EVPN Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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EVPN Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Flow label support for EVPN

Updated: June 10, 2026

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Explains how flow label support for EVPN enables provider routers to optimize traffic distribution using flow-based load balancing in an MPLS environment.

A flow label support for EVPN is a feature that

  • enables provider (P) routers to use flow-based load balancing to forward traffic between PE devices

  • utilizes Flow-Aware Transport (FAT) of pseudowires (PW) over an MPLS packet-switched network for load balancing traffic across BGP-based signaled pseudowires for EVPN and

  • improves traffic distribution across equal cost multipaths (ECMP) or link-bundled paths in the core.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Flow label support for EVPN

 Release 26.2.1

Introduced in this release on: Modular Systems (8800 [LC ASIC: K100])(select variants only*);

*This feature is supported on Cisco 88-LC1-48Y8H-EM line cards.

Flow label support for EVPN

 Release 25.4.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*)

*This feature is now supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A

  • 8011-12G12X4Y-D

Flow label support for EVPN

Release 25.1.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100]) (select variants only*)

*This feature is now supported on the Cisco 8011-4G24Y4H-I routers.

Flow label support for EVPN

Release 24.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100, K100])(select variants only*); Modular Systems (8800 [LC ASIC: Q100, P100])(select variants only*)

The Flow Label Support for EVPN functionality is now extended to:

  • 8212-48FH-M

  • 8712-MOD-M

  • 8711-32FH-M

  • 88-LC1-52Y8H-EM

  • 88-LC1-12TH24FH-E

  • 88-LC1-36EH

Flow label support for EVPN

Release 7.3.2

The Flow Label support improves traffic distribution by enabling flow-based load balancing between provider edge devices. It uses Flow-Aware Transport (FAT) pseudowires over an MPLS network to efficiently manage traffic across BGP-signaled pseudowires in an Ethernet VPN. Flow labels, based on packet flows, help optimize traffic across equal cost multipaths or link-bundled paths.

Optimize traffic distribution using flow label

A service provider deploying EVPN can use this feature to optimize traffic distribution across multiple paths in their MPLS core network. A network with high traffic volumes can benefit from reduced congestion and improved performance by leveraging flow-based load balancing.

Flow-based load balancing with FAT pseudowires

FAT pseudowires (PWs) in EVPN provides the capability to identify individual flows within a PW, allowing routers to load-balance traffic effectively. When ECMP is used, FAT PWs ensure better traffic distribution by creating a flow label based on indivisible packet flows entering an imposition PE. This flow label is inserted as the lowermost label in the packet. P routers then use the flow label for load balancing.

A flow is identified by either:

  • The source and destination IP address of the traffic, or

  • The source and destination MAC address of the traffic.

Supported EVPN services

Flow label support for EVPN is supported on EVPN E-Line and EVPN E-LAN services in both single-homing and multihoming deployments. You enable the flow-label command at the EVPN instance (EVI) level. After it is enabled for an EVI, the flow-label configuration applies to all services attached to that EVI.

FAT PWs are designed to improve traffic distribution across ECMPs and link bundles by introducing greater entropy through flow labels. This ensures efficient utilization of network resources and enhances performance.

Summary

The process of distributing flows over Equal-Cost Multi-Paths (ECMPs) and bundle links in a FAT Pseudowire (PW) involves the use of flow labels to enhance traffic load balancing.

The key components involved in the process are:

  • Flow label: A unique identifier derived from source and destination MAC and IP addresses, inserted into the label stack.

  • Ingress PE (PE1):Adds the flow label to the traffic.

  • Egress PE (PE2): Discards the flow label and uses a single EVPN label for unicast traffic.

  • Core routers (P routers): Use the flow label for load balancing.

Workflow

These stages describe how flow-based load balancing operates to optimize traffic distribution across PE device.

  1. Flow label generation:

    • The ingress PE (PE1) generates a flow label for each unique incoming flow based on source and destination MAC and IP addresses.

    • The flow label is inserted after the VC label and before the control word (if any).

  2. Traffic forwarding:

    • PE1 forwards the traffic with the flow label to the core routers.

    • Core routers use the flow label, along with other information like MAC and IP addresses, to perform load balancing across ECMPs and bundle links.

  3. Traffic handling at egress PE:

    • The egress PE (PE2) receives the traffic and discards the flow label.

    • PE2 uses a single EVPN label for all unicast traffic, ensuring compatibility with mixed traffic types (with or without flow labels).

    The process enables efficient load balancing of traffic across ECMPs and bundle links, improving network performance and resource.

Configure flow label for EVPN

Configure a flow label for EVPN on both PE1 and PE2 to enable load balancing and efficient traffic management.

EVPN services, such as E-Line and E-LAN, use MPLS encapsulation. Configuring a flow label ensures proper load balancing across the network.

Before you begin

  • Ensure that PE1 and PE2 are running compatible software versions.

  • Verify that the interfaces and EVPN instances are pre-configured.

Procedure

1.

Configure L2VPN xconnect group.

Example:


Router# configure 
Router(config)# l2vpn 
Router(config-l2vpn)# xconnect group evpn-vpws
Router(config-l2vpn-xc)# p2p evpn1
Router(config-l2vpn-xc-p2p)# interface TenGigE0/0/0/0
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 1 target 2 source 1
Router(config-l2vpn-xc-p2p)# commit
2.

Configure the EVPN instance.

Example:


Router# configure 
Router(config)# evpn
Router(config-evpn)# evi 1
Router(config-evpn-instance)# load-balancing
Router(config-evpn-instance-lb)# flow-label static
Router(config-evpn-instance-lb)# commit
3.

Flow label for EVPN running configuration.

Example:


l2vpn
 xconnect group evpn-vpws
  p2p evpn1
   interface TenGigE0/0/0/0
   neighbor evpn evi 1 target 2 source 1
   !
  !
evpn
 evi 1
   load-balancing
   flow-label static
  !
!
4.

Use the show l2vpn xconnect detail command to verify that EVPN flow label is configured.

Example:


Router# show l2vpn xconnect detail
Group evpn-vpws, XC evpn1, state is up; Interworking none
  AC: TenGigE0/0/0/0, state is up
    Type Ethernet
    MTU 1500; XC ID 0x1; interworking none
    Statistics:
      packets: received 21757444, sent 0
      bytes: received 18226521128, sent 0
  EVPN: neighbor 100.100.100.2, PW ID: evi 1, ac-id 2, state is up ( established )
    XC ID 0xc0000001
    Encapsulation MPLS
   Encap type Ethernet, control word disabled
    Sequencing not set
    LSP : Up
    Flow Label flags configured (Tx=1,Rx=1) statically
 
      EVPN         Local                          Remote                       
      ------------ ------------------------------ -----------------------------
      Label        64002                          64002                        
      MTU          1500                           1500                         
      Control word disabled                       disabled                     
      AC ID        1                              2                            
      EVPN type    Ethernet                       Ethernet                     
          
      ------------ ------------------------------ -----------------------------
    Create time: 30/10/2018 03:04:16 (00:00:40 ago)
    Last time status changed: 30/10/2018 03:04:16 (00:00:40 ago)
    Statistics:
      packets: received 0, sent 21757444
      bytes: received 0, sent 18226521128