Extreme SLX-OS MPLS Configuration Guide, 20.7.2
> Label Distribution Protocol
Extreme Networks, Inc. July 15, 2025
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Preface
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About This Document
What's New in this Document
Supported Hardware
MPLS Traffic Engineering
MPLS Traffic Engineering Overview
IETF RFC and Internet Draft Support
How MPLS Works
How Packets are Forwarded Through an MPLS Domain
MPLS Label Header Encoding
Traffic-Engineered LSPs
CSPF Calculates a Traffic-Engineered Path
Penultimate Hop Popping
MPLS CSPF Fate-Sharing Group
Configuration Considerations When Using CSPF Fate-Sharing Group Information
Configure an MPLS CSPF Fate-Sharing Group
Delete CSPF Groups
Display CSPF Fate-Sharing Group Configuration
IS-IS Link State Protocol Data Units with TE Extensions for MPLS Interfaces
Configure MPLS
Enable MPLS
MPLS over Virtual Ethernet Interfaces
Configuration Considerations before Enabling MPLS on a VE Interface
Enable MPLS on a LAG Interface
Configuration Considerations for Enabling MPLS on a LAG Interface
Set Global MPLS Policy Parameters
Set the Retry Limit
Set the Retry Time
Establish Administrative Group Names
Enable IS-IS LSPs with TE Extensions for MPLS Interfaces
Display Information about IS-IS LSPs with TE Extensions
Configure CSPF Interface Constraint
Set Traffic Engineering Parameters for MPLS Interfaces
Reserve Bandwidth on an Interface
Reservable Bandwidth Configuration Considerations
Configure the Maximum Reservable Bandwidth
Configure the Maximum Reservable Bandwidth as a Percentage
Configuration Considerations
Add Interfaces to Administrative Groups
MPLS Process Restart
Traffic Engineering Database
LSP Attributes and Requirements Used for Traffic Engineering
Calculating a Path Based on an Interface Address
How RSVP Establishes a Signaled LSP
Refresh Messages
Admission Control, Bandwidth Allocation, and LSP Preemption
Admission Control
Bandwidth Allocation
LSP Preemption
MPLS Traffic Engineering Flooding Reduction
MPLS Traffic Engineering Flooding Reduction Global Configuration
MPLS Traffic Engineering Flooding Reduction Interface Specific Configuration
Configure the Periodic Flooding Timer
RSVP Soft Preemption
Configure RSVP Soft Preemption
Soft-preemption Cleanup-timer
RASLOG Messages
Path Selection Metric for CSPF Computation
Configure the CSPF Computation Mode
Path Selection for CSPF Computation
Configure the CSPF Computation Mode Value at Global Level
Configure TE-metric for an Interface
Configure TE-Metric for MPLS Interface
Configure the CSPF Computation Mode Value for Primary LSPs
Global RSVP parameters
RSVP message authentication
Configuring RSVP Message Authentication
RSVP reliable messaging
Configuring RSVP Reliable Messaging
RSVP refresh reduction
Configuring RSVP Bundle Messages
Configuring RSVP Summary Refresh
Displaying Refresh Reduction Information for an Interface
RSVP Message Authentication on an MPLS VE Interface
Configuring RSVP Message Authentication on an MPLS VE Interface
Displaying MPLS and RSVP Information
RSVP IGP Synchronization
Configuring RSVP IGP synchronization
RSVP IGP synchronization for remote links
Types of LSPs
Signaled LSPs
Setting up Signaled LSPs
Setting up Paths
Modifying a Path
Inserting a Hop into a Path
Deleting a Path
Configuring Signaled LSP Parameters
Resetting LSPs
Resetting Normal LSPs
Reset LSP Considerations
MPLS Bypass LSP
MPLS Facility Backup FRR
Bypass LSP
Adaptive Bypass LSP
Best Bypass LSP Selection
Liberal Bypass LSP Selection
CSPF group penalty for backup path
FRR LSP switch to backup path on bypass LSP
Configuring a static bypass LSP
Enabling and disabling a bypass LSP
Configuring a bypass LSP adaptive parameter
Configuring Bypass LSP Exclude Interface
Configuring bypass LSP to address
Configuring bypass LSP from address
