Document Outline

• Contents
• Preface
  • Document conventions
    • Text formatting conventions
    • Command syntax conventions
    • Notes, cautions, and warnings
  • Brocade resources
  • Contacting Brocade Technical Support
  • Document feedback
• About This Document
  • What’s new in this document
  • Supported Hardware
  • How command information is presented in this guide
• Basic Layer 2 Features
  • Supported basic Layer 2 features
  • About port regions
    • FastIron X Series device port regions
    • FCX device port regions
    • ICX 6610 device port regions
    • ICX 6430 device port regions
    • ICX 6450 device port regions
    • ICX 6650 device port regions
    • ICX 7750 device port regions
  • Enabling or disabling the Spanning Tree Protocol (STP)
    • Modifying STP bridge and port parameters
  • Management MAC address for stackable devices
  • MAC learning rate control
  • Changing the MAC age time and disabling MAC address learning
    • Disabling the automatic learning of MAC addresses
      • MAC address learning configuration notes and feature limitations
    • Displaying the MAC address table
  • Static MAC entry configuration
    • Multi-port static MAC address
      • Multi-port static MAC address configuration notes
      • Configuring a multi-port static MAC address
  • VLAN-based static MAC entries configuration
    • Configuring a VLAN to drop static MAC entries
  • Clearing MAC address entries
  • Flow-based MAC address learning
    • Flow-based learning overview
      • The benefits of flow-based learning
      • How flow-based learning works
    • Flow-based learning configuration considerations
    • Configuring flow-based MAC address learning
      • Enabling flow-based MAC address learning
      • Increasing the capacity of the MAC address table (optional)
    • Displaying information about flow-based MACs
    • Clearing flow-based MAC address entries
  • Enabling port-based VLANs
    • Assigning IEEE 802.1Q tagging to a port
      • Command syntax for assigning 802.1Q tagging to a port
  • Defining MAC address filters
  • Monitoring MAC address movement
    • Configuring the MAC address movement threshold rate
    • Viewing the MAC address movement threshold rate configuration
    • Configuring an interval for collecting MAC address move notifications
    • Viewing MAC address movement statistics for the interval history
  • SNMP MAC-notification trap support
    • Requirements and limitations for MAC-notification trap support
    • Configuring SNMP traps for MAC-notification
    • MAC-notification events
  • Displaying and modifying system parameter default settings
    • System default settings configuration considerations
    • Displaying system parameter default values
    • Modifying system parameter default values
  • Cut-through switching
  • Dynamic buffer allocation for QoS priorities for FastIron X Series devices
    • Default queue depth limits for FastIron X Series devices
    • Configuring the total transmit queue depth limit for FastIron X Series devices
    • Configuring the transmit queue depth limit for a given traffic class on FastIron X Series devices
    • Removing buffer allocation limits on FastIron X Series devices
    • Buffer profile configuration
      • Configuring a buffer profile and defining the queue depth limits
      • Displaying the buffer profile configuration
    • Default queue depth limits for FastIron X Series devices
  • Dynamic buffer allocation for FCX and ICX devices
    • Configuring buffer profiles
      • Configuring buffer profiles with qd-descriptor and qd-buffer commands on FCX and ICX devices
      • Configuring user-configurable buffer profiles on FCX and ICX devices
      • Buffer and descriptor maximum and default allocation values
      • Displaying the user-configurable buffer profile configuration on FCX and ICX devices
    • Configuring buffer sharing on FCX and ICX devices
      • FCX buffer sharing levels
      • ICX 6610 buffer sharing levels
      • ICX 6430 and ICX 6450 buffer sharing levels
      • Displaying buffer sharing information
    • Removing buffer allocation limits on FCX and ICX
    • Buffer profiles for VoIP on FastIron stackable devices
      • Configuring buffer profiles for VoIP
      • Deleting buffer profiles for VoIP
  • Buffer allocation for ICX 6650
    • Buffer and descriptor maximum and default allocation values for ICX 6650
    • ICX 6650 buffer sharing levels
