Viptela SDWAN Overview
29th June 2018
Viptela is an SDWAN company that was recently purchased by Cisco. In this post I will go over the components that make up the Viptela secure extensible network (SEN) solution. By the end of this post you will have a good idea of the pieces that make up the Viptela puzzle.
The underlay network is made up of your traditional transport networks such MPLS, broadband and 4G internet. The Viptela solution hitches a ride on top of the underlay network.
The overlay network is a virtual IP fabric built on top of the underlay transport using IPsec tunnels. The fabric can be either full mesh, partial mesh or hub and spoke topologies.
Viptela has references to two types of VPN's which can be a little confusing unless you know the distinction between the two.
- Transport side VPNs use IPSEC to encrypt the WAN underlay transport.
- Service side VPNs are LAN side VPNs which are similar to an MPLS L3VPN.
Viptela uses a concept similar to MPLS L3VPNs to build network wide LAN segmentation. These segments are called service side vpns which are separate VRF domains. Service side VPNs allow an administrator to define polices that logically splits groups of users and or applications into separate routing domains.
When you become a Viptela customer they assign your company a unique organization name. The vEdges you purchase are assigned to your organization for the purpose of support, certificate lifecycle and zero touch provisioning.
Mutual authentication is performed using PKI certificates. The beauty of the Viptela solution is that the certificate life-cycle is managed for you so the administrative burden of managing a certificate infrastructure is shouldered by Viptela. Of course if organizational policy demands the certificates are managed in house, this is also possible.
Each Viptela device is assigned a unique system IP. The system IP is similar to a router-id under a routing process. It is used to identify the device but does not need to be injected into any routing protocol.
The Viptela solution has a robust configuration management engine allowing you to define configuration templates for your devices ensuring a consistent configuration is applied across the entire fleet. It is also possible to configure the devices via a CLI if you get nostalgic.
Zero touch provisioning is one of the killer features of the Viptela solution. Not only does it support ZTP the ZTP solution actually works reliably (More on this later).
Z Plane, Z Plane
The Viptela solution maintains complete separation of the control plane and the data plane. Both planes utilize tunneling protocols to ensure secure information exchange.
The Viptela control plane utilizes either UDP/DTLS or TCP/TLS protocols to encrypt control plane traffic. Viptela invented the proprietary overlay management protocol (OMP) to exchange messages and also act as the control plane for IPSEC.
Data payloads are exchanged between vEdges over an encrypted IPSEC transport. IPSEC tunnels are built using public key authentication relieving the need to painfully manage pre-shared keys. IPSEC tunnels are only built between vEdge devices.
The Viptela devices can be managed centrally, via the CLI or a combination of both. Each Viptela device has a default management VPN (similar to a service side VPN) which enables out of band connectivity and cannot be removed.
The controller stack is made up of three types of devices that can either be hosted by Viptela in the cloud or on the customers premises.
The vManage NMS is the central point of device management and monitoring for the Viptela solution. Everything from device configuration templates to routing policy is defined on the vManage. The vManage can also acts as an intermediate certificate authority providing certificate signing services for cloud vEdge devices. The vManage maintains a permanent control plane connection to all Viptela devices in the overlay network for monitoring and configuration purposes. The vManage also has a full featured API allowing configuration and monitoring through a programmable interface.
The vBond orchestrator is the connectivity coordinator for the Viptela solution. The vBond typically sits in an internet facing security zone and has 3 main functions.
- Validate and authenticate devices that join the overlay network.
- Act as a NAT traversal facilitator between vSmarts and vEdges behind NAT devices.
- Load balances vEdge devices across multiple vSmarts in environments with multiple vSmarts.
The vSmart controller is the central point of policy control in the overlay network and has the following main functions.
- Maintains a permanent control plane connection to vEdge devices in order to pass routing information.
- Uses OMP to advertise routing information to vEdge devices in a similar manner to BGP route reflectors.
