High Availability Configuration Guide for vEdge Routers, Cisco SD-WAN Release 20

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Book Title

High Availability Configuration Guide for vEdge Routers, Cisco SD-WAN Release 20

Chapter Title

High Availability Overview

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Updated:
February 8, 2023

Chapter: High Availability Overview

High Availability Overview

The goal of any high availability solution is to ensure that all network services are resilient to failure. Such a solution aims to provide continuous access to network resources by addressing the potential causes of downtime through functionality, design, and best practices. The core of the Cisco SD-WAN high availability solution is achieved through a combination of three factors:

  • Functional hardware device redundancy. The basic strategy consists of installing and provisioning redundant hardware devices and redundant components on the hardware. These devices are connected by a secure control plane mesh of Datagram Transport Layer Security (DTLS) connections among themselves, which allows for rapid failover should a device fail or otherwise become unavailable. A key feature of the Cisco SD-WAN control plane is that it is established and maintained automatically, by the Cisco vEdge devices and software themselves.

  • Robust network design.

  • Software mechanisms ensure rapid recovery from a failure. To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors the status of all Cisco vEdge devices in the network and automatically adjusts to changes in the topology as devices join and leave the network. For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD), which runs on the secure IPsec tunnels between routers.

​​Recovery from a failure is a function of the time it takes to detect the failure and then repair or recover from it. TheCisco SD-WAN solution provides the ability to control the amount of time to detect a failure in the network. In most cases, repair of the failure is fairly instantaneous.

Hardware Support of High Availability

A standard best practice in any network setup is to install redundant hardware at all levels, including duplicate parallel routers and other systems, redundant fans, power supplies and other hardware components within these devices, and backup network connections. Providing high availability in the Cisco SD-WAN solution is no different. A network design that is resilient in the face of hardware failure should include redundant Cisco vBond Orchestrators, Cisco vSmart Controllers, and routers and any available redundant hardware components.

Recovery from the total failure of a hardware component in the Cisco SD-WAN overlay network happens in basically the same way as in any other network. A backup component has been preconfigured, and it is able to perform all necessary functions by itself.

Robust Network Design

In addition to simple duplication of hardware components, the high availability of a Cisco SD-WAN network can be enhanced by following best practices to design a network that is robust in the face of failure. In one such network design, redundant components are spread around the network as much as possible. Design practices include situating redundant Cisco vBond Orchestrators and Cisco vSmart Controllers at dispersed geographical locations and connecting them to different transport networks. Similarly, the routers at a local site can connect to different transport networks and can reach these networks through different NATs and DMZs.

Software Support of High Availability

The Cisco SD-WAN software support for high availability and resiliency in the face of failure is provided both in the control plane, using the standard DTLS protocol and the proprietary Cisco SD-WAN Overlay Management Protocol (OMP), and in the data plane, using the industry-standard protocols BFD, BGP, OSPF, and VRRP.

Control Plane Software Support of High Availability

The Cisco SD-WAN control plane operates in conjunction with redundant components to ensure that the overlay network remains resilient if one of the components fails. The control plane is built on top of DTLS connections between the Cisco devices, and it is monitored by the Cisco SD-WAN OMP protocol, which establishes peering sessions (similar to BGP peering sessions) between pairs of vSmart controllers and routers, and between pairs of vSmart controllers. These peering sessions allow OMP to monitor the status of the Cisco devices and to share the information among them so that each device in the network has a consistent view of the overlay network. The exchange of control plane information over OMP peering sessions is a key piece in the Cisco SD-WAN high availability solution:

  • vSmart controllers quickly and automatically learn when a vBond orchestrator or a router joins or leaves the network. They can then rapidly make the necessary modifications in the route information that they send to the routers.

  • vBond orchestrators quickly and automatically learn when a device joins the network and when a vSmart controller leaves the network. They can then rapidly make the necessary changes to the list of vSmart controller IP addresses that they send to routers joining the network.

  • vBond orchestrators learn when a domain has multiple vSmart controllers and can then provide multiple vSmart controller addresses to routers joining the network.

  • vSmart controllers learn about the presence of other vSmart controllers, and they all automatically synchronize their route tables. If one vSmart controller fails, the remaining systems take over management of the control plane, simply and automatically, and all routers in the network continue to receive current, consistent routing and TLOC updates from the remaining vSmart controllers.

Let's look at the redundancy provided by each of the Cisco SD-WAN hardware devices in support of network high availability.

Recovering from a Failure in the Control Plane

The combination of hardware component redundancy with the architecture of the Cisco SD-WAN control plane results in a highly available network, one that continues to operate normally and without interruption when a failure occurs in one of the redundant control plane components. Recovery from the total failure of a vSmart controller, vBond orchestrator, or router in the Cisco SD-WAN overlay network happens in basically the same way as the recovery from the failure of a regular router or server on the network: A preconfigured backup component is able to perform all necessary functions by itself.

In the Cisco SD-WAN solution, when a network device fails and a redundant device is present, network operation continues without interruption. This is true for all Cisco devices—vBond orchestrators, vSmart controllers, and routers. No user configuration is required to implement this behavior; it happens automatically. The OMP peering sessions running between Cisco devices ensure that all the devices have a current and accurate view of the network topology.

Let's examine failure recovery device by device.

Data Plane Software Support for High Availability

For data plane resiliency, the Cisco SD-WAN software implements the standard BFD protocol, which runs automatically on the secure IPsec connections between routers. These IPsec connections are used for the data plane, and for data traffic, and are independent of the DTLS tunnels used by the control plane. BFD is used to detect connection failures between the routers. It measures data loss and latency on the data tunnel to determine the status of the devices at either end of the connection.

BFD is enabled, by default, on connections between Cisco IOS XE SD-WAN devices and Cisco vEdge devices. BFD sends Hello packets periodically (by default, every 1 second) to determine whether the session is still operational. If a certain number of the Hello packets are not received, BFD considers that the link has failed and brings the BFD session down (the default dead time is 3 seconds). When BFD sessions goes down, any route that points to a next hop over that IPsec tunnel is removed from the forwarding table (FIB), but it is still present in the route table (RIB).

In the Cisco SD-WAN software, you can adjust the Hello packet and dead time intervals. If the timers on the two ends of a BFD link are different, BFD negotiates to use the lower value.

Using Affinity To Manage Network Scaling

In the Cisco SD-WAN overlay network, all Cisco IOS XE SD-WAN devices and Cisco vEdge devices establish control connections to all vSmart controllers, to ensure that the routers are always able to properly route data traffic across the network. As networks increase in size, with routers at thousands of sites and with 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 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 the vSmart controllers collocated in the same geographic region.

Establishing affinity between vSmart controllers and Cisco vEdge devices allow you to control the scaling of the overlay network, by limiting the number of vSmart controllers that a Cisco vEdge device can establish control connections (and form TLOCs) with. When you have redundant routers in a single data center, affinity allows you to distribute the vEdge control connections across the vSmart controllers. Similarly, when you have multiple data centers in the overlay network, affinity allows you to distribute the vEdge 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 vSmart controller or to a single data center fails.