    • Displaying buffer sharing information on ICX 6650
  • Remote Fault Notification on 1Gbps fiber connections
    • Enabling and disabling remote fault notification
  • Link Fault Signaling for 10Gbps Ethernet devices
    • Enabling Link Fault Signaling
    • Viewing the status of LFS-enabled links
  • Jumbo frame support
  • Packet InError Detection
    • Configuring Packet InError Detection
    • Syslog message for error-disabled port due to inError packets
• Metro Features
  • Supported metro features
  • Topology groups
    • Master VLAN and member VLANs
    • Control ports and free ports
    • Topology group configuration considerations
    • Configuring a topology group
    • Displaying topology group information
      • Displaying STP information
      • Displaying topology group information
  • Metro Ring Protocol
    • Metro Ring Protocol configuration notes
    • MRP rings without shared interfaces (MRP Phase 1)
    • MRP rings with shared interfaces (MRP Phase 2)
      • Selection of master node
    • Ring initialization
      • RHP processing in MRP Phase 1
      • RHP processing in MRP Phase 2
    • How ring breaks are detected and healed
    • Master VLANs and customer VLANs
    • Metro Ring Protocol configuration
      • Adding an MRP ring to a VLAN
      • Changing the hello and preforwarding times
    • Metro Ring Protocol diagnostics
      • Enabling MRP diagnostics
      • Displaying MRP diagnostics
    • Displaying MRP information
      • Displaying topology group information
      • Displaying ring information
    • MRP CLI example
      • MRP commands on Switch A (master node)
      • MRP commands on Switch B
      • MRP commands on Switch C
      • MRP commands on Switch D
  • VSRP
    • VSRP configuration notes and feature limitations
    • Layer 2 and Layer 3 redundancy
    • Master election and failover
      • VSRP failover
      • VSRP priority calculation
      • MAC address failover on VSRP-aware devices
      • VSRP interval timers
    • VSRP-aware security features
    • VSRP parameters
    • Configuring basic VSRP parameters
    • Configuring optional VSRP parameters
      • Disabling or re-enabling VSRP
      • Changing the timer scale
      • Configuring authentication
      • Configuring security features on a VSRP-aware device
      • Removing a port from the VRID VLAN
      • Configuring a VRID IP address
      • Changing the backup priority
      • Saving the timer values received from the master
      • Changing the TTL setting
      • Changing the hello interval setting
      • Changing the dead interval setting
      • Changing the backup hello state and interval setting
      • Changing the hold-down interval setting
      • Changing the default track priority setting
      • Specifying a track port setting
      • Disabling or re-enabling backup pre-emption setting
      • Suppressing RIP advertisement from backups
      • VSRP-aware interoperablilty
    • Displaying VSRP information
      • Displaying VRID information
      • Displaying the active interfaces for a VRID
    • VSRP fast start
      • Configuring VSRP fast start
      • Displaying ports that Have the VSRP fast start feature enabled
    • VSRP and MRP signaling
• UDLD and Protected Link Groups
  • Supported UDLD and protected link group features
  • UDLD overview
    • UDLD for tagged ports
    • Configuration notes and feature limitations for UDLD
    • Enabling UDLD
    • Enabling UDLD for tagged ports
    • Changing the Keepalive interval
    • Changing the Keepalive retries
    • Displaying UDLD information
      • Displaying information for all ports
      • Displaying information for a single port
    • Clearing UDLD statistics
  • Protected link groups
    • About active ports
    • Using UDLD with protected link groups
    • UDLD with protected link groups configuration notes
    • Creating a protected link group and assigning an active port
• Link Aggregation
  • Supported link aggregation features
  • Overview of link aggregation
  • LAG formation rules
  • Configuration notes for FastIron devices in a traditional stack
  • Maximum number of LAGs
  • Migrating from a previous release to 08.0.00a LAG or LACP configuration
  • Downgrade considerations
  • LAG Load Sharing
  • LAG hashing on stacking products
    • Removing Layer 2 information from LAG hash output
  • Configuring a LAG
    • Creating a Link Aggregation Group (LAG)
    • Creating a Link Aggregation Group (LAG) using the LAG ID option
