Juniper Networks EX2500 manual Per Vlan Rapid Spanning Tree, Default Spanning Tree Configuration

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Chapter 3: Spanning Tree Protocol

Per VLAN Rapid Spanning Tree

Per VLAN Rapid Spanning Tree Plus Protocol (PVRST+) enhances the RSTP protocol by adding the ability to have multiple Spanning Tree Groups (STGs). PVRST+ is based on IEEE 802.1w Rapid Spanning Tree Protocol.

In PVRST mode, the EX2500 switch supports a maximum of 128 Spanning Tree Groups (STGs). Multiple STGs provide multiple data paths, which can be used for load balancing and redundancy.

To enable load balancing between two EX2500 switches using multiple STGs, configure each path with a different VLAN and then assign each VLAN to a separate STG. Each STG is independent. Each STG sends its own Bridge Protocol Data Units (BPDUs), and each STG must be configured independently.

The STG, or bridge group, forms a loop-free topology that includes one or more virtual LANs (VLANs). The switch supports 128 STGs running simultaneously. The default STG 1 may contain multiple VLANs. STGs 2 through 128 each may contain only one VLAN.

Default Spanning Tree Configuration

In the default configuration, a single STG (STG 1) includes all non-management ports on the switch. This is called the default STG. Although ports can be added to or deleted from the default STG, the default STG cannot be deleted from the system.

All other STGs, except the default STG 1, are empty and you must assign a VLAN to the STG. However, you cannot assign ports directly to an STG. Instead, you add ports to a VLAN and add the VLAN to the STG. Each STG is enabled by default, and assigned an ID number from 2 to 128.

By default, the spanning tree on the management port is turned off.

Why Do We Need Multiple Spanning Trees?

The following examples describe why we need multiple spanning trees.

In Figure 7, VLAN 1 and VLAN 2 pass traffic between switch 1 and switch 2. If you have a single Spanning Tree Group, the switches see an apparent physical loop, and one VLAN might become blocked, affecting connectivity, even though no logical loop exists. VLAN 2 traffic is blocked unnecessarily.

