Deployment Guide
Table Of Contents
- Dell EMC Networking Configuration Guide for the C9010 Series Version 9.14.2.1
- About this Guide
- Configuration Fundamentals
- Getting Started
- Switch Management
- Configuring Privilege Levels
- Configuring Logging
- Track Login Activity
- Limit Concurrent Login Sessions
- Enabling Secured CLI Mode
- Log Messages in the Internal Buffer
- Disabling System Logging
- Sending System Messages to a Syslog Server
- Display the Logging Buffer and the Logging Configuration
- Changing System Logging Settings
- Configuring a UNIX Logging Facility Level
- Synchronizing Log Messages
- Enabling Timestamp on Syslog Messages
- File Transfer Services
- Terminal Lines
- Setting Time Out of EXEC Privilege Mode
- Using Telnet to Access Another Network Device
- Lock CONFIGURATION Mode
- LPC Bus Quality Degradation
- Recovering from a Forgotten Password
- Ignoring the Startup Configuration and Booting from the Factory-Default Configuration
- Recovering from a Failed Start
- Restoring Factory-Default Settings
- Using Hashes to Verify Software Images Before Installation
- Verifying System Images on C9010 Components
- Viewing the Reason for Last System Reboot
- 802.1X
- The Port-Authentication Process
- Configuring 802.1X
- Important Points to Remember
- Enabling 802.1X
- Configuring dot1x Profile
- Configuring MAC addresses for a do1x Profile
- Configuring the Static MAB and MAB Profile
- Configuring Critical VLAN
- Configuring Request Identity Re-Transmissions
- Configuring a Quiet Period after a Failed Authentication
- Forcibly Authorizing or Unauthorizing a Port
- Re-Authenticating a Port
- Configuring Dynamic VLAN Assignment with Port Authentication
- Guest and Authentication-Fail VLANs
- Multi-Host Authentication
- Multi-Supplicant Authentication
- MAC Authentication Bypass
- Dynamic CoS with 802.1X
- Access Control Lists (ACLs)
- IP Access Control Lists (ACLs)
- ACL Optimization to Increase Number of Supported IPv4 ACLs
- IP Fragment Handling
- Configure a Standard IP ACL
- Configure an Extended IP ACL
- Configure Layer 2 and Layer 3 ACLs
- Using ACL VLAN Groups
- Applying an IP ACL
- IP Prefix Lists
- ACL Remarks
- ACL Resequencing
- Route Maps
- Important Points to Remember
- Configuring a UDF ACL
- Hot-Lock Behavior
- Bidirectional Forwarding Detection (BFD)
- Border Gateway Protocol IPv4 (BGPv4)
- Autonomous Systems (AS)
- Sessions and Peers
- Route Reflectors
- BGP Attributes
- Multiprotocol BGP
- Implement BGP
- Configuration Information
- BGP Configuration
- Enabling BGP
- Configuring AS4 Number Representations
- Configuring Peer Groups
- Configuring BGP Fast Fail-Over
- Configuring Passive Peering
- Maintaining Existing AS Numbers During an AS Migration
- Allowing an AS Number to Appear in its Own AS Path
- Filtering on an AS-Path Attribute
- Regular Expressions as Filters
- Redistributing Routes
- Enabling Additional Paths
- Configuring IP Community Lists
- Configuring an IP Extended Community List
- Filtering Routes with Community Lists
- Manipulating the COMMUNITY Attribute
- Changing MED Attributes
- Changing the LOCAL_PREFERENCE Attribute
- Configuring the local System or a Different System to be the Next Hop for BGP-Learned Routes
- Changing the WEIGHT Attribute
- Enabling Multipath
- Filtering BGP Routes
- Filtering BGP Routes Using Route Maps
- Filtering BGP Routes Using AS-PATH Information
- Configuring BGP Route Reflectors
- Aggregating Routes
- Configuring BGP Confederations
- Enabling Route Flap Dampening
- Changing BGP Timers
- Setting the extended timer
- Enabling BGP Neighbor Soft-Reconfiguration
- Enabling or disabling BGP neighbors
- Route Map Continue
- Enabling MBGP Configurations
- BGP Regular Expression Optimization
- Debugging BGP
- Sample Configurations
- Content Addressable Memory (CAM)
