Add a Tier-0 Gateway from Global Manager

You can add a tier-0 gateway from the Global Manager. This gateway can have a span of one or more locations. This span affects the span of the tier-1 gateways and sengments attached to it.

For details about tier-0 gateway configurations in NSX Federation, refer to Tier-0 Gateway Configurations in NSX Federation.

The following settings must be kept consistent across locations. If you change these settings from the Global Manager web interface, those changes are automatically applied on all locations. However, if you change these settings using the API, you must manually make the same changes in each location.

Local AS
ECMP settings
Multipath Relax settings
Graceful Restart

Important:

When you create a tier-0 gateway from Global Manager, you must configure an external interface in each location that the tier-0 is stretched to. Each external interface must be connected to a segment that was created from Global Manager, with the Connectivity set to None and the Traffic type set to VLAN. Refer to Add a Segment from Global Manager. The Edge nodes configured with those external interfaces are used for inter-location communication, even if northbound communication is not needed.

Prerequisites

If you are creating a tier-0 gateway that spans more than one location, verify that each location has Edge nodes configured with RTEPs for stretched networking. Refer to Configure Edge Nodes for Stretched Networking.
If you plan to configure the gateway DHCP server, refer to Attach an NSX DHCP Profile to a Tier-0 or Tier-1 Gateway.

Procedure

From your browser, log in with admin privileges to the active Global Manager at https://<global-manager-ip-address>.
Select Networking > Tier-0 Gateways.
Enter a name for the gateway.
Select an HA (high availability) mode to configure within each location.

The default mode is active-active. In the active-active mode, traffic is load balanced across edge nodes in all locations. In the active-standby mode, an elected Edge node processes traffic in each location. If the active node fails, the standby node becomes active.

If the HA mode is active-standby, select a failover mode.


Option	Description
Preemptive	If the preferred node fails and recovers, it will preempt its peer and become the active node. The peer will change its state to standby.
Non-preemptive	If the preferred node fails and recovers, it will check if its peer is the active node. If so, the preferred node will not preempt its peer and will be the standby node.

(Optional) Add DHCP Config on the gateway.

Specify the span of this tier-0 gateway by providing the following details for each location. To add additional locations, click Add Location.

Option	Description
Location	Select the location from the drop-down menu.
Edge Cluster	Select an Edge cluster from this location. If you are configuring a stretched tier-0, you must select an Edge cluster that contains Edge nodes that are configured with an RTEP.
Mode	Each location of the tier-0 gateway can have a mode of Primary or Secondary. If the HA mode is Active Active, you can configure the tier-0 gateway with all locations mode set to primary. Select the Mark all locations as Primary toggle to mark all locations as primary. If the HA mode is Active Active or Active Standby, you can configure the tier-0 gateway with one location set to Primary, and all others set to Secondary. Select Primary mode for one location. In all other locations, set mode to Secondary. For secondary locations, you must select a fallback preference.

Click Additional Settings.
1. In the Internal Transit Subnet field, enter a subnet.
  This is the subnet used for communication between components within this gateway. The default is 169.254.0.0/24.
2. In the T0-T1 Transit Subnets field, enter one or more subnets.
  These subnets are used for communication between this gateway and all tier-1 gateways that are linked to it. After you create this gateway and link a tier-1 gateway to it, you will see the actual IP address assigned to the link on the tier-0 gateway side and on the tier-1 gateway side. The address is displayed in Additional Settings > Router Links on the tier-0 gateway page and the tier-1 gateway page. The default is 100.64.0.0/16.
  After the tier-0 gateway is created, you can change the T0-T1 Transit Subnets by editing the gateway. Note that this will cause a brief disruption in traffic.
3. In the Intersite Transit Subnet field, enter a subnet. This subnet is used for cross-location communication between gateway components. The default is 169.254.32.0/20.
Click Save.
To configure interfaces, expand the Interfaces and GRE Tunnels category and click Set or the hyperlinked number for External and Service Interfaces. Configure an external interface for each location that the tier-0 gateway spans.
1. Click Add Interface.
2. Enter a name.
3. Select a location.
4. Select a type.
  If the HA mode is active-standby, the choices are External, Service, and Loopback. If the HA mode is active-active, the choices are External and Loopback.
  