A simple case for using affinity is when redundant vSmart controllers are collocated in a single data center. Together, these vSmart controllers service all the Cisco vEdge devices in the overlay network. The figure below illustrates this situation, showing a scenario with three vSmart controllers in the data center and, for simplicity, showing just three of the many Cisco vEdge devices in the network.

If you do not enable affinity, each Cisco vEdge device establishes a control connection—that is, a TLOC—to each of the three vSmart controllers in the data center. Thus, a total of nine TLOCs are established, and each router exchanges OMP updates with each controller. Having this many TLOCs can strain the resources of both the vSmart controllers and the Cisco vEdge devices , and the strain increases in networks with larger numbers of Cisco vEdge devices .

Enabling affinity allows each Cisco vEdge device to establish TLOC connections with only a subset of the vSmart controllers. The figure above shows each router connecting to just two of the three vSmart controllers, thus reducing the total number of TLOCs from nine to six. Both TLOC connections can be active, for a total of six control connections. It is also possible for one of the TLOC connections be the primary, or preferred, and the other to be a backup, to be used as an alternate only when the primary is unavailable, thus reducing the number of active TLOCs to three.

Affinity also enables redundancy among data centers, for a scenario in which multiple vSmart controllers are collocated in two or more data centers. Then, if the link between a Cisco vEdge device and one of the data centers goes down, the vSmart controllers in the second data center are available to continue servicing the overlay network. The figure below illustrates this scenario, showing three vSmart controllers in each of two data centers. Each of the three Cisco vEdge devices establishes a TLOC connection to one controller in the West data center and one in the East data center.

You might think of the scenario in the figure above as one where there are redundant data centers in the same region of the world, such as in the same city, province, or country. For an overlay network that spans a larger geography, such as across a continent or across multiple continents, you can use affinity to limit the network scale either by restricting Cisco vEdge devices so that they connect only to local vSmart controllers or by having Cisco vEdge devices preferentially establish control connections with data centers that are in their geographic region. With geographic affinity, Cisco vEdge devices establish their only or their primary TLOC connection or connections with vSmart controllers in more local data centers, but they have a backup available to a more distant region to provide redundancy in case the closer data centers become unavailable. The figure below illustrates this scenario, Here, the Cisco vEdge devices in Europe have their primary TLOC connections to the two European data centers and alternate connections to the data centers in North America. Similarly, for the Cisco vEdge devices in North America, the primary connections are to the two North American data centers, and the backup connections are to the two European data centers.

As is the case with any overlay network that has multiple vSmart controllers, all policy configurations on all the vSmart controllers must be the same.

Before you cofigure High availability, to start with the configuration transaction, you can use the following command such as, 

ntp server 198.51.241.229 source GigabitEthernet1 version 4

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.

Cisco vManage Server Redundancy

The Cisco vManage servers comprise a centralized network management system that enables configuration and management of the Cisco devices in the overlay network. It also provides a real-time dashboard into the status of the network and network devices. The Cisco vManage servers maintain permanent communication channels with all Cisco vEdge devices in the network. Over these channels, the Cisco vManage servers push out files that list the serial numbers of all valid devices, they push out the configuration of each device, and they push out new software images as part of a software upgrade process. From each network device, the Cisco vManage servers receive various status information that is displayed on the Cisco vManage Monitor > Overview page.

Note

In Cisco vManage Release 20.6.x and earlier releases, the status information is available on the Dashboard > Main Dashboard page.

A highly available Cisco SD-WAN network contains three or more Cisco vManage servers in each domain. This scenario is referred to as a cluster of Cisco vManage servers, and each Cisco vManage server in a cluster is referred to as a Cisco vManage instance. Each Cisco vManage instance in a cluster can manage approximately 2000 devices, so a cluster of three Cisco vManage instances can manage up to 6000 devices. The Cisco vManage instances automatically load balances the devices that they manage. With three instances, the Cisco vManage cluster remains operational if one of the devices in that cluster fail.

For related information, see Troubleshooting TechNotes.

A Cisco vManage cluster consists of the following architectural components:

  • Application server—This provides a web server for user sessions. Through these sessions, a logged-in user can view a high-level dashboard summary of networks events and status, and can drill down to view details of these events. A user can also manage network serial number files, certificates, software upgrades, device reboots, and configuration of the Cisco vManage cluster itself from the Cisco vManage application server.

  • Configuration database—Stores the inventory and state and the configurations for all Cisco vEdge devices.

  • Network configuration system—Stores all configuration information, policies, templates, certificates, and more.

  • Statistics database—Stores the statistics information collected from all Cisco devices in the overlay network.

  • Message bus—Communication bus among the different Cisco vManage instances. This bus is used to share data and coordinate operations among the Cisco vManage instances in the cluster.

The Statistics database and Configuration database services must run on an odd number of Cisco vManage instances, with a minimum of three. For these databases to be writeable, there must be a quorum of Cisco vManage instances running and they should be in sync. A quorum is a simple majority. For example, if you have a cluster of three Cisco vManage instances running these databases, then two must be running and in sync. Initially, all Cisco vManage instances run the same services. However, you can choose not to run some services on some instances. From the Cluster Management window, you can select the services that can run on each Cisco vManage instance. You can add a fourth Cisco vManage instance to load balance more Cisco vEdge device s. In such a case, disable the statistics database and configuration database on one of the instances Cisco vManage because those services need to run on an odd number of instances. Optionally, you can run the configuration database on a single instance to reduce the amount of information shared between the devices and reduce load.

The following figure shows the interaction between Cisco vManage instances in a cluster, although a minimum of three devices are required. The figure illustrates the Cisco vManage services that synchronize between the Cisco vManage instances. Also in this figure, you see that each Cisco vManage instance resides on a virtual machine (VM). The VM can have from one to eight cores, with a Cisco SD-WAN software process (vdaemon) running on each core. In addition, the VM stores the actual configuration for the Cisco vManage server itself.

The Cisco vManage cluster implements an active-active architecture in the following way:

  • Each of the Cisco vManage instance in the cluster is an independent processing node.

  • All Cisco vManage instances are active simultaneously.

  • All user sessions to the application server are load balanced by using an external load balancer.

  • All control sessions between the Cisco vManage application servers and the routers are load balanced. A single Cisco vManage instance can manage a maximum of about 2000 Cisco vEdge devices . However, all the controller sessions—the sessions between the Cisco vManage instances and the Cisco vSmart Controllers, the sessions between the Cisco vManage instances and the Cisco vBond Orchestrators are arranged in a full-mesh topology.

  • The configuration and statistics databases can be replicated across Cisco vManage instances, and these databases can be accessed and used by all the Cisco vManage instances.

  • If one of the Cisco vManage instances in the cluster fails or otherwise becomes unavailable, the network management services that are provided by the Cisco vManage server are still fully available across the network.

