Segment Routing v6 Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Segment Routing v6 Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

IPv4 L3VPN active-standby redundancy using port-active mode

Updated: September 8, 2026

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Explains how port-active mode provides active-standby redundancy for multihomed IPv4 L3VPN services and describes DF election, load balancing, failover, restrictions, and configuration.

An IPv4 L3VPN active-standby redundancy using port-active mode is a Segment Routing IPv6 (SRv6) service that

  • provides all-active per-port load balancing for multihoming

  • determines traffic forwarding based on specific interfaces rather than per-flow across multiple Provider Edge (PE) routers, and

  • enables faster convergence by using designated forwarder (DF) election through modulo calculation, where byte 10 of the Ethernet Segment Identifier (ESI) is used to detect the active PE router and bring down the standby PE router’s interface

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

IPv4 L3VPN active-standby redundancy using port-active mode

 Release 25.4.1

Introduced in this release on: Fixed Systems (8700 [ASIC: K100])(select variants only*)

This feature enables active-standby redundancy using port-active mode for IPv4 L3VPN services over SRv6, providing high availability and efficient load balancing in multihomed networks.

Traffic forwarding is based on specific interfaces, not per flow, across multiple Provider Edge (PE) routers. Rapid failover is achieved through designated forwarder (DF) election using modulo calculation on byte 10 of the Ethernet Segment Identifier (ESI).

This enhances network resilience and operational efficiency by ensuring faster convergence and minimal service disruption.

This feature is now supported on:

  • 8711-48Z-M

Enhanced multihoming efficiency with active-standby redundancy using port-active mode

This feature ensures high availability and efficient traffic management in multihomed IPv4 L3VPN networks. By leveraging per-port active-standby redundancy, it provides robust load balancing and rapid failover, minimizing service disruption. The port-active mode simplifies traffic forwarding decisions based on specific interfaces and accelerates convergence using DF election, enhancing overall network resilience and operational efficiency.

Benefits of active-standby redundancy using port-active mode

  • Load balancing performed per interface (port), simplifying forwarding decisions.

  • DF election based on modulo calculation of the ESI to identify the active PE.

  • Standby PE interfaces disabled to avoid forwarding loops and conflicts.

  • Rapid failover and convergence by re-electing the DF upon link or port failure.

  • Enhanced network efficiency, reliability, and resilience in multihomed IPv4 L3VPN deployments.

Restrictions of active-standby redundancy using port-active mode

  • This feature can only be configured on bundle interfaces.

How SRv6 services for L3VPN active-standby redundancy using port-active mode work

Summary

The SRv6 Services for L3VPN Active-Standby Redundancy using Port-Active Mode process ensures high availability and efficient traffic management. PE routers exchange EVPN ES routes via BGP, then individually determine an ordered list of PEs. A modulo calculation designates one PE as the active forwarder (DF), while others disable their bundles. In the event of a failure, the active DF withdraws its route, prompting a re-election and quick resumption of forwarding duties by a newly elected DF.

Workflow

These stages describe how SRv6 services for IPv4 L3VPN active-standby redundancy using port-active mode works:

  1. PE routers exchange EVPN ES routes. All PE routers connected to the multihomed ES exchange EVPN ES routes across BGP.

  2. Each PE router creates an ordered list and assigns an ordinal.

    • Each PE router creates an ordered list of all PE IP addresses connected to the ES.

    • Each PE router assigns itself an ordinal based on its position in this list.

  3. A modulo calculation determines the Designated Forwarder (DF).

    • Using the ordinals, a modulo calculation determines which PE becomes the Designated Forwarder (DF) for the ES.

    • For the modulo calculation, byte 10 of the Ethernet Segment Identifier (ESI) is used.

  4. The elected DF forwards traffic and non-DF PEs disable bundles.

    • The PE elected as DF actively forwards traffic for the ES.

    • All other PEs (non-DF) disable their respective bundles for that ES.

  5. The active DF PE withdraws its ES route upon failure.

    Upon a link or port failure, the active DF PE withdraws its ES route.

