VXLAN Configuration Module

This configuration module configures the VXLAN data plane, VLAN-to-VXLAN mapping, and static head-end replication.

The module supports the following features:

VLAN-to-VXLAN bridging implementing VLAN-based Service Interface as defined in RFC 7432/RFC 8365.
Single VXLAN interface per device
The default loopback interface is used as the VTEP IP address; you can also specify an alternate loopback interface as the VTEP source interface
Static per-VLAN or per-node ingress replication
Mapping a subset of VLANs into VXLAN VNIs

The module requires the VLAN module (to set up the vlans dictionary) and should be used with a routing protocol module to establish VTEP-to-VTEP connectivity.

Platform Support

The following table describes the per-platform support of individual VXLAN features:

Operating system	VXLAN bridging	Per-VLAN replication	IPv6 VTEP
Arista EOS	✅	✅	❌
Aruba AOS-CX	✅	✅	❌
Cisco CSR 1000v	✅	✅	❌
Cisco Nexus OS	✅	✅	❌
Cumulus Linux 4.x	✅	✅	❌
Cumulus 5.x (NVUE)	✅	✅	❌
Dell OS10	✅	✅	❌
FRR	✅	✅	✅
Nokia SR Linux	✅ ❗	❌	❌
Nokia SR OS	✅	❌	❌
vJunos-switch	✅	✅	❌
VyOS	✅	✅	✅

Tip

See VXLAN Integration Tests Results for more details.

Global and Node Parameters

vxlan.domain (node or global) – Ingress replication domain. Optional, default: global. Use this parameter to build several isolated bridging domains within your lab.
vxlan.flooding (node or global) – A mechanism used to implement VXLAN flooding. Optional, default: static.
vxlan.vlans (node or global) – the list of VLANs to be mapped into VXLAN VNIs. When missing, defaults to all VLANs.
vxlan.use_v6_vtep (global) – Use the IPv6 Loopback address as VTEP address. Use this parameter to enable VXLAN-over-IPv6 with ingress replication. All VXLAN-enabled lab devices must support VXLAN-over-IPv6 transport.

The only supported value for vxlan.flooding parameter for non-EVPN deployments is static (statically configured ingress replication). The EVPN module changes the default vxlan.flooding value to evpn.

Module Parameters

The following default parameters influence VNI assignment:

vxlan.start_vni: Specifies the first auto-assigned VNI (default: 100000).

To change the module defaults, set defaults.vxlan.value parameter(s) in lab topology.

Default Behavior

All VLANs are mapped into VXLAN VNIs and bridged between VXLAN-enabled nodes.
Without specifying vxlan.domain for individual nodes or groups of nodes, all VXLAN-enabled nodes belong to a single global bridging domain.
VXLAN flooding is implemented with ingress replication. The VXLAN module builds per-VLAN VTEP replication lists for each node. Whether the device configuration uses VLAN-level or global replication lists is an implementation decision.

Selecting VXLAN-enabled VLANs

Global VLANs that should be extended with VXLAN transport are specified in the vxlan.vlans global- or node-level list. When that parameter is missing, all VLANs use VXLAN transport.

VLANs specified in the vxlan.vlans list must be valid VLAN names, but do not have to be present on every node.

You can also enable a VLAN for VXLAN transport by setting the vni VLAN parameter to an integer value.

Auto-Assign VNI

All VLANs specified in the vxlan.vlans list will get a vni attribute. To turn off the auto-assignment for individual VLANs, set the vni VLAN parameter to an integer value (static VNI) or False (no VNI).

For every VLAN, the VXLAN configuration module tries to use vxlan.start_vni + vlan.id as the VLAN VNI and reverts to sequentially allocated values when that VNI is already in use.

Building Ingress Replication Lists

The VXLAN module builds ingress replication lists for all nodes with vxlan.flooding set to static. Each VLAN-specific ingress replication list includes the VTEP IP addresses of all other nodes in the same vxlan.domain that have a VLAN with the same vni attribute.

All VLAN-specific ingress replication lists are merged into a node-level ingress replication list. Some devices support per-VLAN replication lists while others might use node-level replication lists; the only difference is the amount of irrelevant traffic replicated across the VXLAN transport network.

Changing the VXLAN VTEP Source interface/address

netlab assumes you want to use the first loopback interface/address as the VTEP source interface/address.

If you want your node to use a different loopback interface as VXLAN VTEP, you need to define a loopback link, and add the vxlan.vtep attribute set to true, i.e.:

links:
- sw1:
  type: loopback
  pool: vteps
  vxlan.vtep: true

However, if you specify multiple loopback links with the vxlan.vtep attribute, only the first one will be considered.

Interactions with the Routing Protocols

netlab treats VXLAN-based VLANs like any other VLAN and enables routing protocols on them. However, when the cost of the overlay (VLAN) interface is lower than the cost of the underlay path, routing black holes could occur (more details).

You can solve this problem in numerous ways:

Use layer-2-only VLANs (set vlan.mode to bridge)
Put VXLAN-enabled VLANs in a VRF
Disable underlay routing protocols on VXLAN-based VLANs with a VLAN setting similar to vlans.tenant.ospf: False

Example

We want to create a simple two-switch network transporting two VLANs across a VXLAN backbone. We have to define the VLANs first:

vlans:
  red:
    mode: bridge
  blue:
    mode: bridge

Next, we’ll define the switches and hosts groups to simplify node configuration. All switches will run Arista EOS and use VLAN, VXLAN, and OSPF modules.

groups:
  hosts:
    members: [ h1, h2, h3, h4 ]
    device: linux
  switches:
    members: [ s1,s2 ]
    device: eos
    module: [ vlan,vxlan,ospf ]

We also have to define individual nodes. Please note that we set node parameters (modules and device type) within switches and hosts groups.

nodes: [ h1, h2, h3, h4, s1, s2 ]

Finally, we have to define the links in our lab:

links:
- h1:
  s1:
    vlan.access: red
- h2:
  s2:
    vlan.access: red
- h3:
  s1:
    vlan.access: blue
- h4:
  s2:
    vlan.access: blue
- s1:
  s2:

Please note we did not have to define:

VLAN tags or VXLAN VNIs
VLAN-to-VXLAN mappings
Any other VLAN or VXLAN parameters apart from VLAN names
IP addresses or routing protocol parameters