SD-WAN Edge shows an ARP entry of 0.0.0.0 under a routed interface

Products

• VMware
• VMware SD-WAN by VeloCloud

Issue/Introduction

Symptoms:

Remote Diagnostics shows a persistent 0.0.0.0 ARP entry pointing to a routed interface configured with no Default Gateway IP.

The entry remains ALIVE and is never removed as long as there is a device connected to it.

This entry is not observed on routed interfaces with a Gateway IP configured.

Example:

 

Environment

VMware SD-WAN
VMware SD-WAN by VeloCloud

Resolution

This is a expected behavior, no action is required. When a routed interface is configured without a default gateway, it sets a "no interface ARP" flag. As a result, the static ARP entry is never removed from the ARP cache for the routed interface.

In versions 4.3 and 4.5 since no default gateway in configured for the routed interface, a static ARP entry is created and no periodic check is enabled. As a result, the static ARP entry is never removed.
In 5.x releases, such static ARP entry is not observed because the "no interface ARP" flag was removed when IPv4 gateway is not configured on a routed interface.