Extreme SLX-OS Layer 2 Switching Configuration Guide, 20.7.2
> Loop Detection
Extreme Networks, Inc. July 15, 2025
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Supported Hardware
Regarding Ethernet interfaces and chassis devices
Link Aggregation
Link aggregation overview
LAG configuration guidelines
LAG profile support-scope
Basic LAG configuration
Configuring a new port channel interface
Deleting a port channel interface
Adding a member port to a port channel
Deleting a member port from a port channel
Configuring the minimum number of LAG member links
Dynamic (LACP) configuration
Configuring LACP system priority
Configuring the LACP port priority
Configuring the LACP timeout period
LACP PDU forwarding
Configuring LACP PDU forwarding on a physical interface
Configuring LACP PDU forwarding on a port-channel interface
Configuring LACP default Up
IP over port-channel
Hash-based Load Balancing
Configuring LAG Hashing
Configuring header protocols for load-balancing
Load balancing mechanism on different traffic types
Load balance hash support on different devices
LAG hash support on different devices
MPLS transit load balancing
Troubleshooting LAGs
Show and clear LAG commands
Displaying port-channel information
Displaying LAG hashing
Displaying LACP system-id information
Displaying LACP statistics
Clearing LACP counter statistics on a LAG
Clearing LACP counter statistics on all LAG groups
VLANs
802.1Q VLAN overview
Configuring VLANs
Configuring a VLAN
Configuring a switchport interface
Configuring the switchport interface mode
Configuring the switchport access VLAN type
Configuring a VLAN in trunk mode
Configuring a native VLAN on a trunk port
Enabling VLAN tagging for native traffic
Displaying the status of a switchport interface
Displaying the switchport interface type
Verifying a switchport interface running configuration
Displaying VLAN information
Enabling Layer 3 routing for VLANs
VLAN statistics
Enabling statistics on a VLAN
Displaying statistics for VLANs
Clearing statistics on VLANs
VE route-only mode
Configuring VE route-only mode on a physical port
Configuring VE route-only mode on a LAG port
VxLAN Layer 2 Gateway
VxLAN Layer 2 gateway overview
VxLAN Layer 2 gateway considerations and limitations
Configuring VxLAN Layer 2 gateway
VxLAN Layer 2 gateway support for bridge domains
Configuring VxLAN Layer 2 Gateway support for bridge domains
VxLAN Layer 2 gateway payload tag processing
VxLAN Layer 2 support for LVTEP
LVTEP control plane
LVTEP data plane
Port-based VLAN bundle service
Configuring VxLAN LVTEP support
LVTEP support for other features
Nondefault TPID
Configuring a nondefault TPID
Configuring TCAM profiles to support LVTEP
LVTEP show commands
QoS for VxLAN Layer 2 gateways
Multiple VLAN Registration Protocol (MVRP)
Multiple VLAN Registration Protocol overview
MVRP considerations and limitations
Enabling MVRP on an Ethernet interface
Configuring an edge port
Configuring the VLAN registration mode on the interface
MVRP over a port channel
Enabling MVRP over a port channel
Configuring the MVRP join, leave, and leave-all timers
Displaying MVRP configuration information, statistics, and attributes
Clearing MVRP statistics
Multi-Chassis Trunking (MCT)
MCT Overview
MCT terminology
SLX-OS MCT control plane
Inter-Chassis Link for the SLX Devices
Designated Forwarder Election
MCT Data Plane for the SLX Devices
Forwarding unicast traffic
Flooding traffic from a CEP
Flooding traffic received from the CCEP
SLX_mct_data_plane_uni_CEP_CCEP
MAC management
Static MAC handling
MAC learning
MAC aging rules
MAC movement
MAC address deletion
MCT configuration considerations
Configuring MCT
Configuring additional MCT cluster parameters
Displaying MCT information
Displaying the cluster information
Displaying the cluster client information
Displaying member VLAN information
Displaying and clearing the MAC address table cluster information
VPLS and VLL MCT on the SLX 9640 and 9540 devices
Control plane for VPLS or VLL MCT
PW redundancy for VPLS and VLL MCT
PW state in VPLS or VLL MCT
VLL-MCT data plane
VPLS-MCT data plane
VPLS MCT BUM traffic
VPLS-MCT PE node protection
VPLS MAC Management
VPLS MAC movement
MAC address deletion
Configuration Considerations and Limitations for VPLS and VLL MCT
Configuring MCT for VPLS or VLL
Displaying information related to VPLS and VLL MCT
Layer 3 routing over MCT
Using MCT with VRRP and VRRP-E
MCT Use Cases
L2 MCT in the data center core
L2 MCT in a data center with a collapsed core and aggregation
Logical Interfaces
Logical interfaces overview
Configuring a logical interface on a physical port or port-channel (LAG)
Bridge Domains
Bridge domain overview
Bridge domain statistics
Configuring a bridge domain
Displaying bridge-domain configuration information
Enabling statistics on a bridge domain
Displaying statistics for logical interfaces in bridge domains
Clearing statistics on bridge domains
VPLS and VLL Layer 2 VPN services
VPLS overview
VLL
VPLS service endpoints
Local switching
Pseudowires
Pseudowire operation
Supported pseudowire features
Unsupported pseudowire features
VLAN tag manipulation (vc-mode) on pseudowires
PW statistics
Pseudowire control word and flow label
Supported VPLS features
Configuration of VPLS and VLL
QoS treatment in VPLS packet flow
Configuring a PW profile
Attaching a PW profile to a bridge domain
Configuring control word for a PW profile
Configuring PW control word on a bridge domain
Configuring flow label for a PW profile