- Control Plane Policing (CoPP)
- Data Center Bridging (DCB)
- Enabling Data Center Bridging
- Ethernet Enhancements in Data Center Bridging
- QoS dot1p Traffic Classification and Queue Assignment
- SNMP Support for PFC and Buffer Statistics Tracking
- DCB Maps and its Attributes
- Data Center Bridging: Default Configuration
- Configuration Notes: PFC and ETS in a DCB Map
- Configuring Priority-Based Flow Control
- Configuring Enhanced Transmission Selection
- Configure a DCBx Operation
- DCBx Operation
- DCBx Port Roles
- DCB Configuration Exchange
- Configuration Source Election
- Propagation of DCB Information
- Auto-Detection and Manual Configuration of the DCBx Version
- Behavior of Tagged Packets
- Configuration Example for DSCP and PFC Priorities
- DCBx Example
- DCBx Prerequisites and Restrictions
- Configuring DCBx
- Verifying the DCB Configuration
- Performing PFC Using DSCP Bits Instead of 802.1p Bits
- PFC and ETS Configuration Examples
- Using PFC and ETS to Manage Data Center Traffic
- Priority-Based Flow Control Using Dynamic Buffer Method
- Configuring the Dynamic Buffer Method
- Debugging and Diagnostics
- Dynamic Host Configuration Protocol (DHCP)
- DHCP Packet Format and Options
- Assign an IP Address using DHCP
- Implementation Information
- Configure the System to be a DHCP Server
- Configure the System to be a Relay Agent
- Configure the System to be a DHCP Client
- DHCP Relay When DHCP Server and Client are in Different VRFs
- Non-default VRF configuration for DHCPv6 helper address
- Configuring DHCP relay source interface
- Configure Secure DHCP
- Source Address Validation
- Equal Cost Multi-Path (ECMP)
- FCoE Transit
- FIPS Cryptography
- Flex Hash and Optimized Boot-Up
- Force10 Resilient Ring Protocol (FRRP)
- GARP VLAN Registration Protocol (GVRP)
- High Availability (HA)
- Internet Group Management Protocol (IGMP)
- Interfaces
- Port Numbering
- Interface Types
- View Basic Interface Information
- Resetting an Interface to its Factory Default State
- Enabling a Physical Interface
- Physical Interfaces
- Egress Interface Selection (EIS)
- Management Interfaces
- Port Extender Interfaces
- VLAN Interfaces
- Loopback Interfaces
- Null Interfaces
- Port Channel Interfaces
- Port Channel Definition and Standards
- Port Channel Benefits
- Port Channel Implementation
- 10/40 Gbps Interfaces in Port Channels
- Configuration Tasks for Port Channel Interfaces
- Creating a Port Channel
- Adding a Physical Interface to a Port Channel
- Reassigning an Interface to a New Port Channel
- Configuring the Minimum Oper Up Links in a Port Channel
- Adding or Removing a Port Channel from a VLAN
- Assigning an IP Address to a Port Channel
- Deleting or Disabling a Port Channel
- Load Balancing Through Port Channels
- Changing the Hash Algorithm
- Bulk Configuration
- Defining Interface Range Macros
- Monitoring and Maintaining Interfaces
- Displaying Traffic Statistics on HiGig Ports
- Link Bundle Monitoring
- Monitoring HiGig Link Bundles
- Non Dell-Qualified Transceivers
- Splitting QSFP Ports to SFP+ Ports
- Configuring wavelength for 10–Gigabit SFP+ optics
- Link Dampening
- Using Ethernet Pause Frames for Flow Control
- Configure the MTU Size on an Interface
- Auto-Negotiation on Ethernet Interfaces
- Provisioning Combo Ports
- View Advanced Interface Information
- Configuring the Traffic Sampling Size Globally
- Dynamic Counters
- Internet Protocol Security (IPSec)
- IPv4 Routing
- IP Addresses
- Configuration Tasks for IP Addresses
- Assigning IP Addresses to an Interface
- Configuring Static Routes
- Configure Static Routes for the Management Interface
- Enabling Directed Broadcast
- Resolution of Host Names
- Enabling Dynamic Resolution of Host Names
- Specifying the Local System Domain and a List of Domains