  6. A new DF election is triggered, and a new PE resumes forwarding.

    • This withdrawal triggers a new DF election among all PEs servicing the ES.

    • A new PE is elected as DF and resumes forwarding duties.

Configure SRv6 services L3VPN active-standby redundancy using port-active mode

Configure SRv6 services to provide L3VPN active-standby redundancy using port-active mode under an Ethernet Segment (ES).

Procedure

  1. Configure Ethernet link bundle interface.

    Example:

    Router# configure
Router(config)# interface Bundle-Ether10
Router(config-if)# ipv4 address 10.0.0.2 255.255.255.0
Router(config-if)# ipv6 address 2001:DB8::1
Router(config-if)# lacp period short
Router(config-if)# mac-address 1.2.3
Router(config-if)# bundle wait-while 0
Router(config-if)# exit
Router(config)# interface GigabitEthernet 0/2/0/5
Router(config-if)# bundle id 14 mode active
Router(config-if)# commit

  2. Configure the physical interface to join the bundle.

    Example:

    Router# configure
Router(config)# evpn
Router(config-evpn)# interface Bundle-Ether10
Router(config-evpn-ac)# ethernet-segment
Router(config-evpn-ac-es)# identifier type 0 11.11.11.11.11.11.11.11.14
Router(config-evpn-ac-es)# load-balancing-mode port-active
Router(config-evpn-ac-es)# commit

  3. Configure the BGP address family session for EVPN.

    Example:

    
Router# configure
Router(config)# router bgp 100
Router(config-bgp)# bgp router-id 192.168.0.2
Router(config-bgp)# address-family l2vpn evpn
Router(config-bgp)# neighbor 192.168.0.3
Router(config-bgp-nbr)# remote-as 200
Router(config-bgp-nbr)# update-source Loopback 0
Router(config-bgp-nbr)# address-family l2vpn evpn
Router(config-bgp-nbr)# commit

  4. Running configuration active-standby redundancy using port-active mode.

    Example:

    
interface Bundle-Ether14
 ipv4 address 14.0.0.2 255.255.255.0
 ipv6 address 14::2/64
 lacp period short
 mac-address 1.2.3
 bundle wait-while 0
!
interface GigabitEthernet0/2/0/5
 bundle id 14 mode active
!
evpn
 interface Bundle-Ether14
  ethernet-segment
   identifier type 0 11.11.11.11.11.11.11.11.14
   load-balancing-mode port-active
  !
 !
!
router bgp 100
 bgp router-id 192.168.0.2
 address-family l2vpn evpn
 !
 neighbor 192.168.0.3
  remote-as 100
  update-source Loopback0
  address-family l2vpn evpn
  !
 !
!

  5. Verify the SRv6 services L3VPN active-standby redundancy using port-active mode configuration.

    1. Verify ethernet-segment details on active DF router.

      Example:

      
Router# show evpn ethernet-segment interface Bundle-Ether14 detail 
Ethernet Segment Id      Interface                          Nexthops            
------------------------ ---------------------------------- --------------------
0011.1111.1111.1111.1114 BE14                               192.168.0.2
                                                            192.168.0.3
    ES to BGP Gates   : Ready
  ES to L2FIB Gates : Ready
  Main port         :
     Interface name : Bundle-Ether14
     Interface MAC  : 0001.0002.0003
     IfHandle       : 0x000041d0
     State          : Up
     Redundancy     : Not Defined
  ESI type          : 0
     Value          : 11.1111.1111.1111.1114
  ES Import RT      : 1111.1111.1111 (from ESI)
  Source MAC        : 0000.0000.0000 (N/A)
  Topology          :
     Operational    : MH
     Configured     : Port-Active
  Service Carving   : Auto-selection
     Multicast      : Disabled
  Peering Details   :
     192.168.0.2 [MOD:P:00]
     192.168.0.3 [MOD:P:00]

  Service Carving Results:
     Forwarders     : 0
     Permanent      : 0
     Elected        : 0
     Not Elected    : 0
  MAC Flushing mode : STP-TCN
  Peering timer     : 3 sec [not running]
  Recovery timer    : 30 sec [not running]
  Carving timer     : 0 sec [not running]
  Local SHG label   : None
  Remote SHG labels : 0
    2. Verify bundle Ethernet configuration on active DF router.