Configuring a bypass LSP record route
Configuring a bypass LSP CSPF computation mode
Configuring a bypass LSP CSPF tie breaking option
Configuring bypass LSP CoS parameter
Configuring a bypass LSP hop limit
Configuring bypass LSP priority values
Configuring bypass LSP bandwidth parameters
Configuring a bypass LSP re-optimization timer
Configuring a bypass LSP primary path
Committing adaptive parameters of a bypass LSP
Dynamic Bypass LSP
Dynamic bypass LSP creation
Dynamic bypass naming
Deletion of dynamic bypass LSPs
Dynamic bypass configurations
Dynamic bypass global configuration
Globally enabling a dynamic bypass
Disabling global dynamic bypass
Enabling dynamic bypass on all interfaces
Setting the maximum number of dynamic bypass LSPs
Setting the Maximum Number of Dynamic Bypass LSPs per Merge Point
Setting the reoptimizer-timer
Configuring Adaptiveness to Dynamic Bypass LSPs
Configuring Administrative Groups
Dynamic bypass interface configurations
Enabling Dynamic Bypass on an MPLS Interface
Disabling Dynamic Bypass on MPLS Interfaces
Setting the Maximum Number of Dynamic Bypasses per Interface
Setting the Maximum Number of Dynamic Bypass LSPs per Merge Point
Specifying the Name Prefix
Setting the Priority
Enabling and Disabling the Record Route Option
Setting Traffic Engineering Bandwidth Parameters
Setting Tie-Break Option for Dynamic Bypass CSPF
Setting the Hop Limit for Dynamic Bypass CSPF
Setting CoS for Dynamic Bypass LSPs
Setting the From-Address for Dynamic Bypass LSPs
Setting the Explicit Path for Dynamic Bypass LSPs
Setting CSPF Computation Mode for Dynamic Bypass LSPs
Bypass LSP RSVP IGP Synchronization
Bypass LSP Statistics
Link Protection for FRR
Configuring an Adaptive LSP
Re-optimizing LSPs
Time-triggered re-optimizing
RSVP LSP with FRR
RSVP Per-Session Statistics
RSVP Per-Session Statistics and their Applicability
RSVP-TE Hello
RSVP-TE Hello Extension Composition
RSVP-TE Hello Process
RSVP-TE Hello Considerations
Create an LSP
Specifying the Egress LER
Specifying a source address for an LSP
Configuring Redundant Paths for an LSP
Configuring Path Selection
Configuring a Path Selection Revert Timer
Usage Considerations:
Specifying the Primary Path for an LSP
Configuring Signaled LSP Parameters
Performing a Commit for an LSP Configuration Command
Performing an Explicit Commit
Performing an Implicit Commit
Setting a Class of Service Value for the LSP
Allocating Bandwidth to an LSP
Configuring a Priority for a Signaled LSP
Assigning a Metric to the LSP
Including or Excluding Administrative Groups from LSP Calculations
Limiting the Number of Hops the LSP Can Traverse
Specifying a Tie-Breaker for Selecting CSPF Equal-Cost Paths
Disabling CSPF Path Calculations
Disabling the Record Route Function
Configuring the Maximum Packet Size
Enabling a Signaled LSP
Disabling a Signaled LSP
Configuring the RSVP Refresh Interval
Configuring the RSVP refresh multiple
Displaying MPLS
Displaying the Traffic Engineering database
Displaying a traffic engineering path to a destination
Displaying signaled LSP status information
Displaying path information
Displaying the MPLS routing table
Displaying the MPLS forwarding information
Displaying MPLS configuration information
Displaying in the detail mode
Displaying filtered MPLS configuration information
Displaying RSVP information
Displaying the status of RSVP interfaces
Displaying RSVP protocol packet statistics
Displaying the RSVP version
MPLS traffic statistics
Counter Profiles
MPLS Traffic Statistics Data Streaming
Configuring telemetry streaming for MPLS traffic data
Tunnel statistics
Ingress tunnel accounting
Configuring ingress tunnel accounting
Displaying MPLS tunnel statistics
Clearing MPLS tunnel statistics
Configuring transit session accounting
Displaying MPLS transit statistics
Clearing MPLS transit statistics