  Service interfaces are supported only on gateways that span one location. If the gateway is stretched, service interfaces are not supported.
5. Enter an IP address in CIDR format.
6. Select a segment.
  The segment must be created from the Global Manager, with the Connectivity set to None and the Traffic type set to VLAN. See Add a Segment from Global Manager.
7. If the interface type is not Service, select an NSX Edge node.
8. (Optional) If the interface type is not Loopback, enter an MTU value.
9. Skip PIM configuration.
  Multicast is not supported in NSX Federation.
10. (Optional) Add tags and select an ND profile.
11. (Optional) If the interface type is External, for URPF Mode, you can select Strict or None.
  Asymmetric routing or forwarding is not recommended. Therefore, URPF Mode is set to Strict by default.
  For symmetric routing, ensure that the configuration between tier-0 gateway and northbound routers is such that the same set of prefixes are advertised from each edge node within a tier-0 gateway on a given site. Also, the same set of prefixes must be learned from TORs on all edge nodes of a tier-0 gateway on a given site.
  
  If you have BGP between the tier-0 gateway and northbound routers and you are using route-maps or filters, ensure that this configuration is consistent for inbound and outbound directions for all edge nodes.
  
  For a federation environment with primary and secondary sites, you should advertise longer AS paths for BGP advertisements on secondary site BGP neighbors to resolve asymmetric forwarding.
  
  If there is a need for asymmetric routing, set URPF Mode to None.
12. (Optional) After you create an interface, you can download the aggregate of ARP proxies for the gateway by clicking the menu icon (three dots) for the interface and selecting Download ARP Proxies.
  
  You can also download the ARP proxy for a specific interface by expanding a gateway and then expanding Interfaces. Click an interface and click the menu icon (three dots) and select Download ARP Proxy.
  
  Note: You cannot download the ARP proxy for loopback interfaces.
Click Routing to add IP prefix lists, community lists, static routes, and route maps.

When you add a static route on a tier-0 gateway, the default behavior is that the static routes are pushed to all locations configured on the gateway. However, the routes are enabled only on the primary locations. This ensures that on the secondary locations, the routes that are learned from the primary location are preferred.

If you want to change this behavior, you can use the Enabled on Secondary setting and the Scope setting.

If you select Enabled on Secondary, the static route is also enabled on the secondary locations.

When you add a next hop for a static route, you can set the Scope. The scope can be an interface, a gateway, or a segment. On a tier-0 gateway created from Global Manager, the scope can also be a location. You can use the scope setting to configure different next hops for each location.
Click BGP to configure BGP.

When you configure BGP on a tier-0 gateway from the Global Manager, most settings apply to all locations.

Some of the settings within the BGP configuration, such as Route Aggregation and BGP Neighbors prompt you to provide separate values for each location.

See Configure BGP for more information about configuring BGP.
To configure route redistribution, click Route Redistribution, and for each location, click Set.
Select one or more of the sources:
- Tier-0 subnets: Static Routes, NAT IP, IPsec Local IP, DNS Forwarder IP, Router Link, Connected Interfaces & Segments.
  Under Connected Interfaces & Segments, you can select one or more of the following: Service Interface Subnet, External Interface Subnet, Loopback Interface Subnet, Connected Segment.
- Tier-0 subnets: Static Routes, NAT IP, IPsec Local IP, DNS Forwarder IP, EVPN TEP IP, Connected Interfaces & Segments.
  Under Connected Interfaces & Segments, you can select one or more of the following: Service Interface Subnet, External Interface Subnet, Loopback Interface Subnet, Connected Segment.
- Advertised tier-1 subnets: DNS Forwarder IP, Static Routes, LB VIP, NAT IP, LB SNAT IP, IPsec Local Endpoint, Connected Interfaces & Segments.
  Under Connected Interfaces & Segments, you can select Service Interface Subnet and/or Connected Segment.

What to do next

Set up a tier-1 gateway from Global Manager.