- Configuring DNS with Traceroute
- ARP
- ICMP
- ICMP Redirects
- IPv6 Routing
- Protocol Overview
- IPv6 Implementation on the Dell Networking OS
- Configuring the LPM Table for IPv6 Extended Prefixes
- ICMPv6
- Path MTU Discovery
- IPv6 Neighbor Discovery
- Secure Shell (SSH) Over an IPv6 Transport
- Configuration Tasks for IPv6
- Adjusting Your CAM Profile
- Assigning an IPv6 Address to an Interface
- Assigning a Static IPv6 Route
- Configuring Telnet with IPv6
- SNMP over IPv6
- Displaying IPv6 Information
- Displaying an IPv6 Configuration
- Displaying IPv6 Routes
- Displaying the Running Configuration for an Interface
- Clearing IPv6 Routes
- Disabling ND Entry Timeout
- Configuring IPv6 RA Guard
- Intermediate System to Intermediate System
- IS-IS Protocol Overview
- IS-IS Addressing
- Multi-Topology IS-IS
- Graceful Restart
- Implementation Information
- Configuration Information
- IS-IS Metric Styles
- Configure Metric Values
- Sample Configurations
- iSCSI Optimization
- iSCSI Optimization Overview
- Default iSCSI Optimization Values
- iSCSI Optimization Prerequisites
- Configuring iSCSI Optimization
- Displaying iSCSI Optimization Information
- Enable and Disable iSCSI Optimization
- Synchronizing iSCSI Sessions Learned on VLT-Lags with VLT-Peer
- Monitoring iSCSI Traffic Flows
- Information Monitored in iSCSI Traffic Flows
- Detection and Auto-Configuration for Dell EqualLogic Arrays
- Configuring Detection and Ports for Dell Compellent Arrays
- Application of Quality of Service to iSCSI Traffic Flows
- Link Aggregation Control Protocol (LACP)
- Layer 2
- Manage the MAC Address Table
- MAC Learning Limit
- Setting the MAC Learning Limit
- mac learning-limit Dynamic
- mac learning-limit mac-address-sticky
- mac learning-limit station-move
- mac learning-limit no-station-move
- Learning Limit Violation Actions
- Setting Station Move Violation Actions
- Recovering from Learning Limit and Station Move Violations
- Disabling MAC Address Learning on the System
- Enabling port security
- NIC Teaming
- Configure Redundant Pairs
- Far-End Failure Detection
- Link Layer Discovery Protocol (LLDP)
- 802.1AB (LLDP) Overview
- Optional TLVs
- TIA-1057 (LLDP-MED) Overview
- Configure LLDP
- CONFIGURATION versus INTERFACE Configurations
- Enabling LLDP
- Enabling LLDP on Management Ports
- Advertising TLVs
- Storing and Viewing Unrecognized LLDP TLVs
- Viewing the LLDP Configuration
- Viewing Information Advertised by Adjacent LLDP Neighbors
- Configuring LLDPDU Intervals
- Configuring LLDP Notification Interval
- Configuring Transmit and Receive Mode
- Configuring a Time to Live
- Debugging LLDP
- Relevant Management Objects
- Multicast Source Discovery Protocol (MSDP)
- Anycast RP
- Implementation Information
- Configure Multicast Source Discovery Protocol
- Enable MSDP
- Manage the Source-Active Cache
- Accept Source-Active Messages that Fail the RFP Check
- Specifying Source-Active Messages
- Limiting the Source-Active Messages from a Peer
- Preventing MSDP from Caching a Local Source
- Preventing MSDP from Caching a Remote Source
- Preventing MSDP from Advertising a Local Source
- Logging Changes in Peership States
- Terminating a Peership
- Clearing Peer Statistics
- Debugging MSDP
- MSDP with Anycast RP
- Configuring Anycast RP
- MSDP Sample Configurations
- Multiple Spanning Tree Protocol (MSTP)
- Spanning Tree Variations
- Configure Multiple Spanning Tree Protocol
- Enable Multiple Spanning Tree Globally
- Adding and Removing Interfaces
- Creating Multiple Spanning Tree Instances
- Influencing MSTP Root Selection
- Interoperate with Non-Dell Bridges
- Changing the Region Name or Revision
- Modifying Global Parameters
- Modifying the Interface Parameters
- Configuring an EdgePort
- Flush MAC Addresses after a Topology Change
- MSTP Sample Configurations