Adaptive Fast Reroute (FRR) and Global Revertiveness
Configuring FRR on an LSP to be adaptive
Global Revertiveness
Global revertiveness configuration
Changing FRR bandwidth for an adaptive LSP
Setting the revertive hold time
Global revertiveness configurations
Changing FRR bandwidth for an adaptive LSP
Adaptive LSP configuration
Displaying global revertiveness information
MPLS over Virtual Ethernet Interfaces
Displaying MPLS configuration information for a VE interface
MPLS enabled interface
Example of MPLS Fast Reroute Configuration
Displaying RSVP session information for example network
The Transit Router 1 display
The Ingress Router 4 display
The Transit Router 2 display
The Transit Router 3 display
The Egress Router 5 display
The Transit Router 6 display
Configuring MPLS fast reroute using one-to-one backup
Configuring MPLS fast reroute using one-to-one backup
Configuring bandwidth for a MPLS fast reroute
Configuring priority for a MPLS fast reroute
MPLS OAM
Ping MPLS RSVP LSP
Traceroute MPLS RSVP LSP
Ping MPLS LDP Tunnel
Traceroute MPLS LDP Tunnel
Auto-Bandwidth
Auto-bandwidth components
Configurable table-based absolute adjustment-threshold
Underflow-limit
Sample-history
Configuring the threshold-table for adjustment threshold
Configuring the underflow limit
Displaying the sample-history
Special circumstance behaviors
Label Distribution Protocol
LDP overview
LDP terminology
Configuring LDP on an Interface
Configuring the LDP session keepalive interval
Configuring the LDP session keepalive timeout
LDP Hello interval and Hello Hold timeout timers
LDP Hello interval
LDP Hello Hold time
Changing the LDP Hello Interval
Changing the LDP Hold Time Sent to Adjacent LSRs
Configuring LDP message authentication
Resetting LDP neighbors
Validating LDP session reset
LDP route injection
Considerations when using LDP route injection
Configuring LDP route injection
LDP route injection example
LDP inbound-FEC filtering
Configuration considerations for LDP inbound-FEC filtering
Configuring LDP inbound FEC filtering
Displaying inbound FEC filter information
FEC Filtering Configuration Example
LDP outbound FEC filtering
Configuring global LDP outbound FEC filtering
Configuring neighbor-based LDP outbound FEC filtering
Label withdrawal delay timer
Label Withdrawal Delay at Ingress
Label Withdrawal Delay and LDP Graceful Restart
Label withdrawal delay and LDP-IGP synchronization
Configuring the label withdrawal delay timer
LDP ECMP for transit LSR
Changing the maximum number of LDP ECMP paths
MPLS LDP-IGP Synchronization
LDP-IGP synchronization hold-down time
Configuring LDP-IGP synchronization
Configuring MPLS LDP-IGP synchronization and hold time globally
Enabling MPLS LDP-IGP Synchronization on an Interface
Configuring the receive label silence and EOL timers for LDP-IGP synchronization
Displaying LDP-IGP synchronization information
LDP Graceful Restart
LSR restarting procedure
GR helper LSR restarting procedure
Graceful restart scenarios
Ingress LSR specific processing
Transit LSR specific processing
Configuring LDP graceful restart (GR)
Configurable LDP router ID
Configuring the LDP router ID
Displaying LDP information and statistics
Configuration Example of LDP-Enabled LSRs
IP over MPLS
BGP shortcuts using next-hop MPLS
Cost of a BGP shortcut using next-hop MPLS
LSP with a fixed metric of one when next-hop is enabled
LSP metric comparison when next-hop MPLS is enabled
Follow-IGP metrics when next-hop MPLS is enabled
Configuring BGP shortcuts using next-hop MPLS
Configuring BGP shortcuts using next-hop MPLS with Follow-IGP metrics
ECMP forwarding for IP over MPLS
QoS mapping between IP packets and MPLS
Configuring QoS mapping between IP packets and MPLS through an LSP
IP-over-MPLS QoS TTL propagation control
Changing the MPLS QoS mode
BGP or MPLS VPNs