Figure 7: Two VLANs on One Spanning Tree Group

	VLAN 1, STG 1

Switch 1			X	Switch 2

VLAN 2, STG 1

VLAN 2 traffic blocked by STG 1

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Contents North Mathilda Avenue Sunnyvale, CA Configuration GuideIi „ Table of Contents Chapter VLANs Rmon Overview Rmon Group 1-Statistics Rmon Group 2-History Chapter Ports and TrunkingPort Mirroring Overview Configuring Port Mirroring AppendixesIndexes Port-Based Vlan Assignment Default Vlan SettingsPage List of Tables EX2500 Ethernet Switch Configuration Guide „ List of Tables Supported Platforms About This GuideObjectives AudienceIcon Meaning Description Documentation ConventionsList of Technical Publications Documentation FeedbackRequesting Technical Support Opening a Case with Jtac Self-Help Online Tools and ResourcesEX2500 Ethernet Switch Applications Page Configuring the Management Interface Accessing the SwitchConfigure the default gateway. Enable the gateway Dynamic Host Configuration ProtocolUsing the EX2500 Web Device Manager Using TelnetConfiguring EX2500 Web Device Manager Access via Https Configuring EX2500 Web Device Manager Access via HttpSNMPv1, SNMPv2 Using SnmpDefault Configuration User ConfigurationSNMPv3 Configure an entry in the notify table Configuring Snmp Trap HostsSNMPv1 Trap Host Configuration SNMPv2 Trap Host ConfigurationSNMPv3 Trap Host Configuration Securing Access to the SwitchConfigure the Radius secret Radius Authentication and AuthorizationHow Radius Authentication Works Configuring Radius on the SwitchRadius Authentication Features in the EX2500 Switch Radius Attributes for EX2500 User Privileges Switch User AccountsTACACS+ Authentication How TACACS+ Authentication WorksTACACS+ Authentication Features in the EX2500 Switch „ starttime „ stoptime „ elapsedtime „ disccause Command Authorization and Logging Configuring TACACS+ Authentication on the SwitchConfigure the TACACS+ secret and second secret SSH Encryption of Management Messages Configuring SSH Features on the SwitchGenerating RSA Host and Server Keys for SSH Access Secure ShellSSH Integration with Radius and TACACS+ Authentication End User Access ControlUser Access Control Considerations for Configuring End User AccountsLogging In to an End User Account Listing Current UsersVlan Overview VLANsPvid Numbers „ Port configurationVLANs and Port Vlan ID Numbers Vlan NumbersVlan Tagging Illustrates the default Vlan settings on the switchDefault Vlan Settings Port-Based Vlan Assignment Vlan Topologies and Design Considerations Vlan Configuration RulesMultiple VLANs example in is described in Table Multiple VLANs Configuration ExampleEnable tagging on uplink ports that support multiple VLANs Private Vlan Ports Private VLANsVerify the configuration Private Vlan Configuration GuidelinesPrivate Vlan Configuration Example Configure a secondary Vlan and map it to the primary VlanSpanning Tree Overview Spanning Tree ProtocolBridge Protocol Data Units BPDUs Determining the Path for Forwarding BPDUsBridge Priority Port Path Cost Spanning Tree Group Configuration GuidelinesChanging the Spanning Tree Mode Port PriorityCreating a Vlan Rules for Vlan Tagged PortsAdding and Removing Ports from STGs Port State Changes Rapid Spanning Tree ProtocolEdge Port Rstp Configuration GuidelinesRstp Configuration Example Port Type and Link TypeDefault Spanning Tree Configuration Why Do We Need Multiple Spanning Trees?Per Vlan Rapid Spanning Tree Configuring Pvrst Pvrst Configuration GuidelinesCommon Internal Spanning Tree Mstp Configuration GuidelinesMultiple Spanning Tree Protocol Mstp RegionImplementing Multiple Spanning Tree Groups Multiple Spanning Tree Groups Configuration ExampleVlan Fast Uplink ConvergenceConfiguring Fast Uplink Convergence Configuration GuidelinesPorts and Trunking Trunking OverviewStatistical Load Distribution Built-In Fault Tolerance Before Configuring Static TrunksTrunk Group Configuration Rules Port Trunk Group Configuration Example Port Trunking Configuration ExampleFollow these steps on the EX2500 switch Define a trunk group „ Destination IP DIP Configurable Trunk Hash AlgorithmLink Aggregation Control Protocol „ Destination MAC Dmac48 „ Link Aggregation Control Protocol Set the Lacp mode Lacp Configuration GuidelinesConfiguring Lacp Optionally Reducing Lacp TimeoutEx2500config-if# lacp timeout short ex2500config-if# exit QoS Overview Quality of ServiceCOS Using ACL FiltersTo delete an IP Standard ACL MAC Extended ACLsIP Standard ACLs To delete a MAC Extended ACLTo delete an IP Extended ACL IP Extended ACLsTCP/UDP Understanding ACL PriorityACL Example 1-Blocking Traffic to a Host ACL Configuration ExamplesAssigning ACLs to a Port Viewing ACL StatisticsAdd the ACL to a port ACL Example 3-Blocking Http TrafficAssign the ACLs to a port ACL Example 4-Blocking All Except Certain PacketsUsing Storm Control Filters Configuring Storm ControlBroadcast Storms Differentiated Services Concepts Using Dscp Values to Provide QoSAssured Forwarding Drop Precedence Class Per Hop BehaviorUse the following command to perform Dscp mapping QoS LevelsDscp Mapping Shows the priority bits in a VLAN-tagged packet Using 802.1p Priority to Provide QoSQueuing and Scheduling Rmon Overview Remote MonitoringRmon Group 1-Statistics Configure the Rmon statistics on a portRmon Group 2-History Configuring Rmon HistoryConfigure the Rmon History parameters for a port This configuration enables Rmon History collection on portConfigure the Rmon Alarm parameters to track Icmp messages Rmon Group 3-AlarmsAlarm MIB Objects Configuring Rmon AlarmsRmon Group 9-Events Ex2500config# rmon event 110 type log-onlyPage Igmp Snooping IgmpFastLeave IGMPv3 Snooping Igmp Snooping Configuration ExampleEx2500# show ip igmp groups Static Multicast RouterHigh Availability Overview High Availability Through Uplink Failure DetectionFailure Detection Pair Spanning Tree Protocol with UFD UFD Configuration GuidelinesMonitoring UFD UFD Configuration ExamplePage Appendixes EX2500 Ethernet Switch Configuration Guide 80 „ Appendixes Port Mirroring Overview „ Port Mirroring Overview on „ Configuring Port Mirroring onConfiguring Port Mirroring „ Index on IndexesEX2500 Ethernet Switch Configuration Guide 84 „ Indexes Numerics IndexInternet Group Management Protocol. See Igmp Management interface, configuringMulti-links between switches, port trunking Physical. See switch portsSegmentation. See IP subnets Segments. See IP subnets Quality of Service. See QoSQoS SecurityExample showing multiple VLANs Virtual Local Area Networks. See VLANs