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EVPN-VXLAN with an IPv6 Underlay

SUMMARY This topic describes how to set up an IPv6 underlay for the VXLAN overlay tunneling in an EVPN-VXLAN fabric.

IPv6 Underlay Support in EVPN-VXLAN Fabrics

Ethernet VPNs (EVPNs) connect devices with Layer 2 virtual bridges. Virtual Extensible LANs (VXLANs) establish overlay tunnels that stretch the Layer 2 connections over a Layer 3 network. In EVPN-VXLAN network configurations, a leaf or spine device can function as a VXLAN gateway at Layer 2, Layer 3, or both layers. The underlay network for the VXLAN overlay can be an IPv4 or an IPv6 network. This topic describes using an IPv6 underlay instead of an IPv4 underlay.

Benefits of Using an IPv6 Underlay with a VXLAN Overlay

  • With an IPv6 underlay VXLAN tunnel configuration, you can take advantage of the expanded addressing capabilities and efficient packet processing that the IPv6 protocol offers.


In EVPN-VXLAN installations, you configure a VXLAN overlay on Layer 2 or Layer 3 VXLAN gateway devices called virtual tunnel endpoints (VTEPs). The VXLAN overlay extends virtual tunnels between VTEPs over the underlying IP fabric. On supporting platforms, you can configure the IP underlay with IPv6 addressing to support the VXLAN overlay tunnels. For example:

Figure 1: EVPN-VXLAN Fabric with an IPv6 Underlay EVPN-VXLAN Fabric with an IPv6 Underlay

When you use an IPv6 underlay, the VTEPs encapsulate VXLAN packets with an IPv6 outer header and tunnel the packets through an IPv6 underlay network.

Figure 2: IPv6 Underlay VXLAN Packet Encapsulation IPv6 Underlay VXLAN Packet Encapsulation

You can configure an IPv6 underlay for the VXLAN overlays in an EVPN-VXLAN fabric starting in:

  • Junos OS Release 17.3R1 on MX Series routers.

  • Junos OS Release 21.2R2 and 21.4R1 on QFX Series switches (QFX5120 switches and the QFX10000 line of switches).

IPv6 underlay configurations are similar to IPv4 underlay configurations, except you set the VTEP source addresses as IPv6 addresses. You also assign IPv6 addresses in the underlay and establish reachability using the IPv6 protocol.

Underlay Routing Protocols with an IPv6 Underlay

We've qualified an IPv6 underlay with the following routing protocols in the underlay configuration:

  • BGP—Internal BGP (iBGP) and external BGP (eBGP)

  • OSPFv3—Open Shortest Path First (OSPF) routing protocol for IPv6

EVPN-VXLAN Features Supported with an IPv6 Underlay

We support the following EVPN-VXLAN features with an IPv6 underlay:

Limitations in IPv6 Underlay Support

Note the following limitations in IPv6 underlay support:

  • You can't mix IPv4 and IPv6 underlay configurations for the VXLAN overlays across the EVPN instances in the same fabric.

  • We don't support the Open vSwitch database (OVSDB) management protocol for IPv6 underlays.

  • (MX Series routers and EX9200 switches) We don't support EVPN Type 5 routes with an IPv6 underlay.

  • (QFX10002-60C switches) You can only use enterprise style interface configuration; we don't support service provider style interface configuration and Q-in-Q tunneling with IPv4 or IPv6 underlays on these switches.

  • (QFX Series switches) You must use MAC-VRF routing instances with EVPN protocol and VXLAN encapsulation. We don't support IPv6 underlays with other instance types such as evpn, evpn-vpws, virtual-switch or the default switching instance.

  • We don't support IPv6 underlays with:

    • EVPN multicast and multicast optimization features.

    • DCI for EVPN-VXLAN in the data center to EVPN-VXLAN in a WAN using the gateway interconnection model.

Configure an IPv6 Underlay with EVPN-VXLAN

This section describes the key steps to configure the IP underlay for the VXLAN tunnels in an EVPN-VXLAN fabric to use the IPv6 protocol (instead of an IPv4 underlay). You can use an IPv6 underlay in many different EVPN-VXLAN configurations and use cases. See Example: Configure an IPv6 Underlay for Layer 2 VXLAN Gateway Leaf Devices for a simple example that uses OSPFv3 in the underlay and iBGP for the overlay connectivity.

Keep the following configuration options and requirements in mind:

  • You can configure your EVPN-VXLAN fabric with any of the underlay routing protocols that support IPv6 underlays. See Underlay Routing Protocols with an IPv6 Underlay.

  • QFX Series switches support IPv6 underlays only with MAC-VRF routing instances in EVPN-VXLAN fabrics. You must configure your EVPN instances with VXLAN encapsulation in all MAC-VRF routing instances. The routing instances mentioned in the steps here are always EVPN-VXLAN MAC-VRF instances. See MAC-VRF Routing Instance Type Overview for more about MAC-VRF instances.

To enable an IPv6 underlay for VXLAN tunneling, include these items in your EVPN-VXLAN fabric configuration:

  1. Assign IPv4 and IPv6 addresses to the loopback interface on the devices that serve as Layer 2 or Layer 3 VXLAN gateway VTEPs.
  2. Configure the underlay and EVPN instance device connectivity for the overlay using any of the supported routing protocols with IPv6 addressing. (See Underlay Routing Protocols with an IPv6 Underlay.)
  3. In the EVPN routing instance, configure the underlay VTEP source interface as the device's loopback IPv6 address. On a QFX Series switch, for example:
  4. The underlay uses the IPv6 address family. However, for BGP handshaking to work in the overlay, you must configure the router ID as the loopback IPv4 address:
  5. (QFX Series Broadcom-based switches in Junos OS Release 21.2R2 only) Enable the Broadcom VXLAN flexible flow feature. You don’t need this step in later releases, which have this option enabled in the default configuration on any affected Junos devices. After you set this option, you must reboot the device for the change to take effect.