The message bus among the Cisco vManage instances in the cluster allows all the instances to communicate using an out-of-band network. This design, which leverages a third vNIC on the Cisco vManage VM, avoids using WAN bandwidth for management traffic.

You configure the Cisco vManage cluster from the Cisco vManage web application server. During the configuration process, you can configure each Cisco vManage instance that can run the following services:

  • Application server—Each Cisco vManage server runs an application server instance.

  • Configuration database—Within the Cisco vManage cluster, no more than three iterations of the configuration database can run.

  • Load balancer—The Cisco vManage cluster requires a load balancer to distribute user login sessions among the Cisco vManage instances in the cluster. As mentioned, a single Cisco vManage instance can manage a maximum of about 2000 WAN edge devices.

  • Messaging server—We recommend that you configure each Cisco vManage instance to run the message bus so that all the instances in the cluster can communicate with each other.

  • Statistics database—Within a Cisco vManage cluster, no more than three iterations of the statistics database can run.

  • Coordination server: It’s used internally by the Messaging server.

The following are the design considerations for a Cisco vManage cluster:

  • A Cisco vManage cluster should consist of a minimum of three Cisco vManage instances.

  • The application server and message bus should run on all Cisco vManage instances.

  • Within a cluster, a maximum of three instances of the configuration database and three instances of the statistics database can run. However, any individual Cisco vManage instance can run both, one, or none of these two databases.

  • To provide the greatest availability, we recommend that you run the configuration and statistics databases on three Cisco vManage instances.

Deploy Cisco vManage Cluster


Note

Prerequisites for Cisco SD-WAN Releases 20.3.1, 20.3.2, 20.3.2.1, and 20.4.1 Only

Starting with Cisco SD-WAN Release 20.3.1, you must run the messaging server on all the active instances of the Cisco vManage cluster, and form a full-mesh messaging cluster.

When upgrading to Cisco SD-WAN Releases 20.3.1 and later from earlier releases, ensure that you run the messaging server on each of the Cisco vManage instance, prior to the upgrade.

Ensure that you have a minimum of three Cisco vManage instances in a Cisco vManage cluster.

The deployment process requires multiple reboots and should be performed during a scheduled maintenance window.

  1. Back up the Cisco vManage database. Use the following command to back up.

    request nms configuration-db backup path /home/admin/<db _ backup _ filename>

  2. If the current device has only two network interface cards (NICs), add a third NIC, don’t use Dynamic Host Configuration Protocol (DHCP) for addressing. This third NIC is used for cluster messaging between the devices ofCisco vManage instances, within vpn 0. For a device to detect the new interface, the device must be rebooted. Configure the interface and verify that it has connectivity.

  3. From the Cisco vManage menu, choose Administration > Cluster Management, edit the IP address to change localhost to the IP address of the third NIC, which is used for cluster messaging.

  4. Restart the Cisco vManage services. This may take some time. You can view the /var/log/nms/vmanage-server.log for the log output to stabilize, and then use the request nms all status command to determine for how long the processes have been running. When it comes up, verify that Cisco vManage is operational and stable.

  5. Provision two more Cisco vManage VMs in your virtual environment with the appropriate disk size and third NIC.

  6. Configure two more Cisco vManage VMs with minimal system configuration and addressing for the NICs. Configure the admin user password to match that is configured on the original device. If you’re using enterprise certificates, ensure that you install the root certificate chain on the new device as you did with the first device. Also, ensure that the clocks of the new devices are in sync with the original device.

    The following is a sample of a minimal configuration:

    system 
            host-name             vManage3 
            system-ip             10.0.1.102 
            site-id               1 
            organization-name     cisco-sdwan1 
            vbond vbond!    
            vpn 0  
                host vbond ip 198.51.100.103 192.51.100.104     
                interface eth0  
                ip address 198.51.100.102/24      
                tunnel-interface  
                no shutdown 
                ! 
                interface eth1  
                ip address 198.51.100.102/24  
                no shutdown ! 
                ip route 0.0.0.0/0 0.0.0.0     
                !
                vpn 512 
                interface eth2  
                    ip address 198.56.101.102/24  
                    no shutdown 
                !

    Note

    While a default gateway is given for the out of band Cisco vManage cluster interfaces, it’s not required if the Cisco vManage cluster nodes are using addresses in the same subnet and are adjacent.

  7. From the Cisco vManage menu, choose Administration > Cluster Management, to add one of the new Cisco vManage VMs to the cluster by adding the IP address of the third NIC for database replication, click Add vManage. Choose all services.

    The processes for the second Cisco vManageinstance restarts. This process might take some time. View the /var/log/nms/vmanage-server.log and then use the request nms all status command to determine process completion time.

  8. View the new device on the second Cisco vManage instances, by clicking Configuration > Certificates > Controllers.

  9. Generate a certificate signing request (CSR), get the device signed, and install the signed device certificate for this new device. For more information, see Cluster Management.

    The cluster shows that the new device on the second instance of Cisco vManage is rebalancing and that the Cisco vManage services are restarting on the device on previous Cisco vManage instance. A new task appears in the task bar for the Cluster Sync. Although the task appears as Complete, view the /var/log/nms/vmanage-server.log to resolve errors, if any.

    The first instance of Cisco vManage also restarts services, which eventually reset the GUI session. It might take several minutes for the GUI to become available after the services restarts. View the /var/log/nms/vmanage-server.log, and then use the request nms all status command.

  10. Wait for Cluster Sync to complete. View the vmanage-server.log to resolve errors, if any.

  11. After the Cluster Sync is completed, add the second of the new Cisco vManage VMs to the cluster by adding the IP address of the third NIC for database replication. Select all services.

    The third instance of Cisco vManage restarts services. This might take some time. A new task appears in the task bar for the Cluster Sync. The first and second instances of Cisco vManage also restart services, which eventually reset the GUI session. It may take several minutes for the GUI to become available after the Cisco vManage services restart. The device on the new Cisco vManage instance appears on the Configuration > Certificates > Controllers page. Perform steps 9 and 10 for this device.

Upgrade vManage Cluster

To upgrade a cluster, ensure that the services start in an orderly manner. After the upgrade steps, use the steps in the Restarting the NMS Processes section to start all the services in an orderly manner.

To get the software partitions prepared to be activated, upgrade the devices (without activating).

  1. Take backup of the Cisco vManage server. This can take a while. If Cisco hosts the controllers and there’s a recent snapshot, this step can be skipped. 

    request nms configuration-db backup path/home/admin/<db _ backup _ filename>

  2. Stop Cisco vManage services on all devices in the cluster by using the following command on each device. 

    request nms all stop

  3. Activate the new version on each device. This activation causes each device to reload.

    request software activate <version>

  4. If you do the upgrade from CLI, ensure that you manually confirm the upgrade from the CLI after the reload and before it reverts to the previous version. 

    request software upgrade-confirm

  5. After the devices reboot, stop Cisco vManage services on all devices in the cluster. 

    request nms all stop

Next, ensure that you perform the steps of restarting the Cisco vManage server manually.

