DLR ARP traffic is not suppressed as expected in NSX

Products

• VMware NSX

Issue/Introduction

Symptoms:

• DLR ARP Suppression may not be effective under some conditions which can result in a larger volume of ARP traffic than expected.
• ARP traffic sent by a DLR will not be suppressed if an ESXi host has more than one active port connected to the destination VNI, for example the DLR port and one or more VM vNICs.
• DLR ARP suppression works as expected if there is only one active port i.e. the DLR port, connected to the destination VXLAN network.

Environment

VMware NSX for vSphere 6.2.x
VMware NSX for vSphere 6.3.x

Cause

NSX 6.2.4 introduced ARP Suppression for DLR ARP traffic. ARP Suppression leverages the NSX Controllers to reduces the amount of ARP traffic generated by the DLR.

Resolution

This issue is resolved in VMware NSX for vSphere 6.4.0, available at VMware Downloads.

Workaround:
To work around this issue if you do not want to upgrade:

• Navigate to VMware vSphere Web Client  > Networking.
• Click Edit Settings on the Logical Switch port group.
• Select VLAN.
• Change the VLAN type to None.
• Click OK.

Notes:

• If applying this workaround in an environment with vDS Healthcheck enabled, be aware false positive vDS Healthcheck alarms may be triggered. For more information, see vSphere Distributed Switch Healthcheck alarms triggered in an NSX for vSphere 6.4.0 environment (53724).
• Applying the workaround does not disrupt the data plane forwarding.
• The workaround must not be applied to Logical Switches set for "guestVlanAllowed".