vBond Orchestrator Redundancy
The vBond orchestrator performs two key functions in the Cisco SD-WAN overlay network:
Authenticates and validates all vSmart controllers and routers that attempt to join the Cisco SD-WAN network.
Orchestrates the control plane connections between the vSmart controllers and routers, thus enabling vSmart controllers and routers to connect to each other in the Cisco SD-WAN network.
The vBond orchestrator runs as a VM on a network server. The vBond orchestrator can also run on a router that is configured to be a vBond orchestrator, however this is not recommended, and it limits the number of router control connections to 50. If using running the vBond daemon on a router, note that only one vBond daemon can run at a time on a router, so to provide redundancy and high availability, the network must have two or more routers that function as vBond orchestrators. (Note also that it is not recommended to use a router acting as a vBond orchestrator as a regular router.)
Having multiple vBond orchestrators ensures that one of them is always available whenever a Cisco device such as a router or a vSmart controller is attempting to join the network.
Configuration of Redundant vBond Orchestrators
A router learns that it is acting as a vBond orchestrator from its configuration. In the system vbond configuration command, which defines the IP address (or addresses) of the vBond orchestrator (or orchestrators) in the Cisco SD-WAN overlay network, you include the local option. In this command, you also include the local public IP address of the vBond orchestrator. (Even though on Cisco vEdge device and vSmart controllers you can specify an IP address of vBond orchestrator as a DNS name, on the vBond orchestrator itself, you must specify it as an IP address.)
On vSmart controllers and Cisco vEdge devices, when the network has only a single vBond orchestrator, you can configure the location of the vBond system either as an IP address or as the name of a DNS server (such as vbond.cisco.com). (Again, you configure this in the system vbond command.) When the network has two or more vBond orchestrators and they must all be reachable, you should use the name of a DNS server. The DNS server then resolves the name to a single IP address that the vBond orchestrator returns to the Cisco vEdge device. If the DNS name resolves to multiple IP addresses, the vBond orchestrator returns them all to the Cisco vEdge device, and the router tries each address sequentially until it forms a successful connection.
Note that even if your Cisco SD-WAN network has only a single vBond orchestrator, it is recommended as a best practice that you specify a DNS name rather than an IP address in the system vbond configuration command, because this results in a scalable configuration. Then, if you add additional vBond orchestrators to your network, you do not need to change the configurations on any of the routers or vSmart controllers in your network.
Recovering from a vBond Orchestrator Failure
In a network with multiple vBond orchestrators, if one of them fails, the other vBond orchestrators simply continue operating and are able to handle all requests by Cisco devices to join the network. From a control plane point of view, each vBond orchestrator maintains a permanent DTLS connections to each of the vSmart controllers in the network. (Note however, that there are no connections between the vBond orchestrators themselves.) As long as one vBond orchestrator is present in the domain, the Cisco SD-WAN network is able to continue operating without interruption, because vSmart controllers and routers are still able to locate each other and join the network.
Because vBond orchestrators never participate in the data plane of the overlay network, the failure of any vBond orchestrator has no impact on data traffic. vBond orchestrators communicate with routers only when the routers are first joining the network. The joining router establishes a transient DTLS connection with a vBond orchestrator to learn the IP address of a vSmart controller. When the Cisco vEdge device configuration lists the vBond address as a DNS name, the router tries each of the vBond orchestrators in the list, one by one, until it is able to establish a DTLS connection. This mechanism allows a router to always be able to join the network, even after one of a group of vBond orchestrators has failed.