Restarting the Cisco vManage Server Manually

When the cluster is in a bad state as part of the upgrade, you should manually restart the Cisco vManage server. To start the Cisco vManage server, restart the processes one at a time in an orderly manner instead of using request nms all restart or a similar command. The following manual restart order might vary for your cluster, depending on what services you’re running on the devices in the cluster. The following order is based on a basic cluster with three Cisco vManage instances.


Note

Consider bringing up the services manually as mentioned in the following method whenever you have to reboot a Cisco vManage server or after an upgrade.

  1. On each device, stop all Cisco vManage services. 

    request nms all stop

  2. Verify that all services have stopped. It’s normal for the preceding command to give some message about failing to stop a service if it takes too long, so use the following command to verify that everything is stopped before proceeding. 

    request nms all status

  3. Start the Statistics database on each device that is configured to run it. Wait for the service to start each time before proceeding to the next device. 

    request nms statistics-db start

  4. Verify that the service is started before proceeding to start it on the next device. After service starts, perform step 3 to start the Statistics database on the next device. Once all the devices, ensure that the Statistics database is running, and then proceed to the next step. 

    request nms statistics-db status

  5. Start the Configuration database on each device that is configured to run it. Wait for the service to start each time before proceeding to the next device. 

    request nms configuration-db start
  6. Verify that the service has started before proceeding to start it on the next device. Go to vshell and tail a log file to look for a database is online message. When confirmed, go to step 5 to start the Configuration database on the next device. After all devices have the Configuration database running, proceed to the next step.
    tail -f -n 100 /var/log/nms/debug.log

    Note
    For versions prior to 18.2, use this log file 
    tail -f -n 100 /var/log/nms/vmanage-orientdb-database.log

  7. Start the Coordination server on each device. Wait for the service to start each time before proceeding to the next device.

    request nms coordination-server start

  8. Verify that the service is started before proceeding to start it on the next device. After verifying, go to step 7 to start the Coordination server on the next device. After the Coordination server runs on all the devices, proceed to the next step. 

    request nms coordination-server status

  9. Start the Messaging server on each device. Wait for the service to start each time before proceeding to the next device.

    request nms messaging-server start

  10. Verify that the service has started before proceeding to start it on the next device. After verifying, go to step 9 to start the Messaging server on the next device. After the Messaging server runs on all devices, proceed to the next step. 

    request nms messaging-server status

  11. Start the Application server on each device. Wait for the service to start each time before proceeding to the next device.

    request nms application-server start

  12. Verify that the service has started before proceeding to start it on the next device. To verify if the service is fully started, open the GUI of that device. After the GUI is fully loaded and you’re able to log in, go to step 11 to start the Application server on the next device.

  13. Restart the Cisco vManage server cloud services on each device. Wait for the service to start each time before proceeding to the next device. 

     request nms cloud-agent start

  14. Verify that the service has started before proceeding to start it on the next device. After verifying, go to step 12 to start the cloud services on the next device. After the cloud services run on all devices, proceed to the next step. 

    request nms cloud-agent status

  15. To verify that there are no errors and everything has loaded cleanly, tail the log files.

Check Cisco vManage to verify that all devices appear as online and reachable, and that the statistics exist.

Cisco vManage Backups

Cisco manages Cisco vManage by taking regular snapshots of the devices for recovery due to a catastrophic failure or corruption. The frequency and retention of these snapshots are set for each overlay. Generally, the snapshots are taken daily and retained for up to 10 days. For certain scheduled maintenance activities, such as the upgrade of the devices, another snapshot can be taken before the scheduled activity. In all other cases, it’s your responsibility to take regular backups of the Cisco vManage configuration database and snapshots of the Cisco vManage virtual machine, and follow the example of frequency and retention that is followed by Cisco.

Cisco vManage Database Backup

Although the Cisco vManage cluster provides high availability and a level of fault tolerance, regular backup of the configuration database should be taken and stored securely off-site. Cisco vManage doesn’t have a mechanism of automating the collection of a configuration database backup on a schedule and copying it to another server. The greater the time between the backup and when it’s needed for a recovery, the greater the risk that data might be lost. Perform configuration database backups often. Use the following command to create a configuration database backup file.

request nms configuration-db backup path <path>

vSmart Controller Redundancy

vSmart Controller Redundancy

The vSmart controllers are the central orchestrators of the control plane. They have permanent communication channels with all the Cisco devices in the network. Over the DTLS connections between the vSmart controllers and vBond orchestrators and between pairs of vSmart controllers, the devices regularly exchange their views of the network, to ensure that their route tables remain synchronized. The vSmart controllers pass accurate and timely route information over DTLS connections to Cisco vEdge device .

A highly available Cisco SD-WAN network contains two or more vSmart controllers in each domain. A Cisco SD-WAN domain can have up to 20 vSmart controllers, and each router, by default, connects to two of them. When the number of vSmart controllers in a domain is greater than the maximum number of controllers that a domain's routers are allowed to connect to, the Cisco SD-WAN software load-balances the connections among the available vSmart controllers.

While the configurations on all the vSmart controllers must be functionally similar, the control policies must be identical. This is required to ensure that, at any time, all Cisco vEdge devices receive consistent views of the network. If the control policies are not absolutely identical, different vSmart controllers might give different information to a Cisco vEdge device , and the likely result will be network connectivity issues.


Note

To reiterate, the Cisco SD-WAN overlay network works properly only when the control policies on all vSmart controllers are identical. Even the slightest difference in the policies will result in issues with the functioning of the network.

To remain synchronized with each other, the vSmart controllers establish a full mesh of DTLS control connections, as well as a full mesh of OMP sessions, between themselves. Over the OMP sessions, the vSmart controllers advertise routes, TLOCs, services, policies, and encryption keys. It is this exchange of information that allows the vSmart controllers to remain synchronized.

You can place vSmart controllers anywhere in the network. For availability, it is highly recommended that the vSmart controllers be geographically dispersed.

Each vSmart controller establishes a permanent DTLS connection to each of the vBond orchestrators. These connections allow the vBond orchestrators to track which vSmart controllers are present and operational. So, if one of the vSmart controller fails, the vBond orchestrator does not provide the address of the unavailable vSmart controller to a router that is just joining the network.

To reiterate, the Cisco SD-WAN overlay network works properly only when the control policies on all vSmart controllers are identical. Even the slightest difference in the policies result in issues with the functioning of the network.

Recovering from a vSmart Controller Failure

The vSmart controllers are the primary controllers of the network. To maintain this control, they maintain permanent DTLS connections to all the vBond orchestrators and Cisco IOS XE SD-WAN devices and Cisco vEdge devices. These connections allow the vSmart controllers to be constantly aware of any changes in the network topology. When a network has multiple vSmart controllers:

  • There is a full mesh of OMP sessions among the vSmart controllers.

  • Each vSmart controller has a permanent DTLS connection to each vBond orchestrator.

  • The vSmart controllers have permanent DTLS connections to the Cisco IOS XE SD-WAN devices and Cisco vEdge devices. More specifically, each router has a DTLS connection to one of the vSmart controllers.

