In which configuration mode is feature nv overlay used?

The feature nv overlay command is entered in Global Config mode on Cisco NX-OS devices.

vxlanGlobal Config

feature nv overlay

Enables the NX-OS overlay feature, which is required for VXLAN and other overlay networking technologies.

Definition: feature nv overlay is a Cisco NX-OS global config command. Enables the NX-OS overlay feature, which is required for VXLAN and other overlay networking technologies.

Overview

The 'feature nv overlay' command is a foundational command on Cisco Nexus switches running NX-OS that enables the Network Virtualization (NV) Overlay feature set. This feature is essential for deploying overlay networks such as VXLAN (Virtual Extensible LAN) and related technologies like EVPN (Ethernet VPN). Without this feature enabled, the switch will not allow configuration of VXLAN tunnel endpoints (VTEPs), Network Virtualization Edge (NVE) interfaces, or VXLAN Network Identifiers (VNIs).

VXLAN is a network virtualization technology that extends Layer 2 segments over a Layer 3 underlay network, enabling scalability and flexibility in data center fabrics. The NV overlay feature provides the control plane and data plane components necessary for VXLAN operation. On Nexus switches, this command is typically one of the first steps in configuring a VXLAN EVPN fabric, alongside enabling features like 'feature ospf' or 'feature bgp' for the underlay routing.

When to use this command: It should be executed in global configuration mode before any VXLAN-specific configuration. It is required on both spine and leaf switches in a VXLAN fabric, though spines may not need NVE interfaces. Platform-specific behavior: On Nexus 9000 series switches, the command is supported from NX-OS version 6.1(2)I2(1) onwards. On older platforms like Nexus 7000, VXLAN support may require specific line cards and NX-OS versions. In troubleshooting workflows, if VXLAN configurations are rejected, verifying that 'feature nv overlay' is enabled is the first step.

Syntax·Global Config

feature nv overlay

When to Use This Command

Enabling VXLAN on a Nexus switch to support network virtualization and overlay networks.
Preparing a spine or leaf switch for VXLAN EVPN fabric deployment.
Activating overlay features before configuring VXLAN tunnel endpoints (VTEPs) and VNIs.
Enabling the NVE (Network Virtualization Edge) interface for VXLAN termination.

Parameters

Parameter	Syntax	Required	Description
No parameters	feature nv overlay	Required	This command has no additional parameters. It simply enables the NV overlay feature globally on the switch.

Command Examples

Enable NV Overlay Feature

configure terminal
feature nv overlay

switch(config)# feature nv overlay
switch(config)#

The command enables the NV overlay feature globally. No output indicates success; the prompt returns without error.

Verify NV Overlay Feature Status

show feature | include nv overlay

nv overlay 1 enabled

The output shows that the nv overlay feature is enabled (1 indicates enabled). If disabled, it would show 'disabled'.

Understanding the Output

The 'feature nv overlay' command itself does not produce output beyond the configuration prompt. To verify, use 'show feature' or 'show running-config | include nv overlay'. In 'show feature', the line 'nv overlay 1 enabled' indicates the feature is active.

A healthy state shows 'enabled'; a problem state shows 'disabled' or the feature is missing from the output. If disabled, VXLAN configurations will fail with errors like 'Feature not enabled'.

Configuration Scenarios

Basic VXLAN EVPN Leaf Configuration

Configuring a leaf switch in a VXLAN EVPN fabric. The underlay is OSPF, and the overlay uses BGP EVPN.

Topology

Leaf-1 (Nexus 93180YC-FX3) connected to Spine-1 and Spine-2 via Ethernet1/1 and Ethernet1/2.

Steps

1.Enter global configuration mode.
2.Enable the NV overlay feature.
3.Configure the underlay routing (OSPF).
4.Configure the overlay BGP EVPN.
5.Create NVE interface and VNI.

