IPv6 address populated for router links even when the forwarding mode is set to 'IPv4 only'

Products

• VMware NSX

Issue/Introduction

• L3 forwarding mode is set to 'IPv4 only' under global networking config.
  
  
  
• Only IPv4 address is configured under T0-T1 transit subnets in Tier-0.
  
  
• IPv6 address is observed to be auto populated under router link for Tier-0 and Tier-1.
  

Environment

VMware NSX

Cause

When the L3 forwarding mode is set to IPv4 only, the system automatically sets the status of these assigned IPv6 addresses to 'not active (NA)'. The presence of the address in the configuration or UI does not indicate that IPv6 routing is functional or enabled for data plane traffic.

Resolution

No action is required as this is a cosmetic/configurational default. The operational state is governed by the L3 Forwarding Mode:

• When L3 forwarding mode is set to 'IPv4 only':

  • IPv6 addresses are assigned but remain in a 'not active' state.

  • IPv6 traffic is not forwarded by the gateways.

• When L3 forwarding mode is set to 'IPv4 and IPv6':

  • IPv6 addresses become active.

  • The gateways will process and forward IPv6 traffic according to the configured routing policies.

Additional Information

Reference:Configure IPv6 Layer 3 Forwarding