      • Configuration considerations
      • Creating a keepalive LAG
      • Adding Ports to a LAG or Deleting Ports from a LAG
      • Configuring the primary port for a LAG
      • Specifying the LAG threshold for a LAG group
      • Configuring an LACP timeout
  • Deploying a LAG
    • Commands available under LAG once it is deployed
    • Disabling ports within a LAG
    • Enabling ports within a LAG
    • Adding a Port to Currently Deployed LAG
    • Deleting a Port from a Currently Deployed LAG
    • Monitoring an individual LAG port
    • Assigning a name to a port within a LAG
      • Allowable characters for LAG names
    • Enabling sFlow forwarding on a port in a LAG
    • Setting the sFlow sampling rate for a port in a LAG
    • IP assignment within a LAG
    • Displaying LAG information
    • Enabling LAG hardware failover
  • Preboot eXecution Environment boot support
    • Enabling PXE boot support on a port
• Multi-Chassis Trunking
  • Supported MCT features
  • Multi-Chassis Trunking Overview
    • How MCT works
    • MCT terminology
    • MCT data flow
    • MCT and VLANs
    • Cluster client automatic configuration
    • MCT feature interaction
    • Basic MCT configuration
      • MCT configuration considerations
      • Differences in configuring MCT for the switch and router image
      • Configuring MCT
        • Step 1: Configure LAG
        • Step 2: Configure the MCT VLAN, MCT session VLAN, and recommended MCT keep-alive VLAN
        • Step 3: Configure the cluster
        • Step 4: Configure clients
    • Setting up cluster client automatic configuration
      • Other cluster client automatic configuration commands
    • MCT failover scenarios
      • Cluster failover mode
      • Client isolation mode
      • Shutting down all client interfaces
      • Using the keep-alive VLAN
      • Setting keep-alive timers and hold-time
  • Layer 2 behavior with MCT
    • MAC operations
      • MAC Database Update
      • Cluster MAC types
      • MAC show commands
      • MAC clear commands
      • Displaying MDUP packet statistics
      • Syncing router MAC addresses to peer MCT devices
      • Dynamic trunks
    • Port loop detection
    • MCT Layer 2 protocols
      • MRP
      • STP/RSTP
      • BPDU forwarding
    • Protocol-based VLANs
    • Uplink switch
    • Layer 2 multicast snooping over MCT
      • IGMP/MLD snooping
      • IGMP/MLD snooping behavior on MCT cluster devices
      • How failovers are handled for Layer 2 multicast over MCT
      • PIM-SM and PIM6-SM snooping over MCT
      • Forwarding entries for PIM-SM and PIM6-SM multicast snooping
    • Forcing a port up in a basic MCT configuration
  • Layer 3 behavior with MCT
    • Layer 3 unicast over MCT
      • Device A
      • Device B
      • Switch S1
    • MCT for VRRP or VRRP-E
      • Layer 3 traffic forwarding from CEPs to CCEPs
      • Layer 3 traffic forwarding from CCEPs to CEPs
      • ARP resolution
      • VRRP or VRRP-E configuration with MCT
      • VRRP-E short-path forwarding and revertible option
  • Displaying MCT information
    • Displaying peer and client states
    • Displaying state machine information
    • Displaying cluster, peer, and client states
    • Displaying information about Ethernet interfaces
    • Displaying STP information
    • Displaying information for multicast snooping
  • MCT configuration examples
    • Single-level MCT example
      • Client 1 - Configuration
      • Client 2- Configuration
      • AGG-A (R1) - Configuration
      • AGG-B (R2) - Configuration
    • Two-level MCT example
      • AGG-A (R1) - Configuration
      • AGG-B (R2) - Configuration
      • DIST-A (R3) - Configuration
      • DIST-B (R4) - Configuration
    • MCT configuration with VRRP-E example
      • SX800A - MCT configuration
      • SX800A - VRRP-E configuration
      • SX800B- MCT configuration
      • SX800B - VRRP-E configuration
      • S1-SW configuration
    • Multicast snooping configuration example
    • MCT configuration examples using STP
      • Example 1: Configure the Per-VLAN Spanning Tree on the MCT Clients
      • Example 2: Configure Single Spanning Tree (SSTP) on the MCT Clients
      • Example 3: Configure Multiple Spanning Tree (MSTP) on the MCT Clients
• GVRP
  • Supported GVRP features
  • GVRP overview
  • GVRP application examples
    • Dynamic core and fixed edge
    • Dynamic core and dynamic edge
    • Fixed core and dynamic edge