Configuration

configure terminal
feature nv overlay
feature ospf
router ospf 1
  router-id 10.0.0.1
  network 10.0.0.0/24 area 0
feature bgp
router bgp 65001
  router-id 10.0.0.1
  address-family l2vpn evpn
    neighbor 10.0.0.2 remote-as 65001
    neighbor 10.0.0.2 update-source loopback0
    neighbor 10.0.0.2 address-family l2vpn evpn
interface nve1
  no shutdown
  source-interface loopback0
  member vni 10010
    ingress-replication protocol bgp

Verify: Use 'show feature | include nv overlay' to confirm enabled. Use 'show nve interface nve1' to verify NVE status.

Watch out: Do not forget to enable 'feature nv overlay' before configuring NVE interface; otherwise, the NVE interface command will be rejected.

Troubleshooting with This Command

When troubleshooting VXLAN issues on Nexus switches, the first step is to verify that 'feature nv overlay' is enabled. If it is not, all VXLAN-related commands will fail with errors like '% Invalid command' or 'Feature not enabled'. Use 'show feature' to list all enabled features; look for 'nv overlay 1 enabled'.

If it shows 'disabled', enter global config mode and issue 'feature nv overlay'. If the command is rejected, check the NX-OS version and platform support. For example, older Nexus 7000 switches with M1 line cards do not support VXLAN.

Additionally, if the feature is enabled but VXLAN tunnels are not coming up, check the underlay connectivity and BGP EVPN sessions. The 'show nve peers' and 'show nve vni' commands provide insight into the overlay state. Common issues include misconfigured source interface, incorrect VNI mappings, or MTU mismatches.

Always ensure that the underlay routing is working before troubleshooting the overlay.

CCNA Exam Tips

Remember that 'feature nv overlay' must be enabled before configuring any VXLAN-related commands like 'interface nve1' or 'vni'.

On Nexus switches, the command is 'feature nv overlay', not 'feature vxlan'—a common mistake in exams.

In CCNP Data Center, know that this feature is required for both VXLAN and VXLAN EVPN deployments.

Common Mistakes

Forgetting to enable 'feature nv overlay' before configuring VXLAN, resulting in 'Feature not enabled' errors.

Confusing 'nv overlay' with 'feature vxlan'—the correct command is 'feature nv overlay' on NX-OS.

Not saving the configuration after enabling the feature, causing loss after reload.

feature nv overlay vs feature vn-segment-vlan-based

These two commands are both required for VLAN-based VXLAN segmentation, but they operate at different layers: feature nv overlay enables the underlying overlay infrastructure, while feature vn-segment-vlan-based enables the specific VLAN-to-VNI mapping mechanism. They are often confused because both must be configured for VXLAN with VLAN-based segmentation.

Aspect	feature nv overlay	feature vn-segment-vlan-based
Scope	Enables the entire overlay feature set	Enables VLAN-based VN segment mapping only
Prerequisite	Must be configured before any overlay features	Requires 'feature nv overlay' to be enabled first
Impact on forwarding	Enables overlay packet processing in hardware/software	Allows VLAN-to-VNI mapping; does not directly affect forwarding
Typical use	Always needed for VXLAN or OTV; broad enable	Only used when mapping VLANs to VNIs; not for MAC-based or other segmentation
Dependency on hardware	May require specific line cards or licensing	Requires 'feature nv overlay' and supported hardware

Use feature nv overlay when you need to enable any overlay technology (VXLAN, OTV) on the switch, as it is the master enable for all overlay features.

Use feature vn-segment-vlan-based when you need to map VLANs to VXLAN VNIs, enabling traditional VLAN-based VXLAN segmentation.

Platform Notes

On Cisco Nexus switches, the command 'feature nv overlay' is specific to NX-OS. In contrast, Cisco IOS-XE (e.g., Catalyst 9000) uses 'feature vxlan' or 'l2vpn vfi context' for similar functionality. On Nexus, there is no separate 'feature vxlan'; the NV overlay feature encompasses VXLAN.

For EVPN, additional features like 'feature bgp' and 'nv overlay evpn' are required. Version differences: On NX-OS releases prior to 6.1(2)I2(1), VXLAN was not supported. On Nexus 9000, the feature is available from NX-OS 7.0(3)I1(1) onwards.

On Nexus 3000, VXLAN support is limited to specific models. Always consult the release notes for your platform.

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