational network ports, including alternate and
backup ports, for each hello time period. If the port does not receive a BPDU for a specified period, the port
moves into the blocking state and is not used in the root port calculation. Once that port receives a BPDU, it
resumes the normal spanning tree transitions.
Understanding BPDU Guard
Enabling BPDU Guard shuts down that interface if a BPDU is received.
You can configure BPDU Guard at the interface level. When configured at the interface level, BPDU Guard
shuts the port down as soon as the port receives a BPDU, regardless of the port type configuration.
When you configure BPDU Guard globally, it is effective only on operational spanning tree edge ports. In a
valid configuration, LAN edge interfaces do not receive BPDUs. A BPDU that is received by an edge LAN
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
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Configuring STP Extensions
Information About STP Extensions