Communication over Edge VLAN uplink/service interface fails if the Edge node has multiple interfaces of the same VLAN

Products

• VMware NSX

Issue/Introduction

• Communication over Edge VLAN uplink/service interface fails.
• You see multiple uplink/service interfaces are configured on an Edge node.
  
  • You can check it by get logical-router interfaces .
    

    interface   : <UUID>
ifuid       : <NNN>
VRF         : <UUID>
name        : <gateway>
Fwd-mode    : IPV4_ONLY
mode        : lif
port-type   : service
IP/Mask     : <IP/Mask>
MAC         : <MAC address>
VLAN        : <VLAN ID>
LS port     : <UUID>
urpf-mode   : STRICT_MODE
admin       : up
op_state    : up
MTU         : 1500
arp_proxy   :

    
    interface   : <UUID>
ifuid       : <NNN>
VRF         : <UUID>
name        : <gateway>
Fwd-mode    : IPV4_ONLY
mode        : lif
port-type   : service
IP/Mask     : <IP/Mask>
MAC         : <MAC address>
VLAN        : <VLAN ID>
LS port     : <UUID>
urpf-mode   : STRICT_MODE
admin       : up
op_state    : up
MTU         : 1500
arp_proxy   :

• Even if there is currently no VLAN overlap, it is still possible that the Edge node has experienced VLAN overlap.
  In such a case, the VLAN interface left on the Edge node might not be functioning.
  • You can check it by get host-switch vlan-table .
    
    VLAN        : <VLAN ID>
    MAC         : <MAC address>
    Ingress Port
        name        : fp-eth0
        ID          : 0
    Egress Port
        port        : <UUID>
        ifuid       : <NNN>
    
    The interface whose [LS port] matches [Egress Port] - [Port] is functioning.
    If [LS port] does not appear in get host-switch vlan-table , the interface is not functioning.

Environment

VMware NSX-T
VMware NSX

Cause

An Edge node can have only 1 VLAN uplink/service interface per VLAN ID and vNIC.

Since NSX-T 3.1 validation have been implemented to prevent multiple VLAN interfaces of the same VLAN.
However, it's been reported that the validation was somehow slipped through and multiple VLAN interfaces of the same VLAN could be configured on an Edge node.
In such a case, only one of the interfaces works fine.

Resolution

Currently, there is no resolution.

If you find multiple VLAN interfaces of the same VLAN is configured on an Edge node, distribute the gateways to another Edge node.
After you make sure only 1 interfaces of the VLAN is configured on an Edge node, disable/enable the interface to make sure it is functioning.

To prevent such a configuration, if you plan to configure multiple interfaces of the same VLAN within an Edge cluster, first distribute gateways and make sure the gateways do not share the same Edge node, and then create VLAN interfaces.