- Acts as an IPSEC key reflector passing encryption key information between vEdges.
- Enforces routing policy to control routing advertisements and enforce network wide segmentation.
vEdge routers are either physical or virtual devices that are responsible for sending data plane traffic across the network. vEdges create IPSEC VPN tunnels between each other which form the virtual IP fabric. Hardware vEdges have a "trusted board chip" that contain the routers public and private keys as well as a signed certificate. This allows them to connect to the overlay network securely via ZTP or by applying a minimal configuration.
How Does It All Come Together
Now that we understand the components in the Viptela solution, lets have a look at how it might look in a example scenario.
Consider the below network, the environment consists of a primary and secondary data center, a cloud provider, a campus network and N number of remote offices. These locations are connected via multiple WAN transport technologies such as MPLS, broadband, 4G and private interconnects to a could provider.
The controler stack can either be hosted by Viptela in the cloud or in an on premises data centre. Control plane connections are formed between the vManage, vSmart, vBond and the vEdges devices. By default a permanent control plane connection will be established to the vManage and vSmart over each transport side link.
Data plane connections are only formed between the vEdges. You can see from the diagram that the data plane is not established with the vManage, vBond or vSmart controllers further illustrating the point around complete separation of the control and data planes. By default, vEdges will attempt to form an IPSEC tunnel with every other vEdge across every link on each device. This kind of full mesh results in ALOT of overhead just managing and maintaining IPSEC. It is recommended to use policy to limit the topology to hub and spoke, partial mesh or something in between that makes sense to the business requirements.
All Together Now
When you put it all together you can see why Viptela calls it a virtual IP fabric.
How Does ZTP Work
Zero touch provisioning (ZTP) is one of the best features of the Viptela solution so I want to spend a bit of time going over it. I am not really a fan of the term ZTP because in reality it's more like low touch provisioning (LTP). Nevertheless the Viptela solution actually delivers on the promise of making deployments simple and secure by default with very little overhead required by the administrator.
To use the ZTP service, there are a number of things that need to be completed. At a high level they are as follows.
- The controller stack (vManage, vBond and vSmart) need to be configured.
- The vBond requires a publicly resolvable DNS record.
- Raise a case with Viptela asking them to point the ZTP service to your organizations vBond.
- vEdges need to be placed in an authorized state in the vManage and have a configuration template assigned.
- vEdges require a WAN IP and DNS servers to be assigned via DHCP and access to the internet.
Physical vEdges come pre-configured with a few settings that help facilitate the ZTP process. The vEdge has a WAN port configured as a DHCP client and tunnel configuration enabled. They are pre-configured to use ztp.viptela.com as their vBond. As part of the procurement process the vEdges chassis ID and serial number are assigned to a customers organization. The below diagram illustrates the ZTP process.
- WAN IP address and DNS servers are assigned via DHCP.
- vEdge contacts ztp.viptela.com with its chassis ID and serial number.
- ztp.viptela.com advises the vEdge of its organizations vBond public DNS name.
- vEdge contacts its organizations vBond with its chassis ID and serial number.
- vBond advised the vEdge of its organizations vManage IP address.
- vEdge contacts the vManage with its chassis ID and serial number.
- vManage advises the vEdge of its configuration, at this point the vEdge tears down its control plane connections and reconnects starting at step 4 this time using the system IP that was applied via the configuration from the vManage.
- vEdge joins the overlay network and can participate in data plane exchange with other vEdge devices.
There are a number of moving parts, but once setup correctly if the WAN link is plugged into the correct port on the vEdge then the deployment process is simple and works very well. In my experience only a very small number of vEdge deployments require an administrator to intervene.
After using the Viptela product for around a year and a half it's easy to see why Cisco purchased them. Viptela has redefined how you configure and manage your WAN making it simple and secure by default. You should now have a better idea of what components make up the Viptela SDWAN solution.