    • Fixed core and fixed edge
  • VLAN names created by GVRP
  • Configuration notes for GVRP
  • GVRP configuration
    • Changing the GVRP base VLAN ID
    • Increasing the maximum configurable value of the Leaveall timer
    • Enabling GVRP
    • Disabling VLAN advertising
    • Disabling VLAN learning
    • Changing the GVRP timers
      • Timer configuration requirements
      • Changing the Join, Leave, and Leaveall timers
      • Resetting the timers to their defaults
  • Converting a VLAN created by GVRP into a statically-configured VLAN
  • Displaying GVRP information
    • Displaying GVRP configuration information
    • Displaying GVRP VLAN information
    • Displaying GVRP statistics
  • Clearing GVRP statistics
  • GVRP CLI examples
    • Dynamic core and fixed edge
    • Dynamic core and dynamic edge
    • Fixed core and dynamic edge
    • Fixed core and fixed edge
• Port mirroring and Monitoring
  • Supported port mirroring and monitoring features
  • Port mirroring and monitoring overview
  • Port mirroring and monitoring configuration
    • Configuration notes for port mirroring and monitoring
    • Command syntax for port mirroring and monitoring
      • Monitoring a port
      • Monitoring an individual LAG port
  • Mirroring configuration on a traditional stack
    • Configuration notes for traditional stack mirroring
      • Configuring mirroring for ports on different members in a traditional stack example
      • Configuring mirroring for ports on the same stack member in a traditional stack example
  • ACL-based inbound mirroring
    • Creating an ACL-based inbound mirror clause for FCX and ICX devices
    • ACL-based inbound mirror clauses for FastIron X Series devices
    • Destination mirror port
      • Specifying the destination mirror port for physical ports
      • Specifying the destination mirror port for trunk ports
      • Configuring ACL-based mirroring for ACLs bound to virtual interfaces
  • MAC address filter-based mirroring
    • Configuring MAC address filter-based mirroring
      • 1. Defining a mirror port
      • 2. Creating a MAC address filter with a mirroring clause
      • 3. Applying the MAC address filter to an interface
      • 4. Configuring the monitor port to use the mirror port
  • VLAN-based mirroring
    • Configuring VLAN-based mirroring
    • Displaying VLAN-based mirroring status
    • Configuration notes for VLAN-based mirroring
    • VLAN-based mirroring
      • Restrictions and capabilities of VLAN-based mirroring
      • Tagged versus untagged ports in VLANs
      • Configuring VLAN-based mirroring
      • Displaying VLAN-based mirroring status
• Spanning Tree Protocol
  • Supported STP features
  • STP overview
  • Standard STP parameter configuration
    • STP parameters and defaults
    • Enabling or disabling the Spanning Tree Protocol (STP)
      • Enabling or disabling STP globally
      • Enabling or disabling STP in a port-based VLAN
      • Enabling or disabling STP on an individual port
    • Changing STP bridge and port parameters
      • Changing STP bridge parameters
      • Changing STP port parameters
    • STP protection enhancement
      • Enabling STP protection
      • Clearing BPDU drop counters
      • Viewing the STP Protection Configuration
    • Displaying STP information
      • Displaying STP information for an entire device
      • Displaying the STP state of a port-based VLAN
      • Displaying detailed STP information for a single port in a specific VLAN
      • Displaying STP state information for an individual interface
  • STP feature configuration
    • Fast port span
      • Disabling and re-enabling fast port span
      • Excluding specific ports from fast port span
    • Fast Uplink Span
      • Active uplink port failure
      • Switchover to the active uplink port
      • Fast Uplink Span Rules for Trunk Groups
      • Configuring a Fast Uplink Port Group
      • Configuring Fast Uplink Span within a VLAN
    • 802.1W Rapid Spanning Tree (RSTP)
      • Bridges and bridge port roles
      • Edge ports and edge port roles
      • Point-to-point ports
      • Bridge port states
      • Edge port and non-edge port states
      • Changes to port roles and states
      • 802.1W convergence in a simple topology
      • Convergence after a link failure
      • Convergence at link restoration
      • Convergence in a complex 802.1W topology
      • Propagation of topology change
      • Compatibility of 802.1W with 802.1D