      Example:

      
Router# show bundle bundle-ether 14 
Bundle-Ether14
  Status:                                    Up
  Local links <active/standby/configured>:   1 / 0 / 1
  Local bandwidth <effective/available>:     1000000 (1000000) kbps
  MAC address (source):                      0001.0002.0003 (Configured)
  Inter-chassis link:                        No
  Minimum active links / bandwidth:          1 / 1 kbps
  Maximum active links:                      64
  Wait while timer:                          Off
  Load balancing:                            
    Link order signaling:                    Not configured
    Hash type:                               Default
    Locality threshold:                      None
  LACP:                                      Operational
    Flap suppression timer:                  Off
    Cisco extensions:                        Disabled
    Non-revertive:                           Disabled
  mLACP:                                     Not configured
  IPv4 BFD:                                  Not configured
  IPv6 BFD:                                  Not configured

  Port                  Device           State        Port ID         B/W, kbps
  --------------------  ---------------  -----------  --------------  ----------
  Gi0/2/0/5             Local            Active       0x8000, 0x0003     1000000
      Link is Active
    3. Verify ethernet-segment details on standby DF router.

      Example:

      Router# show evpn ethernet-segment interface bundle-ether 10 detail

Router# show evpn ethernet-segment interface Bundle-Ether24 detail
Ethernet Segment Id      Interface                          Nexthops            
------------------------ ---------------------------------- --------------------
0011.1111.1111.1111.1114 BE24                               192.168.0.2
                                                            192.168.0.3
  ES to BGP Gates   : Ready
  ES to L2FIB Gates : Ready
  Main port         :
     Interface name : Bundle-Ether24
     Interface MAC  : 0001.0002.0003
     IfHandle       : 0x000041b0
     State          : Standby
     Redundancy     : Not Defined
  ESI type          : 0
     Value          : 11.1111.1111.1111.1114
  ES Import RT      : 1111.1111.1111 (from ESI)
  Source MAC        : 0000.0000.0000 (N/A)
  Topology          :
     Operational    : MH
     Configured     : Port-Active
  Service Carving   : Auto-selection
     Multicast      : Disabled
  Peering Details   :
     192.168.0.2 [MOD:P:00]
     192.168.0.3 [MOD:P:00]

  Service Carving Results:
     Forwarders     : 0
     Permanent      : 0
     Elected        : 0
     Not Elected    : 0
  MAC Flushing mode : STP-TCN
  Peering timer     : 3 sec [not running]
  Recovery timer    : 30 sec [not running]
  Carving timer     : 0 sec [not running]
  Local SHG label   : None
  Remote SHG labels : 0
    4. Verify bundle configuration on standby DF router.

      Example:

      Router# show bundle bundle-ether 24 
 
Bundle-Ether24
  Status:                                    LACP OOS (out of service)
  Local links <active/standby/configured>:   0 / 1 / 1
  Local bandwidth <effective/available>:     0 (0) kbps
  MAC address (source):                      0001.0002.0003 (Configured)
  Inter-chassis link:                        No
  Minimum active links / bandwidth:          1 / 1 kbps
  Maximum active links:                      64
  Wait while timer:                          Off
  Load balancing:                            
    Link order signaling:                    Not configured
    Hash type:                               Default
    Locality threshold:                      None
  LACP:                                      Operational
    Flap suppression timer:                  Off
    Cisco extensions:                        Disabled
    Non-revertive:                           Disabled
  mLACP:                                     Not configured
  IPv4 BFD:                                  Not configured
  IPv6 BFD:                                  Not configured

  Port                  Device           State        Port ID         B/W, kbps
  --------------------  ---------------  -----------  --------------  ----------
  Gi0/0/0/4             Local            Standby      0x8000, 0x0002     1000000
      Link is in standby due to bundle out of service state