If one of the vSmart controllers fails, the other vSmart controllers seamlessly take over handling control of the network. The remaining vSmart controllers are able to work with Cisco IOS XE SD-WAN devices and Cisco vEdge devices joining the network and are able to continue sending route updates to the routers. As long as one vSmart controller is present and operating in the domain, the Cisco SD-WAN network can continue operating without interruption.

For more information about configuring graceful restart for OMP, see graceful restart.

Cisco vEdge Device Redundancy

The Cisco vEdge device are commonly used in two ways in the Cisco SD-WAN network: to be the Cisco SD-WAN routers at a branch site, and to create a hub site that branch routers connect to.

A branch site can have two Cisco vEdge device s in a branch site for redundancy. Each of the router maintains:

  • A secure control plane connection, via a DTLS connection, with each vSmart controller in its domain

  • A secure data plane connection with the other routers at the site

Because both the routers receive the same routing information from the vSmart controllers, each one is able to continue to route traffic if one fails, even if they are connected to different transport providers.

When using Cisco IOS XE SD-WAN devices and Cisco vEdge devices in a hub site, you can provide redundancy by installing two Cisco vEdge device s. The branch routers need to connect to each of the hub routers by using separate DTLS connections.

You can also have Cisco vEdge device provide redundancy by configuring up to tunnel interfaces on a single router. Each tunnel interface can go through the same or different firewalls, service providers, and network clouds, and each maintains a secure control plane connection, by means of a DTLS tunnel, with the vSmart controllers in its domain.

Recovering from a Cisco vEdge Device Failure

The route tables on Cisco IOS XE SD-WAN devices and Cisco vEdge devices are populated by OMP routes received from the vSmart controllers. For a site or branch with redundant routers, the route tables on both routers remain synchronized, so if either of the routers fail, the other one continues to be able to route data traffic to its destination.

Configure Affinity Between vSmart Controllers and Cisco vEdge Device

One way to manage network scale is to configure affinity between vSmart controllers and Cisco vEdge device s. To do this, you place each vSmart controller into a controller group, and then you configure which group or groups a Cisco vEdge device can establish control connections with. The controller groups are what establishes the affinity between vSmart controllers and Cisco vEdge device .

Configure Controller Group Identifier on vSmart Controllers

To participate in affinity, each vSmart controller must be assigned a controller group identifier:

vSmart(config)#system controller-group-id number

The identifier number can be from 0 through 100.

When vSmart controllers are in different data centers, it is recommended that you assign different controller group identifiers to the vSmart controllers. Doing this provides redundancy among data centers, in case a data center becomes unreachable.

For vSmart controllers in the same a data center, they can have the same controller group identifier or different identifiers:

  • If the vSmart controllers have the same controller group identifier, a Cisco vEdge device establishes a control connection to any one of them. If that vSmart controller becomes unreachable, the router simply establishes a control connection with another one of the controllers in the data center. As an example of how this might work, if one vSmart controller becomes unavailable during a software upgrade, the Cisco vEdge device immediately establishes a new TLOC with another vSmart controller, and the router's network operation is not interrupted. This network design provides redundancy among vSmart controllers in a data center.

  • If the vSmart controllers have different controller group identifiers, a Cisco vEdge device can use one controller as the preferred and the other as backup. As an example of how this might work, if you are upgrading the vSmart controller software, you can upgrade one controller group at a time. If a problem occurs with the upgrade, a Cisco vEdge device establishes TLOCs with the vSmart controllers in the second, backup controller group, and the router's network operation is not interrupted. When the vSmart controller in the first group again becomes available, the Cisco vEdge device switches its TLOCs back to that controller. This network design, while offerring redundancy among the vSmart controllers in a data center, also provides additional fault isolation.

Configure Affinity on Cisco vEdge Device

For a Cisco vEdge device to participate in affinity, you configure the vSmart controllers that the router is allowed to establish control connections with, and you configure the maximum number of control connections (or TLOCs) that the Cisco vEdge device itself, and that an individual tunnel on the router, is allowed to establish.

Configure vSmart Controller Groups

Configuring the vSmart controllers that the router is allowed to establish control connections is a two-part process:

  • At the system level, configure a single list of all the controller group identifiers that are present in the overlay network.

  • For each tunnel interface in VPN 0 , you can choose to restrict which controller group identifiers the tunnel interface can establish control connections with. To do this, configure an exclusion list.

At a system level, configure the identifiers of the vSmart controller groups:

vEdge(config)#system controller-group-list numbers

List the vSmart controller group identifiers that any of the tunnel connections on the Cisco vEdge device might want to establish control connections with. It is recommended that this list contain the identifiers for all the vSmart controller groups in the overlay network.

If, for a specific tunnel interface in VPN 0 , you want it to establish control connections to only a subset of all the vSmart controller groups, configure the group identifiers to exclude: 

vEdge(config-vpn-0-interface)#tunnel-interface exclude-controller-group-list numbers

This command lists the identifiers of the vSmart controller groups that this particular tunnel interface should not establish control connections with. The controller groups in this list must be a subset of the controller groups configured with the system controller-group-list command.

If a Cisco vEdge device is not able to establish control connection with the configured controller group(s), the Cisco vEdge device will try to connect to the vSmart controllers from the excluded list.

To display the controller groups configured on a Cisco vEdge device, use the show control connections command.

Configure Maximum Number of Control Connections

Configuring the maximum number of control connections for the Cisco vEdge device is a two-part process:

  • At the system level, configure the maximum number of control connections that the Cisco vEdge device can establish to vSmart controllers.

  • For each tunnel interface in VPN 0 , configure the maximum number of control connections that the tunnel can establish to vSmart controllers.

By default, a Cisco vEdge device can establish two OMP sessions for control connections to vSmart controllers. To modify the maximum number of OMP sessions: 

vEdge(config)#system max-omp-sessions number

The number of OMP sessions can be from 0 through 100.

A Cisco vEdge device establishes OMP sessions as follows:

  • Each DTLS and and each TLS control plane tunnel creates a separate OMP session.

  • It is the Cisco vEdge device as a whole, not the individual tunnel interfaces in VPN 0 , that establishes OMP sessions with vSmart controllers. When different tunnel interfaces on the router have affinity with the same vSmart controller group, the Cisco vEdge device creates a single OMP session to one of the vSmart controllers in that group, and the different tunnel interfaces use this single OMP session.

By default, each tunnel interface in VPN 0 can establish two control connections. To change this:

vEdge(config-vpn-0-interface)#vpn 0 interface interface-name tunnel-interface max-control-connections number

The number of control connections can be from 0 through 100. The default value is the maximum number of OMP sessions configured with the system max-omp-sessions command.

When a Cisco vEdge device s has multiple WAN transport connections, and hence has multiple tunnel interfaces in VPN 0 , the sum of the maximum number of control connections that all the tunnels can establish cannot exceed the maximum number allowed on the router itself.

