vCloud Director relies on NSX network virtualization platform to provide on-demand creation and management of networks and networking services. NSX for vSphere has been supported for long time and vCloud Director allows most of its feature to be used by its tenants. However as VMware slowly shifts away from NSX for vSphere and pushes forward modern, fully rewritten NSX-T networking platform, I want to focus in this article on its integration with vCloud Director.
Let me start with highlighting that NSX-T is evolving very quickly. It means each release (now at version 2.5) adds major new functionality. Contrast that with NSX-V which is essentially feature complete in a sense that no major functionality change is happening there. The fast pace of NSX-T development is a challenge for any cloud management platforms as they have to play the catch up game.
The first release of vCloud Director that supported NSX-T was 9.5. It supported only NSX-T version 2.3 and the integration was very basic. All vCloud Director could do was to import NSX-T overlay logical segments (virtual networks) created manually by system administrator. These networks were imported into a specific tenant Org VDC as Org VDC networks.
The next version of vCloud Director – 9.7 supported only NSX-T 2.4 and from the feature perspective not much had changed. You could still only import networks. Under the hood the integration however used completely new set of NSX-T policy based APIs and there were some minor UI improvements in registering NSX-T Manager.
The current vCloud Director version 10 for the first time brings on-demand creation of NSX-T based networks and network services. NSX-T version 2.5 is required.
While I do not want to go too deep into the actual NSX-T architecture I fully expect that not all readers of this blog are fully familiar with NSX-T and how it differs from NSX-V. Let me quickly highlight major points that are relevant for topic of this blog post.
- NSX-T is vCenter Server independent, which means it scales independently from vCenter domain. NSX-T essentially communicates with ESXi hosts directly (they are called host transport nodes). The hosts must be prepared with NSX-T vibs that are incompatible with NSX-V which means a particular host cannot be used by NSX-V and NSX-T at the same time.
- Overlay virtual networks use Geneve encapsulation protocol which is incompatible with VXLAN. The concept of Controller cluster that keeps state and transport zone is very similar to NSX-V. The independence from VC mentioned in the previous point means vSphere distributed switch cannot be used, instead NSX-T brings its own N-VDS switch. It also means that there is concept of underlay (VLAN) networks managed by NSX-T. All overlay and underlay networks managed by NSX-T are called logical segments.
- Networking services (such as routing, NATing, firewalling, DNS, DHCP, VPN, load balancing) are provided by Tier-0 or Tier-1 Gateways that are functionally similar to NSX-V ESGs but are not instantiated in dedicated VMs. Instead they are services running on shared Edge Cluster. The meaning of Edge Cluster is very different from the usage in NSX-V context. Edge Cluster is not a vSphere cluster, instead it is cluster of Edge Transport Nodes where each Edge Node is VM or bare metal host.
- While T0 and T1 Gateways are similar they are not identical, and each has specific purpose or set of services it can offer. Distributed routing is implicitly provided by the platform unless a stateful networking service requires routing through single point. T1 GWs are usually connected to single T0 GW and that connection is managed automatically by NSX-T.
- Typically you would have one or small number of T0 GWs in ECMP mode providing North-south routing (concept of Provider Edge) and large number of T1 GWs connected to T0 GW, each for a different tenant to provide tenant networking (concept of Tenant Edge).
vCloud Director Integration
As mentioned above since NSX-T is not vCenter Server dependent, it is attached to vCloud Director independently from VC.
(Geneve) network pool creation is the same as with VXLAN – you provide mapping to an existing NSX-T overlay transport zone.
‘Now you can create Provider VDC (PVDC) which is as usual mapped to a vSphere cluster or resource pool. A particular cluster used by PVDC must be prepared for NSX-V or NSX-T and all clusters must share the same NSX flavor. It means you cannot mix NSX-V clusters with NSX-T in the same PVDC. However you can easily share NSX-V and NSX-T in the same vCenter Server, you will then just have to create multiple PVDCs. Although NSX-T can span VCs, PVDC cannot – that limitation still remains. When creating NSX-T backed PVDC you will have to specify the Geneve Network Pool created in the previous step.
Within PVDC you can start creating Org VDCs for your tenants – no difference there.
Org VDCs without routable networks are not very useful. To remedy this we must create external networks and Org VDC Edge Gateways. Here the concept quite differs from NSX-V. Although you could deploy provider ECMP Edges with NSX-V as well (and I described here how to do so), it is mandatory with NSX-T. You will have to pre-create T0 GW in NSX-T Manager (ECMP active – active is recommended). This T0 GW will provide external networking access for your tenants and should be routable from the internet. Instead of just importing external network port group how you would do with NSX-V you will import the whole T0 GW in vCloud Director.
During the import you will also have to specify IP subnets and pools that the T0 GW can use for IP sub-allocation to tenants.
Once the external network exist you can create tenant Org VDC Edge Gateways. These will be T1 GWs instantiations into the same NSX-T Edge Cluster as the T0 GW they connect to. Currently you cannot chose different NSX-T Edge Cluster for their placement. T1 GWs are always deployed in Active x Standby configuration, the placement of active node is automated by NSX-T. The router interlink between T0 and T1 GWs is also created automatically by NSX-T.
During the Org VDC Edge Gateway the service providers also sub-allocates range of IPs from the external network. Whereas with NSX-V these would actually be assigned to the Org VDC Edge Gateway uplink, this is not the case with NSX-T. Once they are actually used in a specific T1 NAT rule, NSX-T will automatically create static route on the T0 GW and start routing to the correct T1 GW.
There are four types of NSX-T based Org VDC networks and three of them are available to be created via UI:
- Isolated: Layer 2 segment not connected to T1 GW. DHCP service is not available on this network (contrary to NSX-V implementation).
- Routed: Network that is connected to T1 GW. Note however that its subnet is not announced to upstream T0 GW which means only way to route to it is to use NAT.
- Imported: Existing NSX-T overlay logical segment can be imported (same as in VCD 9.7 or 9.5). Its routing/external connectivity must be managed outside of vCloud Director.
- In OpenAPI (POST /1.0.0/OrgVdcNetwork) you will find one more network type: DIRECT_UPLINK. This is for a specific NFV use case. Such network is connected directly to T0 GW with external interface. Note this feature is not officially supported!
Note that only Isolated and NAT-routed networks can be created by tenants.
As you can see it is not possible today to create routed advertised Org VDC network (for example for direct connect use case when tenant wants to route from on-prem networks to the cloud without using NAT). These routed networks would require dedicated T0 GW for each tenant which would not scale well but might be possible in the future with VRF support on T0 GWs.
Tenant Networking Services
Currently the following T1 GW networking services are available to tenants:
- DHCP (without binding and relay)
- DNS forwarding
- IPSec VPN: No UI, OpenAPI only. Policy
and routebased with pre share key is supported. (Thanks Abhi for the correction).
All other services are currently not supported. This might be due to NSX-T not having them implemented yet, or vCloud Director not catching up yet. Expect big progress here with each new vCloud Director and NSX-T release.
All NSX-T related features are available in the vCloud Director OpenAPI (CloudAPI). The pass through API approach that you might be familiar with from the Advanced Networking NSX-V implementation is not used!
I have summarized all vCloud Director networking features in the following table for quick comparison between NSX-V and NSX-T.