- Debugging and Verifying MSTP Configurations
- Multicast Features
- Multicast Listener Discovery Protocol
- Object Tracking
- Open Shortest Path First (OSPFv2 and OSPFv3)
- Protocol Overview
- OSPF Implementation
- Configuration Information
- Configuration Task List for OSPFv2 (OSPF for IPv4)
- Enabling OSPFv2
- Assigning a Router ID
- Enabling Multi-Process OSPF (OSPFv2, IPv4 Only)
- Assigning an OSPFv2 Area
- Enable OSPFv2 on Interfaces
- Configuring Stub Areas
- Configuring LSA Throttling Timers
- Enabling Passive Interfaces
- Enabling Fast-Convergence
- Changing OSPFv2 Parameters on Interfaces
- Enabling OSPFv2 Authentication
- Creating Filter Routes
- Applying Prefix Lists
- Redistributing Routes
- Troubleshooting OSPFv2
- Configuration Task List for OSPFv2 (OSPF for IPv4)
- Sample Configurations for OSPFv2
- OSPFv3 NSSA
- Configuration Task List for OSPFv3 (OSPF for IPv6)
- Enabling IPv6 Unicast Routing
- Assigning IPv6 Addresses on an Interface
- Assigning Area ID on an Interface
- Assigning OSPFv3 Process ID and Router ID Globally
- Assigning OSPFv3 Process ID and Router ID to a VRF
- Configuring the Cost of OSPFv3 Routes
- Configuring Stub Areas
- Configuring Passive-Interface
- Redistributing Routes
- Configuring a Default Route
- OSPFv3 Authentication Using IPsec
- Troubleshooting OSPFv3
- MIB Support for OSPFv3
- Per-VLAN Spanning Tree Plus (PVST+)
- Protocol Overview
- Implementation Information
- Configure Per-VLAN Spanning Tree Plus
- Enabling PVST+
- Disabling PVST+
- Influencing PVST+ Root Selection
- Modifying Global PVST+ Parameters
- Modifying Interface PVST+ Parameters
- Configuring an EdgePort
- PVST+ in Multi-Vendor Networks
- Enabling PVST+ Extend System ID
- PVST+ Sample Configurations
- PIM Sparse-Mode (PIM-SM)
- PIM Source-Specific Mode (PIM-SSM)
- Policy-based Routing (PBR)
- Port Extenders (PEs)
- IEEE 802.1BR
- 802.1BR Terms and Definitions
- Enabling the Port Extender Feature
- Provisioning a Port Extender
- PE Selection Logic
- Managing a Port Extender
- Preventing Loops on Port Extender Ports
- Upgrading a Port Extender
- De-provisioning a Port Extender
- Scheduling PE reboots
- Troubleshooting a Port Extender
- Supported Features
- Dual Homing
- Port Extender (PE) Stacking
- Port Monitoring
- Power over Ethernet (PoE)
- Configuring PoE or PoE+
- Manage Ports using Power Priority and the Power Budget
- Setting the Threshold Limit for the PoE Power Budget
- Advertising the Extended Power through MDI
- Advertising Extended Power Though dot3–TLVs
- Detecting Legacy Devices and Allocating Power
- Deploying Voice Over IP (VoIP)
- Managing PoE on the Port Extender
- Private VLANs (PVLAN)
- Quality of Service (QoS)
- Implementation Information
- Port-Based QoS Configurations
- Policy-Based QoS Configurations
- DSCP Color Maps
- Enabling QoS Rate Adjustment
- Enabling Strict-Priority Queueing
- Weighted Random Early Detection
- Explicit Congestion Notification
- Using A Configurable Weight for WRED and ECN
- Pre-Calculating Available QoS CAM Space
- SNMP Support for Buffer Statistics Tracking
- Routing Information Protocol (RIP)
- Remote Monitoring (RMON)
- Rapid Spanning Tree Protocol (RSTP)
- Protocol Overview
- Configuring Rapid Spanning Tree
- Important Points to Remember
- Configuring Interfaces for Layer 2 Mode
- Enabling Rapid Spanning Tree Protocol Globally
- Adding and Removing Interfaces
- Modifying Global Parameters
- Modifying Interface Parameters
- Influencing RSTP Root Selection
- Configuring an EdgePort
- Configuring Fast Hellos for Link State Detection
- Security
- Role-Based Access Control
- AAA Accounting
- AAA Authentication
- AAA Authorization
- RADIUS
- RADIUS Authentication and Authorization
- Configuration Task List for RADIUS
- Support for Change of Authorization and Disconnect Messages packets