      • Configuring 802.1W parameters on a Brocade device
      • Displaying information about 802-1W
    • 802.1W Draft 3
      • Spanning tree reconvergence time
      • 802.1W configuration considerations
      • Enabling 802.1W Draft 3
    • Single Spanning Tree (SSTP)
      • SSTP defaults
      • Enabling SSTP
      • Displaying SSTP information
    • STP per VLAN group
      • STP load balancing
      • Configuring STP per VLAN group
      • Configuration example for STP load sharing
  • PVST/PVST+ compatibility
    • Overview of PVST and PVST+
    • VLAN tags and dual mode
    • Configuring PVST+ support
      • Enabling PVST+ support manually
      • Enabling dual-mode support
    • Displaying PVST+ support information
    • PVST+ configuration examples
      • Tagged port using default VLAN 1 as its port native VLAN
      • Untagged port using VLAN 2 as port native VLAN
  • PVRST compatibility
  • BPDU guard
    • Enabling BPDU protection by port
    • Re-enabling ports disabled by BPDU guard
    • Displaying the BPDU guard status
      • BPDU guard status example configurations
    • BPDU guard status example console messages
  • Root guard
    • Enabling STP root guard
    • Displaying the STP root guard
    • Displaying the root guard by VLAN
  • Designated Protection
    • Enabling Designated Protection on a port
    • Syslog message for a port in designated inconsistent state
  • Error disable recovery
    • Enabling an error-disabled port automatically
    • Enabling an error-disabled port manually
    • Setting the recovery interval
    • Displaying the error disable recovery state by interface
    • Displaying the recovery state for all conditions
    • Displaying the recovery state by port number and cause
    • Errdisable Syslog messages
  • 802.1s Multiple Spanning Tree Protocol
    • Multiple spanning-tree regions
    • Configuration notes
    • Configuring MSTP mode and scope
    • Reduced occurrences of MSTP reconvergence
      • Example application of MSTP reconvergence
      • Deleting a VLAN to MSTI mapping
      • Viewing the MSTP configuration digest
    • Configuring additional MSTP parameters
      • Setting the MSTP name
      • Setting the MSTP revision number
      • Configuring an MSTP instance
      • Configuring bridge priority for an MSTP instance
      • Setting the MSTP global parameters
      • Setting ports to be operational edge ports
      • Setting automatic operational edge ports
      • Setting point-to-point link
      • Disabling MSTP on a port
      • Forcing ports to transmit an MSTP BPDU
      • Displaying MSTP statistics
      • Displaying MSTP information for a specified instance
      • Displaying MSTP information for CIST instance 0
• VLANs
  • Supported VLAN features
  • VLAN overview
    • Types of VLANs
      • VLAN support on FastIron devices
      • Layer 2 port-based VLANs
      • Configuring port-based VLANs on FSX-A
      • Configuring port-based VLANs on FSX-B
      • Configuring port-based VLANs on FSX-C
    • Modifying a port-based VLAN
      • Removing a port-based VLAN
      • Removing a port from a VLAN
      • Multi-range VLAN
      • Layer 3 protocol-based VLANs
      • Integrated Switch Routing (ISR)
      • IP subnet, IPX network, and AppleTalk cable VLANs
    • Default VLAN
    • 802.1Q tagging
      • Support for 802.1ad (Q-in-Q) tagging
    • Spanning Tree Protocol (STP)
    • Virtual routing interfaces
    • VLAN and virtual routing interface groups
    • Dynamic, static, and excluded port membership
      • Dynamic ports
      • Static ports
      • Excluded ports
      • Broadcast leaks
    • Super aggregated VLANs
    • Trunk group ports and VLAN membership
    • Summary of VLAN configuration rules
      • Multiple VLAN membership rules
  • Routing between VLANs
    • Virtual routing interfaces (Layer 2 Switches only)
    • Routing between VLANs using virtual routing interfaces (Layer 3 Switches only)
    • Dynamic port assignment (Layer 2 Switches and Layer 3 Switches)
    • Assigning a different VLAN ID to the default VLAN
    • Assigning different VLAN IDs to reserved VLANs 4091 and 4092
      • Viewing reassigned VLAN IDs for reserved VLANs 4091 and 4092
    • Assigning trunk group ports
    • Enable spanning tree on a VLAN
  • Configuring IP subnet, IPX network and protocol-based VLANs
    • IP subnet, IPX network, and protocol-based VLAN configuration example