To display the maximum number of control connections configured on an interface, use the show control local-properties command.

To display the actual number of control connections for each tunnel interface, use the show control affinity config command.

To display a list of the vSmart controllers that each tunnel interface has established control connections with, use the show control affinity status command.

Configure Affinity for vSmart Controllers on Single Data Center

In an overlay network with a single data center that has multiple vSmart controllers, if you want the Cisco vEdge device to establish a single control connection to one of vSmart controllers, there is no need to configure affinity because this situation is the default behavior.

However, if you want the Cisco vEdge device to establish control connections to more than one vSmart controllers, to provide redundancy in case one of the controllers becomes unavailable, you configure affinity. You generally place the vSmart controllers in the same controller group.

Let's say that all the vSmart controllers use the same controller group identifier, 1. You configure the identifier on all three controllers as follows: 

vSmart(config)# system controller-group-id 1

To verify the configuration, use the show running-config command: 

vSmart# show running-config system
system
 description         "vSmart in data center 1"
 host-name           vSmart
 gps-location latitude 37.368140
 gps-location longitude -121.913658
 system-ip           172.16.255.19
 site-id             100
 controller-group-id 1
 organization-name   "Cisco"
 clock timezone America/Los_Angeles

We want the three Cisco vEdge device s to establish two control connections to two of the three vSmart controllers. We do this for purposes of redundancy, in case one of the controllers becomes available. Because all the vSmart controllers are in the same controller group, we cannot specify or influence which of the two controllers the Cisco vEdge device s connect to. The configurations on all three routers are effectively identical. We show here the configuration for router vEdge -1.

First, configure the available vSmart controller groups. This scenario has just one group:

vEdge-1(config)# system controller-group-list 1

By default, a Cisco vEdge device can establish two control connections. Because we want each Cisco vEdge device and each tunnel interface to connect to two vSmart controllers, no configuration is required here. However, if you want to explicitly configure these parameters, you configure the maximum number of OMP sessions at the system level and the maximum number of control connections per tunnel: 

vEdge-1(config)# system max-omp-sessions 2
vEdge-1(config)# vpn 0 interface ge0/2 tunnel-interface
vEdge-1(config-tunnel-interface)# max-control-connections 2

Here are the relevant configuration snippets from Cisco vEdge device-1: 

vEdge-1# show running-config system
system
 host-name             vEdge-1
 gps-location latitude 43.0
 gps-location longitude -75.0
 system-ip             172.16.255.11
 site-id               100
 max-omp-sessions      2
 controller-group-list 1
 organization-name     "Cisco"
 ...
vEdge-1# show running-config vpn 0
...
 interface ge0/2
  ip address 10.0.5.11/24
  tunnel-interface
   encapsulation ipsec
   color lte
   max-control-connections 1
   no allow-service bgp
   allow-service dhcp
   allow-service dns
   allow-service icmp
   no allow-service sshd
   no allow-service netconf
   no allow-service ntp
   no allow-service ospf
   no allow-service stun
  !
  no shutdown
...

To display the control connections with the vSmart controllers, use the show control connections command. The last column, Controller Group ID, lists the vSmart controller group that a router is in. 

vEdge-1# show control connections

                                                                            PEER         PEER                                      CONTROLLER
PEER     PEER     PEER             SITE    DOMAIN   PEER           PRIVATE  PEER         PUBLIC                                    GROUP     
TYPE     PROTOCOL SYSTEM IP        ID      ID       PRIVATE IP     PORT     PUBLIC IP    PORT    LOCAL COLOR   STATE    UPTIME     ID        
----------------------------------------------------------------------------------------------------------------------------------------------
vsmart   dtls     172.16.255.19    100     1        10.0.5.19      12446    10.0.5.19    12446   lte           up       0:00:00:53 1          
vsmart   dtls     172.16.255.20    200     1        10.0.12.20     12446    10.0.12.20   12446   lte           up       0:00:00:22 1

To display the maximum number of control connections allowed on the router, use the show control local-properties command. The last line of the output lists the maximum controllers. The following is the abbreviated output for this command: 

vEdge-1# show control local-properties

personality                  vedge
organization-name            Cisco
certificate-status           Installed
root-ca-chain-status         Installed

certificate-validity         Valid
certificate-not-valid-before Mar 10 19:50:04 2016 GMT
certificate-not-valid-after  Mar 10 19:50:04 2017 GMT
...

                         PUBLIC          PUBLIC PRIVATE         PRIVATE                                 PRIVATE                              MAX   RESTRICT/           LAST         SPI 
TIME    NAT  VM
INTERFACE                IPv4            PORT   IPv4            IPv6                                    PORT    VS/VM COLOR            STATE CNTRL CONTROL/     LR/LB  CONNECTION       
REMAINING   TYPE CON
                                                                                                                                                   STUN                                 
              PRF
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------------------
ge0/0                    2.1.1.11        12346  2.1.1.11        ::                                      12346    2/1  default          up     2      no/yes/no   No/No  2:19:35:21   
0:07:58:46  N    5

Two commands display information about the control connections established by the affinity configuration. To see, for each interface, which controller groups are configured and which the interface is connected to, use the show control affinity config command: 

vEdge-1# show control affinity config

EFFECTIVE CONTROLLER LIST FORMAT - G(C),...  - Where G is the Controller Group ID
                                                  C is the Required vSmart Count
CURRENT CONTROLLER LIST FORMAT - G(c)s,...   - Where G is the Controller Group ID
                                                  c is the current vSmart count
                                                  s Status ✓ when matches, χ when does not match
                 EFFECTIVE
                 REQUIRED
INDEX INTERFACE  VS COUNT   EFFECTIVE CONTROLLER LIST    CURRENT CONTROLLER LIST  EQUILIBRIUM 
---------------------------------------------------------------------------------------------
0     ge0/2      2           1(2)                        1(2)✓                    Yes

The command output above shows that affinity is configured on interface ge0/2.

  • The Effective Required and Count column shows that the interface is configured to create two control connections, and, in fact, two control connections have been established. You configure the number of control connections for the tunnel interface with the max-control-connections command.

  • The Effective Controller List column shows that affinity on the interface is configured to use Cisco vSmart Controller identifier 1 and that the router supports two OMP sessions. You configure the affinity controller identifiers with the controller-group-list command (at the system level) and, for the tunnel interface, the exclude-controller-group-list command.

  • The Current Controller List column lists the actual affinity configuration for the interface. The output here shows that the interface has two control connections with Cisco vSmart Controllers in group 1. The check mark indicates that the current and effective controller lists match each other. If, for example, the tunnel had established only one TLOC connection to a vSmart controller, this column would show "1(1)X".

  • The Equilibrium column indicates that the current controller lists matches what is expected from the affinity configuration for that tunnel interface.

