Horizontal Solution Scale

Horizontal Solution Scale

The Cisco SD-WAN solution is highly scalable, beginning at the controller level. You can cluster Cisco vManage devices to the levels required and add Cisco vBond orchestrators and Cisco vSmart controllers.

You need to connect each WAN Edge router to at least two Cisco vSmart controllers. If Cisco vSmart controllers reach their limits, simply add more controllers and balance the WAN Edge routers between them.

Some scaling numbers for the control plane are as follows:

Cisco vBond maintains persistent connections with each active vManage and each Cisco vSmart. WAN Edge routers initially connect to the vBond, but the connection is transient once permanent connections are made to Cisco vManage and Cisco vSmart controllers. Each Cisco vBond supports up to 4000 connections, and up to eight Cisco vBond orchestrators have been tested in a single Cisco SD-WAN domain. Estimate one Cisco vBond for every 2000 WAN Edge routers. Cisco vBond can be oversubscribed to simplify the scaling requirements, since the WAN Edge router connections to Cisco vBond are transient. Additional Cisco vBond orchestrators should be added for sufficient redundancy.

Cisco vSmart maintains a persistent connection to each active Cisco vManage and every other Cisco vSmart. Each Cisco vSmart maintains a persistent connection with each Cisco vBond. WAN Edge routers persistently connect to two Cisco vSmart controllers by default over each transport. Each Cisco vSmart supports up to 5200 DTLS connections for each controller, and up to 12 controllers have been tested in a high availability environment. Each vSmart also supports up to 2600 OMP sessions and 256K routes. Estimate one Cisco vSmart for every 2000 WAN Edge devices. For most deployments, two Cisco vSmart controllers for redundancy are sufficient. You can deploy additional controllers in larger deployments and use the affinity feature to distribute control connections to the WAN Edge routers.

Cisco vManage maintains a persistent connection to each Cisco vSmart and every other active Cisco vManage. Each Cisco vManage maintains a persistent connection with each Cisco vBond. Up to six vManage servers have been tested in a single cluster. Backup Cisco vManage servers or Cisco vManage clusters can be added to ensure sufficient redundancy. Note that the number of devices a Cisco vManage can support can vary depending on several factors, such as the number of statistics and flows that might be generated. Therefore, depending on the network demands, you might need to add extra Cisco vManage nodes.

Scalability numbers vary depending on the software version and enabled features. For the latest scalability information, see the Cisco SD-WAN Controller Compatibility Matrix and Recommended Computing Resources document.

Using Affinity to Manage Network Scaling

In the Cisco SD-WAN overlay network, all WAN Edge routers establish control connections to all Cisco vSmart controllers to help ensure that the routers can properly route data traffic across the network. As networks increase in size, with routers at thousands of sites and Cisco vSmart controllers in multiple data centers managing the flow of control and data traffic among routers, network operation can be improved by limiting the number of Cisco vSmart controllers that a router can connect to. When data centers are distributed across a broad geography, network operation can also be better managed by having routers establish control connections only with Cisco vSmart controllers collocated in the same geographic region.

Establishing affinity between Cisco vSmart controllers and WAN Edge routers will allow you to control the scaling of the overlay network by limiting the number of Cisco vSmart controllers with which a WAN Edge router can establish control connections and establish transport locations (TLOCs). Affinity allows you to distribute the WAN Edge control connections across Cisco vSmart controllers when you have redundant routers in a single data center. Similarly, when you have multiple data centers in the overlay network, affinity allows you to distribute the WAN Edge control connections across the data centers. With affinity, you can also define primary and backup control connections to maintain overlay network operation in case the connection to a single Cisco vSmart controller or to a single data center fails.