- Change of Authorization (CoA) packets
- Disconnect Messages
- Attributes
- Error-cause Values
- CoA Packet Processing
- CoA or DM Discard
- Disconnect Message Processing
- Configuring DAC
- Configuring the port number
- Configuring shared key
- Disconnecting administrative users logged in through RADIUS
- Configuring CoA to bounce 802.1x enabled ports
- Configuring CoA to re-authenticate 802.1x sessions
- Terminating the 802.1x user session
- Disabling 802.1x enabled port
- Important points to remember
- Configuring replay protection
- Rate-limiting RADIUS packets
- Configuring time-out value
- TACACS+
- Protection from TCP Tiny and Overlapping Fragment Attacks
- Enabling SCP and SSH
- Using SCP with SSH to Copy a Software Image
- Removing the RSA Host Keys and Zeroizing Storage
- Configuring When to Re-generate an SSH Key
- Configuring the SSH Server Cipher List
- Configuring DNS in the SSH Server
- Configuring the HMAC Algorithm for the SSH Server
- Configuring the HMAC Algorithm for the SSH Client
- Configuring the SSH Server Cipher List
- Configuring the SSH Client Cipher List
- Secure Shell Authentication
- Troubleshooting SSH
- Telnet
- VTY Line and Access-Class Configuration
- Two Factor Authentication (2FA)
- Configuring the System to Drop Certain ICMP Reply Messages
- Dell EMC Networking OS Security Hardening
- Service Provider Bridging
- sFlow
- Simple Network Management Protocol (SNMP)
- Protocol Overview
- Implementation Information
- Configuration Task List for SNMP
- Important Points to Remember
- Set up SNMP
- Reading Managed Object Values
- Writing Managed Object Values
- Configuring Contact and Location Information using SNMP
- Configuring the CPU Utilization for SNMP Traps
- Configuring Threshold Memory Utilization for SNMP Traps
- Subscribing to Managed Object Value Updates using SNMP
- Enabling a Subset of SNMP Traps
- Enabling an SNMP Agent to Notify Syslog Server Failure
- Copy Configuration Files Using SNMP
- Copying a Configuration File
- Copying Configuration Files via SNMP
- Copying the Startup-Config Files to the Running-Config
- Copying the Startup-Config Files to the Server via FTP
- Copying the Startup-Config Files to the Server via TFTP
- Copy a Binary File to the Startup-Configuration
- Additional MIB Objects to View Copy Statistics
- Obtaining a Value for MIB Objects
- MIB Support to Display Reason for Last System Reboot
- MIB Support to Display the Available Partitions on Flash
- MIB Support to Display Egress Queue Statistics
- MIB Support to Display Egress Queue Statistics
- MIB Support for entAliasMappingTable
- SNMP Support for WRED Green/Yellow/Red Drop Counters
- MIB Support for LAG
- MIB Support to Display Unrecognized LLDP TLVs
- MIB support for Port Security
- Manage VLANs using SNMP
- Managing Overload on Startup
- Enabling and Disabling a Port using SNMP
- Fetch Dynamic MAC Entries using SNMP
- Deriving Interface Indices
- Monitoring BGP sessions via SNMP
- Monitor Port-Channels
- Troubleshooting SNMP Operation
- Transceiver Monitoring
- Configuring SNMP context name
- Storm Control
- Spanning Tree Protocol (STP)
- Protocol Overview
- Configure Spanning Tree
- Important Points to Remember
- Configuring Interfaces for Layer 2 Mode
- Enabling Spanning Tree Protocol Globally
- Adding an Interface to the Spanning Tree Group
- Modifying Global Parameters
- Modifying Interface STP Parameters
- Enabling PortFast
- Preventing Network Disruptions with BPDU Guard
- Selecting STP Root
- STP Root Guard
- Enabling SNMP Traps for Root Elections and Topology Changes
- STP Loop Guard
- Displaying STP Guard Configuration
- SupportAssist
- System Time and Date
- Tunneling
- Upgrade Procedures
- Uplink Failure Detection (UFD)
- Virtual LANs (VLANs)
- VLT Proxy Gateway
- Virtual Routing and Forwarding (VRF)