What is a BGP or MPLS VPN
IETF RFC and Internet Draft Support
BGP or MPLS VPN components and what they do
BGP or MPLS VPN operation
Creating Routes in a BGP or MPLS VPN
Routing a Packet through a BGP or MPLS VPN
L3VPN Over MPLS Tunnel
Configuring BGP or MPLS VPNs on a PE
Defining a VRF routing instance
Assigning a Route Distinguisher to a VRF
Defining IPv4 or IPv6 address families of a VRF
Defining automatic route filtering
Assigning a VRF Routing Instance to an Interface
Setting up cooperative route filtering
Importing and exporting route maps
Defining an extended community for use with a route map
Creating a VPNv4 route reflector
Configuring autonomous system number override
Configuring a PE to allow routes with its AS number
Setting up LSPs per VRF
Configuring OSPF sham links
Configuring OSPF on a PE device to redistribute BGP-VPNv4 or VPNv6 routes
Ping and Traceroute for layer-3 VPNs
Displaying BGP or MPLS VPNv4 or VPNv6 information
Displaying VPNv4/VPNv6 route information
Displaying VPNv4/VPNv6 route information for a specified IP address
Displaying VPNv4/VPNv6 attribute entries information
Displaying VPNv4/VPNv6 neighbor information
Displaying received ORFs information for a specified VPNv4/VPNv6 neighbor
Displaying a specified neighbor VPNv4/VPNv6 routes
Displaying routes summary for a specified VPNv4/VPNv6 neighbor
Displaying summary route information
Displaying the VPNv4/VPNv6 route table
Displaying the best VPNv4/VPNv6 routes
Displaying best VPNv4/VPNv6 routes that are not in the IP route table
Displaying VPNv4/VPNv6 routes with unreachable destinations
Displaying information for a specific VPNv4/VPNv6 route
Displaying VPNv4/VPNv6 route details
Displaying additional BGP or MPLS VPN information
Displaying VRF information
Displaying the IP route table for a specified VRF
Displaying ARP VRF information
Displaying OSPF information for a VRF
Displaying OSPF area information for a VRF
Displaying OSPF ABR and ASBR information for a VRF
Displaying general OSPF configuration information for a VRF
Displaying OSPF external link state information for a VRF
Displaying OSPF link state information for a VRF
Displaying OSPF Interface Information
Displaying OSPF neighbor information for a VRF
Displaying the routes that have been redistributed into OSPF
Displaying OSPF route information for a VRF
Displaying OSPF sham links
Displaying OSPF trap status for a VRF
Displaying OSPF virtual links for a VRF
Displaying OSPF virtual neighbor information for a VRF
Displaying IP extcommunity list information
Displaying the IP static route table for a VRF
Displaying the static ARP table for a VRF
Displaying TCP connections for a VRF
Displaying IP route information for a VRF
BGP or MPLS VPN sample configurations
Basic configuration example for IBGP on the PEs
Assigning an AS number to a PE
Assigning a loopback interface
Configuring an IBGP neighbor on a PE
Configuring EBGP on a CE router
Configuring EBGP on a PE router
EBGP for Route Exchange
Static Routes for Route Exchange
Configuring a static default route on a CE router
Configuring a static default route on a PE router
OSPF for Route Exchange
Configuring OSPF on the CE router
Enabling OSPF on the CE router interface
Configuring the VRF on the PE router to redistribute OSPF routes
Configuring OSPF on the PE router to redistribute BGP-VPNv4 routes
Enabling OSPF on the PE Router Interface
OSPF to CE Configuration Example
Cooperative Route Filtering
Using an IP Extcommunity Variable with Route Map
Autonomous System Number Override
Setting an LSP for Each VRF on a PE
OSPF Sham Links
PE 1 configuration
PE 2 configuration
Label Distribution Protocol
Section contents:
LDP overview
When used to create LSP tunnels, LDP allows a set of destination IP prefixes (known as a Forwarding Equivalence Class or FEC) to be associated with an LSP.