Configuring PW flow label on a bridge domain
Configuring a static MAC address over an endpoint in a VPLS instance
Displaying MAC address information for VPLS bridge domains
Configuring a VPLS instance
Configuring a VLL instance
Routing VE over VPLS
Configuration example for VPLS with switching between ACs and network core
SLX-OS_VPLS_topology
VPLS MAC withdrawal
Enabling VPLS MAC address withdrawal
MAC Movement Detection and Resolution
MAC Movement Overview
MAC Movement Detection
MAC Movement Resolution
MAC movement Detection and Resolution Commands
802.1ag Connectivity Fault Management
Enabling or disabling CFM
Creating a Maintenance Domain
Creating and configuring a Maintenance Association
Displaying CFM configurations
show cfm
show cfm connectivity
show cfm brief
802.1d Spanning Tree Protocol
Spanning Tree Protocol overview
Spanning Tree Protocol configuration notes
STP states
BPDUs
TCN BPDUs
STP configuration guidelines and restrictions
Understanding the default STP configuration
STP features
Root guard
BPDU guard
Error disable recovery
PortFast
STP parameters
Bridge parameters
Error disable timeout parameter
Port-channel path cost parameter
Configuring STP
Enabling and configuring STP globally
Enabling and configuring STP on an interface
Configuring basic STP parameters
Re-enabling an error-disabled port automatically
Clearing spanning tree counters
Clearing spanning tree-detected protocols
Shutting down STP
802.1w Rapid Spanning Tree Protocol
Rapid Spanning Tree Protocol overview
RSTP Parameters
Edge port and automatic edge detection
Configuring RSTP
Enabling and configuring RSTP globally
Enabling and configuring RSTP on an interface
Configuring basic RSTP parameters
Clearing spanning tree counters
Clearing spanning tree-detected protocols
Shutting down RSTP
Per-VLAN Spanning Tree+ and Rapid Per-VLAN Spanning Tree+
PVST+ and R-PVST+ overview
Bridge protocol data units in different VLANs
BPDU configuration notes
BPDU R-PVST+ header and field comparisons
Sent BPDUs
TCN headers and fields
PortFast
Edge port and automatic edge detection
Configuring PVST+ and R-PVST+
Enabling and configuring PVST+ globally
Enabling and configuring PVST+ on an interface
Enabling and configuring PVST+ on a system
Enabling and configuring R-PVST+ globally
Enabling and configuring R-PVST+ on an interface
Enabling and configuring R-PVST+ on a system
Clearing spanning tree counters
Clearing spanning tree-detected protocols
Shutting down PVST+ or R-PVST+
802.1s Multiple Spanning Tree Protocol
MSTP overview
MSTP guidelines and restrictions
Interoperability with PVST+ and R-PVST+
MSTP global level parameters
MSTP interface level parameters
Edge port and automatic edge detection
BPDU guard
Restricted role
Restricted TCN
Configuring MSTP
Enabling and configuring MSTP globally
Enabling and configuring MSTP on an interface
Enabling MSTP on a VLAN
Configuring basic MSTP parameters
Clearing spanning tree counters
Clearing spanning tree-detected protocols
Shutting down MSTP
Topology Groups
Topology Groups
Master VLAN, member VLANs, and bridge-domains
Control ports and free ports
Configuration considerations
Configuring a topology group
Configuring a master VLAN
Adding member VLANs
Adding member bridge-domains
Replacing a master VLAN
Displaying topology group information
Loop Detection
LD protocol overview
LD use cases
MCT strict mode
MCT loose mode
Configuring LD protocol
Loop detection for VLAN
Configuring loop detection for VLAN
Ethernet Ring Protection Protocol
Ethernet Ring Protection overview
ERP components
ERN roles
ERN interfaces
Protocols
Using standalone ERP
Using ERP with IEEE 802.1ag support
ERP messaging
ERP operational states
ERP timers
Initializing a new ERN
Signal Fail
Manual Switch
Forced Switch
Double Forced Switch
Dual-end blocking
Non-revertive mode
Interconnected rings
Configuring ERP
ERP topology and configuration
Assigning ERP IDs
Naming an Ethernet Ring Node
Configuring the default MAC ID
Configuring a R-APS MEL value
Configuring R-APS topology change propagation
Configuring interfaces
Enabling the ERP configuration
Assigning the RPL owner role and setting the RPL
Enabling sub-rings for multi-ring and ladder topologies
Configuring non-revertive mode
Configuring and clearing a forced switch
Configuring and clearing a manual switch
Configuring the guard timer
Configuring and clearing the WTR timer
Testing the WTR timer
Configuring and clearing the WTB timer
Configuring a hold-off timer
Setting the ITU-T G.8032 version number
Configuring ERP with IEEE 802.1ag
ETH-CSF
ETH-CSF overview
ETH-CSF use case
ETH-CSF specifications
ETH-CSF and port-channel
CSF transmission
CSF reception
ETH-CSF PDU structure
ETH-CSF considerations and limitations
Configuring ETH-CSF
Loop Detection
Section contents:
LD protocol overview
The loop detection (LD) protocol is an
Extreme Networks
proprietary protocol used to detect and break Layer 2 loops caused by misconfigurations, thereby preventing packet storms.
LD use cases
In an MCT configuration, LD runs independently on both nodes. With loose mode the user must enable loop detection for the same VLANs on both nodes in the MCT cluster. MCT strict mode and loose mode use cases are detailed below.
Configuring LD protocol
Follow these steps to configure loop detection (LD) protocol globally and at the interface and VLAN level.
Loop detection for VLAN
LD loose mode is used to support a shutdown at the attachment circuit (AC) logical interface (LIF) level instead of at the physical port level.