  • IP subnet, IPX network, and protocol-based VLANs within port-based VLANs
    • Configuring Layer 3 VLANs on FSX-A
    • Configuring Layer 3 VLANs on FSX-B
    • Configuring Layer 3 VLANs on FSX-C
  • IPv6 protocol VLAN configuration
  • Routing between VLANs using virtual routing interfaces (Layer 3 Switches only)
    • Configuring Layer 3 VLANs and virtual routing interfaces on the FSX-A
    • Configuring Layer 3 VLANs and virtual routing interfaces for FSX-B
    • Configuring Layer 3 VLANs and virtual routing interfaces for FSX-C
  • Configuring protocol VLANs with dynamic ports
    • Aging of dynamic ports
      • Disabling membership aging of dynamic VLAN ports
    • Configuration guidelines for membership aging of dynamic VLAN ports
    • Configuring an IP, IPX, or AppleTalk Protocol VLAN with Dynamic Ports
    • Configuring an IP subnet VLAN with dynamic ports
    • Configuring an IPX network VLAN with dynamic ports
  • Configuring uplink ports within a port-based VLAN
    • Configuration considerations for uplink ports within a port-based VLAN
    • Configuration syntax for uplink ports within a port-based VLAN
  • IP subnet address on multiple port-based VLANconfiguration
  • VLAN groups and virtual routing interface group
    • Configuring a VLAN group
      • Displaying information about VLAN groups
    • Configuring a virtual routing interface group
      • Configuration notes and feature limitations for virtual routing interface group
      • CLI syntax for virtual routing interface group
    • Displaying the VLAN group and virtual routing interface group information
    • Allocating memory for more VLANs or virtual routing interfaces
      • Increasing the number of VLANs you can configure
      • Increasing the number of virtual routing interfaces you can configure
  • Super-aggregated VLAN configuration
    • Configuration notes for aggregated VLANs
    • Configuring aggregated VLANs
      • Configuring aggregated VLANs on an edge device
      • Configuring aggregated VLANs on a core device
    • Verifying the aggregated VLAN configuration
    • Complete CLI examples for aggregated VLANs
      • Commands for configuring aggregated VLANs on device A
      • Commands for configuring aggregated VLANs on device B
      • Commands for configuring aggregated VLANs on device C
      • Commands for configuring aggregated VLANs on device D
      • Commands for configuring aggregated VLANs on device E
      • Commands for configuring aggregated VLANs on device F
  • 802.1ad tagging configuration
    • Configuration rules for 802.1ad tagging
    • Enabling 802.1ad tagging
    • Example 802.1ad configuration
    • Configuring 802.1ad tag profiles
      • Configuration notes for 802.1ad tagging
      • CLI Syntax for 802.1ad tagging
  • Private VLAN configuration
    • Configuration notes for PVLANs and standard VLANs
      • Configuring the primary VLAN
      • Configuring an isolated or community PVLAN
    • Enabling broadcast or unknown unicast traffic to the PVLAN on FSX devices
    • CLI example for a general PVLAN network
    • CLI example for a PVLAN network with switch-switch link ports
    • Multiple promiscuous ports support in private VLANs
      • Mapping secondary VLAN to primary VLAN by multiple promiscuous ports
  • Dual-mode VLAN ports
  • Displaying VLAN information
    • Displaying VLANs in alphanumeric order
    • Displaying system-wide VLAN information
    • Displaying global VLAN information
    • Displaying VLAN information for specific ports
    • Displaying a port VLAN membership
    • Displaying a port dual-mode VLAN membership
    • Displaying port default VLAN IDs (PVIDs)
    • Displaying PVLAN information
• VXLAN
  • Supported VXLAN features
  • VXLAN gateway overview
  • Inner frame VLAN tagging
  • Load balancing entropy
  • MAC learning
  • Quality of Service support
  • Unsupported features
  • VXLAN configuration considerations
  • Configuring VXLAN
• VXLAN-related syslog messages
• Layer 2 Commands
  • clear notification-mac statistics
  • errdisable packet-inerror-detect
  • failover
  • force-up ethernet
  • interface l2-tunnel
  • l2-tunnel
  • l2-tunnel mode vxlan eline
  • mac-notification interval
  • packet-inerror-detect
  • show interface l2-tunnel
  • show notification-mac
  • show packet-inerror-detect
  • show span designated-protect
  • snmp-server enable traps mac-notification
  • spanning-tree designated-protect
  • system-max mac-notification-buffer
  • vxlan vlan