To determine the exact Cisco vSmart Controllers that the tunnel interface has established control connections with, use the show control affinity status command: 

vEdge-1# show control affinity status

ASSIGNED CONNECTED CONTROLLERS - System IP( G),..       - System IP of the assigned vSmart
                                                             G is the group ID to which the vSmart belongs to

UNASSIGNED CONNECTED CONTROLLERS - System IP( G),..     - System IP of the unassigned vSmart
                                                             G is the group ID to which the vSmart belongs to

INDEX INTERFACE ASSIGNED CONNECTED  CONTROLLERS        UNASSIGNED CONNECTED CONTROLLERS
---------------------------------------------------------------------------------------------------------------
0     ge0/2     172.16.255.19(  1), 172.16.255.20(  1)

The command output above shows that interface ge0/2 has control connections to two vSmart controllers, 172.16.255.19 and 172.16.255.20, that both controllers are in group 1, and that both controllers are in one of the groups configured in the controller group list. If the interface were connected to a vSmart controller not in the controller group list, it would be listed in the Unassigned Connected Controllers column.

When a data center has multiple vSmart controllers, you can configure them to be in different controller groups. For example, if you configure them to be in two different controller groups, each Cisco vEdge device can establish two control connections, one to each of the groups. While this configuration design is similar to what we discussed in the previous section, providing redundant control connections to the vSmart controllers, on subtle difference is that it provides fault isolation between the two Cisco vSmart Controller groups in the data center. The configuration for this scenario is almost identical to the configuration when Cisco vSmart Controllers are two data centers. The only difference is that here, two Cisco vSmart Controller groups are collocated in the same data center. See the configuration example in the next section.

Configure Affinity for vSmart Controllers on Two Data Centers

You can use affinity to enable redundancy among data centers, for a network design in which multiple Cisco vSmart Controllers are spread across two or more data centers. Then, if the link between a Cisco vEdge device and one of the data centers goes down, the Cisco vSmart Controllers in the second data center are available to continue servicing the overlay network. The figure below illustrates this scenario, showing three Cisco vSmart Controllers in each of two data centers. Each of the three Cisco vEdge device s establishes a TLOC connection to one controller in the West data center and one in the East data center.

You configure the three vSmart controllers in DC1-West with controller group identifier 1:

vSmart-DC1(config)# system controller-group-id 1

The three vSmart controllers in DC2-East are in controller group 2:

vSmart-DC2(config)# system controller-group-id 2

We want all the Cisco vEdge device s to have a maximum of two OMP sessions, and we want each tunnel interface to have a maximum of two control connections and to not exclude any controller groups. So the only configuration that needs to be done on the routers is to set the controller group list. We want Cisco vEdge device s in the west to prefer Cisco vSmart Controllers in DC1-West over DC2-East: 

vEdge-West(config)# system controller-group-list 1 2

Similarly, we want Cisco vEdge device s in the east to prefer DC2-East: 

vEdge-East(config)# system controller-group-list 2 1

The software evaluates the controller group list in order, so with this configuration, the vEdge-West routers prefer vSmart controller group 1 (which is the West data center), and the vEdge-East routers prefer Cisco vSmart Controller group 2.

You can fine-tune the controller group preference in other ways:

  • Set the maximum number of OMP sessions allowed on the router to 1 (system max-omp-sessions 1). To illustrate how this works, let's look at a vEdge-West router. The router has only one tunnel interface, and that interface creates one control connection to Cisco vSmart Controller list 1. If all the Cisco vSmart Controllers in this group become unavailable, or if the connection between the router that the DC1-West data center goes down, the tunnel interface establishes one control connection to Cisco vSmart Controller list 2, because this group is listed in the system controller-group-list command. If all Cisco vSmart Controllers in both controller groups, or the connections to them, become unavailable, and if the vBond orchestrator also indicates that all these vSmart controllers are unreachable, the tunnel interface establishes a control connection to any other Cisco vSmart Controller in the overlay network if other controllers are present.

  • Set the maximum number of control connections that the tunnel interface can establish to 1 ( vpn 0 sdwan interface tunnel-interface max-control-connections 1 ). Because the software evaluates the controller group list in order, for a vEdge-West router, this configuration forces the tunnel interface to establish a control connection to Cisco vSmart Controller group 1. Again, if this controller group or data center becomes unreachable, the tunnel establishes a control connection with controller group 2, because this group is configured in the system controller-group-list command. And if neither controller group 1 or 2 is available, and if another vSmart controller is present in the network, the tunnel interface establishes a control connection with that controller.

  • Exclude the non-preferred Cisco vSmart Controller group for a particular tunnel. For example, for a vEdge-West router to prefer controller group 1, you configure vpn 0 interface tunnel-interface exclude-controller-group-list 2 . As with the above configurations, if this controller group or data center becomes unreachable, the tunnel establishes a control connection with controller group 2, because this group is configured in the system controller-group-list command. And if neither controller group 1 or 2 is available, and if another Cisco vSmart Controller is present in the network, the tunnel interface establishes a control connection with that controller.

Configure Redundant Control Connections on Single Device

When a router has two tunnel connections and the network has two (or more) data centers, you can configure redundant control connections from the Cisco vEdge device to Cisco vSmart Controllers in two of the data centers. It is recommended that do this using the minimum number of OMP sessions—in this case, two. To do this, you configure one of the tunnel interfaces to go only to one of the data centers and the other to go only to the second. This configuration provides vSmart redundancy with the minimum number of OMP sessions.

On the Cisco vEdge device router, define the controller group list and configure the maximum number of OMP sessions to be 2: 

vEdge(config-system)# controller-group-list 1 2
vEdge(config-system)# max-omp-sessions 2

For one of the tunnels, you can use the default affinity configuration (that is, there is nothing to configure) to have this tunnel prefer a Cisco vSmart Controller in group 1. You can also explicitly force this tunnel to prefer Cisco vSmart Controller group 1: 

vEdge(config-tunnel-interface-1)# max-control-connections 1

You do not need to configure exclude-controller-group-list 2 , because the software evaluates the controller group list in order, starting with group 1. However, you could choose to explicitly exclude vSmart controller group 2.

Then, on the second tunnel, configure it to prefer a vSmart controller in group 2. As with the other tunnel, you limit the maximum number of control connections to 1. In addition, you have to exclude controller group 1 for this tunnel. 

vEdge(config-tunnel-interface-2)# max-control-connections 1
vEdge(config-tunnel-interface-2)# exclude-controller-group-list 1

Configure Control Plane and Data Plane High Availability Parameters

This topic discusses the configurable high availability parameters for the control plane and the data plane.

Control Plane High Availability

A highly available Cisco SD-WAN network contains two or more vSmart controllers in each domain. A Cisco SD-WAN domain can have up to 20 vSmart controllers, and each Cisco vEdge device , by default, connects to two of them. You change this value on a per-tunnel basis: 

vEdge(config-tunnel-interface)# max-control-connections number

Note

The no-control-connections command is not applicable. Instead, use the max-control-connections command.

When the number of vSmart controllers in a domain is greater than the maximum number of controllers that a domain's Cisco vEdge devices are allowed to connect to, the SD-WAN software load-balances the connections among the available vSmart controllers.