- Virtual Link Trunking (VLT)
- Overview
- VLT Terminology
- Important Points to Remember
- Configuration Notes
- Primary and Secondary VLT Peers
- RSTP and VLT
- VLT Bandwidth Monitoring
- VLT and High Availability
- VLT and IGMP Snooping
- VLT and Stacking
- VLT IPv6
- VLT Port Delayed Restoration
- PIM-Sparse Mode Support on VLT
- VLT Routing
- Non-VLT ARP Sync
- RSTP Configuration
- Configuring VLT
- Configuring a VLT Interconnect
- Enabling VLT and Creating a VLT Domain
- Configuring a VLT Backup Link
- Configuring a VLT Port Delay Period
- Reconfiguring the Default VLT Settings (Optional)
- Connecting a VLT Domain to an Attached Access Device (Switch or Server)
- Configuring a VLT VLAN Peer-Down (Optional)
- Configuring Enhanced VLT (eVLT) (Optional)
- VLT Sample Configuration
- eVLT Configuration Example
- PIM-Sparse Mode Configuration Example
- Verifying a VLT Configuration
- Additional VLT Sample Configurations
- Troubleshooting VLT
- Reconfiguring Stacked Switches as VLT
- Specifying VLT Nodes in a PVLAN
- Configuring a VLT VLAN or LAG in a PVLAN
- Proxy ARP Capability on VLT Peer Nodes
- VLT Nodes as Rendezvous Points for Multicast Resiliency
- Configuring VLAN-Stack over VLT
- Virtual Router Redundancy Protocol (VRRP)
- VRRP Overview
- VRRP Benefits
- VRRP Implementation
- VRRP Configuration
- Configuration Task List
- Creating a Virtual Router
- Configuring the VRRP Version for an IPv4 Group
- Assign Virtual IP addresses
- Configuring a Virtual IP Address
- Setting VRRP Group (Virtual Router) Priority
- Configuring VRRP Authentication
- Disabling Preempt
- Changing the Advertisement Interval
- Setting VRRP Initialization Delay
- Track an Interface or Object
- Tracking an Interface
- Configuration Task List
- Sample Configurations
- Proxy Gateway with VRRP
- Standards Compliance
- X.509v3
- Introduction to X.509v3 certification
- X.509v3 support in Dell Networking OS
- Information about installing CA certificates
- Information about Creating Certificate Signing Requests (CSR)
- Information about installing trusted certificates
- Transport layer security (TLS)
- Online certificate status protocol (OSCP)
- Verifying certificates
- Event logging
4. Optionally, for load balancing, select a nondefault bridge-priority for a VLAN.
Related Configuration Tasks
● Modifying Global PVST+ Parameters
● Modifying Interface PVST+ Parameters
● Configuring an EdgePort
● Flush MAC Addresses after a Topology Change
● Prevent Network Disruptions with BPDU Guard
● Enabling SNMP Traps for Root Elections and Topology Changes
● PVST+ in Multi-Vendor Networks
● Enabling PVST+ Extended System ID
● PVST+ Sample Configurations
Enabling PVST+
When you enable PVST+, the system instantiates STP on each active VLAN.
1. Enter PVST context.
PROTOCOL PVST mode
protocol spanning-tree pvst
2. Enable PVST+.
PROTOCOL PVST mode
no disable
Disabling PVST+
To disable PVST+ globally or on an interface, use the following commands.
● Disable PVST+ globally.
PROTOCOL PVST mode
disable
● Disable PVST+ on an interface, or remove a PVST+ parameter configuration.
INTERFACE mode
no spanning-tree pvst
To display your PVST+ configuration, use the show config command from PROTOCOL PVST mode.
Dell_E600(conf-pvst)#show config verbose
!
protocol spanning-tree pvst
no disable
vlan 100 bridge-priority 4096
Influencing PVST+ Root Selection
As shown in the previous PVST+ illustration, all VLANs use the same forwarding topology because R2 is elected the root, and all
TengigabitEthernet ports have the same cost.
The following per-VLAN spanning tree illustration changes the bridge priority of each bridge so that a different forwarding
topology is generated for each VLAN. This behavior demonstrates how you can use PVST+ to achieve load balancing.
664
Per-VLAN Spanning Tree Plus (PVST+)