You can add GRE (Generic Routing Encapsulation) tunnels for NSX tier-0 and tier-0 VRF gateways to connect on-premises and cloud networks.

GRE tunnels are stateless and are supported with the following:

  • Active-standby edge clusters
  • Active-active stateless
  • Static routes
  • BGP
  • BFD
  • IPv4 and IPv6 workloads

There are some limitations for the GRE functionality in NSX:

  • No layer 4 through layer 7 services.
  • GRE cannot be configured on an active-active stateful gateway.
  • Multicast over GRE is not supported.
  • NSX Federation is not supported.
  • OSPF (Open Shortest Path First) over GRE is not supported.
  • IPv6 addresses cannot be used for outer IP addresses of the GRE tunnel (source and destination IP addresses).
  • PMTU discovery and MTU updates are not supported.
  • TCP MSS clamping is not supported.


For the tier-0 or tier-0 VRF gateway, ensure that:

  • Either external or loopback interfaces are configured as the tunnel source IP address (local endpoint).
  • Routing is configured for reachability between the GRE remote endpoints.
  • For BGP over GRE configuration, ensure that proper filters are installed on the BGP neighbor over GRE. Remote endpoint network should not be learned over this session. Otherwise, it results in a routing loop.


  1. With admin privileges, log in to NSX Manager.
  2. Select Networking > Tier-0 Gateways.
  3. Expand the Interfaces and GRE Tunnels category.
  4. For GRE Tunnels, click Set and then Add GRE Tunnel.
  5. Enter a name for the GRE tunnel.
  6. Click Set for Tunnel Addresses and configure the tunnel addresses:
    1. Click Add Tunnel Address.
    2. Select an edge node.
    3. Select the source IP address.
    4. Enter the subnets.
    5. Click Add and then Apply.
  7. Enter the destination IP address.
  8. (Optional) Configure the keepalive settings:
    1. Use the Keep Alive toggle to enable or disable keepalive signals to be periodically sent to the remote endpoint.

      Keepalive signals are used to check the health of the connection between the GRE tunnel and gateway and whether the GRE tunnel should remain up.

    2. Use the Keep Alive Ack toggle to enable or disable keepalive packets to be sent back to their source endpoint.

      After the decapsulation of incoming keepalive packets, the edge datapath sends back the keepalive packets to the source endpoint. This setting is enabled by default.

    3. Use the Dead Multiplier field to specify the number of consecutive failures or times when the keepalive is not received before making the GRE tunnel to go down.
      Note: The minimum is 3 and the maximum is 5.
    4. Use the Keep Alive Timer field to specify the number of seconds for the intervals at which keepalives are sent.
      Note: The minimum is 2 and the maximum is 120.
  9. Click Save.
  10. (Optional) After the GRE tunnel is created, you can view statistics for the GRE tunnel:
    1. Click Tunnel Statistics to view a summary of the received and transmitted traffic.
    2. Click Keep Alive Statistics to view the details of the keepalive signals and keepalive ack.
    3. Click Tunnel Connectivity Status to view the connectivity related information.
      Note: To display the Last Up Time and Last Down Time data, the Keep Alive and Keep Alive Ack toggles must be enabled.