Note

To maximize the efficiency of the load-balancing among vSmart controllers, use sequential numbers when assigning system IP addresses to the Cisco vEdge devices in the domain. One example of a sequential numbering schemes is 172.1.1.1, 172.1.1.2, 172.1.1.3, and so forth. Another is 172.1.1.1, 172.1.2.1, 172.1.3.1, and so forth.

Data Plane High Availability

BFD, which detects link failures as part of the Cisco SD-WAN high availability solution, is enabled by default on all Cisco devices. BFD runs automatically on all IPsec data tunnels between Cisco vEdge devices. It does not run on the control plane (DTLS or TLS) tunnels that vSmart controllers establish with all Cisco devices in the network.

You can modify the BFD Hello packet interval and the number of missed Hello packets (the BFD interval multiplier) before BFD declares that a link has failed.

Change the BFD Hello Packet Interval

BFD sends Hello packets periodically to detect faults on the IPsec data tunnel between two Cisco vEdge devices. By default, BFD sends these packets every 1000 milliseconds (that is, once per second). To change this interval on one or more traffic flow, use the hello-interval command: 

vEdge(config)#bfd color color hello-interval milliseconds

The interval can be a value from 100 to 300000 milliseconds (5 minutes).

Configure the interval for each tunnel connection, which is identified by a color. The color can be 3g, biz-internet, blue, bronze, custom1, custom2, custom3, default, gold, green, lte, metro-ethernet, mpls, private1, private2, public-internet, red, or silver.

Change the BFD Packet Interval Multiplier

After BFD has not received a certain number of Hello packets on a link, it declares that the link has failed. This number of packets is a multiplier of the Hello packet interval time. By default, the multiplier is 7 for hardware routers and 20 for Cloud software routers. This means that if BFD has not received a Hello packet after 7 seconds, it considers that the link has failed and implements its redundancy plan.

To change the BFD packet interval multiplier, use the multiplier command: 

vEdge(config)#bfd color color multiplier integer

Multiplier range: 1 to 60 (integer)

You configure the multiplier for each tunnel connection, which is represented by a color.

Control PMTU Discovery

On each transport connection (that is, for each TLOC, or color), the Cisco SD-WAN BFD software performs path MTU (PMTU) discovery, which automatically negotiates the MTU size in an effort to minimize or eliminate packet fragmentation on the connection. BFD PMTU discovery is enabled by default, and it is recommended that you use BFD PMTU discovery and not disable it. To explicitly enable it: 

vEdge(config)#bfd color color pmtu-discovery

With PMTU discovery enabled, the path MTU for the tunnel connection is checked periodically, about once per minute, and it is updated dynamically. With PMTU discovery enabled, 16 bytes might be required by PMTU discovery, so the effective tunnel MTU might be as low as 1452 bytes. From an encapsulation point of view, the default IP MTU for GRE is 1468 bytes, and for IPsec it is 1442 bytes because of the larger overhead. Enabling PMTU discovery adds to the overhead of the BFD packets that are sent between the Cisco vEdge devices, but does not add any overhead to normal data traffic.

If PMTU discovery is disabled, the expected tunnel MTU is 1472 bytes (tunnel MTU of 1500 bytes less 4 bytes for the GRE header, 20 bytes for the outer IP header, and 4 bytes for the MPLS header). However, the effective tunnel MTU might be 1468 bytes, because the software might sometimes erroneously add 4 bytes to the header.

Configure High Availability

CLI commands for configuring and monitoring high availability.

High Availability Configuration Commands

Use the following commands to configure high availability on a Cisco vEdge device: 

bfd
  app-route
    multiplier number 
    poll-interval milliseconds 
  color color
    hello-interval milliseconds
    multiplier number
    pmtu-discovery

High Availability Monitoring Commands

show bfd sessions —Display information about the BFD sessions running on the local Cisco vEdge device.

Best Practices for Configuring Affinity

  • In the system controller-group-list command on the Cisco vEdge device , list all the controller groups available in the overlay network. Doing so ensures that all the vSmart controllers in the overlay network are available for the affinity configuration, and it provides additional redundancy in case connectivity to the preferred group or groups is lost. You manipulate the number of control connections and their priority based on the maximum number of OMP sessions for the router, the maximum number of control connections for the tunnel, the controller groups a tunnel should not use. A case in which listing all the controller groups in the system controller-group-list command provides additional redundancy is when the Cisco vEdge device site is having connectivity issues in reaching the vSmart controllers in the controller group list. To illustrate this, suppose, in a network with three controller groups (1, 2, and 3), the controller group list on a Cisco vEdge device contains only groups 1 and 2, because these are the preferred groups. If the router learns from the vBond controller that the vSmart controllers in groups 1 and 2 are up, but the router is having connectivity issues to both sites, the router loses its connectivity to the overlay network. However, if the controller group list contains all three controller groups, even though group 3 is not a preferred group, if the router is unable to connect to the vSmart controllers in group 1 or group 2, it is able to fall back and connect to the controllers in group 3. Configuring affinity and the order in which to connect to vSmart controllers is only a preference. The preference is honored whenever possible. However, the overarching rule in enforcing high availability on the overlay network is to use any operational vSmart controller. The network ceases to function only when no vSmart controllers are operational. So it might happen that the least preferred vSmart controller is used if it is the only controller operational in the network at a particular time. When a Cisco vEdge device boots, it learns about all the vSmart controllers in the overlay network, and the vBond orchestrator is continuously communicating to the router which vSmart controllers are up. So, if a Cisco vEdge device cannot reach any of the preferred vSmart controllers in the configured controller group and another vSmart controller is up, the router connects to that controller. Put another way, in a network with multiple vSmart controllers, as a last resort, a Cisco vEdge device connects to any of the controllers, to ensure that the overlay network remains operational, whether or not these controllers are configured in the router's controller group list.

  • The controller groups listed in the exclude-controller-group-list command must be a subset of the controller groups configured for the entire router, in the system controller-group-list command.

  • When a data center has multiple vSmart controllers that use the same controller group identifier, and when the overlay network has two or more data centers, it is recommended that the number of vSmart controllers in each of the controller groups be the same. For example, if Data Center 1 has three vSmart controllers, all with the same group identifier (let's say, 1), Data Center 2 should also have three vSmart controllers, all with the same group identifier (let's say, 2), and any additional data centers should also have three vSmart controllers.

  • When a data center has vSmart controllers in the same controller group, the hardware capabilities—specifically, the memory and CPU—on all the vSmart controllers should be identical. More broadly, all the vSmart controllers in the overlay network, whether in one data center or in many, should have the same hardware capabilities. Each vSmart controller should have equal capacity and capability to handle a control connection from any of the Cisco vEdge device s in the network.

  • When a router has two tunnel connections and the network has two (or more) data centers, it is recommended that you configure one of the tunnel interfaces to go to one of the data centers and the other to go to the second. This configuration provides vSmart redundancy with the minimum number of OMP sessions.

  • Whenever possible in your network design, you should leverage affinity configurations to create fault-isolation domains.

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