Configuring LDP on an Interface
For an LDP session between routers, you must configure LDP on an interface to allow the device to advertise its loopback interface to the peers.
Configuring the LDP session keepalive interval
You can configure the LDP session keepalive interval and the keepalive timeout value is derived as the product of the keepalive interval times the keepalive interval count.
Configuring the LDP session keepalive timeout
After an LDP session is established, an LSR maintains the integrity of the session by sending keepalive messages. The keepalive timer for each peer session resets whenever it receives any LDP protocol message or a keepalive message on that session. When the keepalive timer expires, LDP concludes that the TCP connection is bad or the peer is dead and terminates the session.
LDP Hello interval and Hello Hold timeout timers
The LDP Hello interval and Hello Hold Timeout timers are used to establish Hello Adjacency between peers. The Hello interval is the time period between which the LSR sends out Hello messages and the Hello Hold timeout is the amount of time that the sending LSR maintains its record of Hellos from the receiving LSR without receipt of another Hello message.
Resetting LDP neighbors
You can terminate and re-establish an MPLS LDP neighbor session when at least one LDP Hello adjacency exists with the peer. When the LDP session terminates, the database associated with the LDP session is also cleared.
LDP route injection
By default, LDP advertises all /32 prefixes that are learned from all the loopback interfaces to all other LDP peers. LDP route injection enables LDP to advertise other prefixes that are learned by IGP. When you enable route injection, it references prefix lists for permitted and denied prefixes. When IGP learns these prefixes, the device injects them into LDP and advertises the corresponding labels to the LDP peers.
LDP inbound-FEC filtering
MPLS LDP inbound-FEC filtering filters inbound label bindings on a MPLS router. You can control the amount of memory and CPU processing involved in installing and advertising label bindings not used for forwarding.
LDP outbound FEC filtering
LDP outbound FEC filtering allows LDP to perform outbound filtering for label advertisement. It gives you the ability to control which FECs can be advertised and to which LDP neighbors. It also reduces the number of labels distributed to neighbors and the number of messages exchanged with peers. Through this feature, LDP scalability and convergence, security, and performance are improved.
Label withdrawal delay timer
The label withdrawal delay timer allows you to configure a delay when sending a label withdraw message for a FEC to a neighbor.
LDP ECMP for transit LSR
LDP Equal-Cost Multi-Path (ECMP) for transit LSR provides ECMP support for transit routers on an LDP LSP.
MPLS LDP-IGP Synchronization
MPLS LDP-IGP synchronization provides a means to synchronize LDP and IGPs to minimize MPLS packet loss.
LDP Graceful Restart
LDP Graceful Restart (GR) helps minimize MPLS traffic loss when an LDP component is restarting in a router that is capable of preserving its MPLS forwarding states across restart. LDP GR is based on RFC 3478 (Graceful Restart mechanism for Label Distribution Protocol).
Configurable LDP router ID
LDP uses LDP messages to communicate between LDP peers for the correct functioning of LDP. All LDP messages contains a LDP header which is composed of LDP version, length of message, LDP ID, and is followed by a message. The LDP ID for LDP is composed of the LSR-ID and label space. The LSR ID is the first available loopback interface address. However, you can specify an IP address of your choice to use as the LSR ID for the LDP identifier.
Displaying LDP information and statistics
The
show mpls ldp
command and options allows you to display LDP information and statistics.
Configuration Example of LDP-Enabled LSRs
