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SD-WAN

Network > SD-WAN manages several WAN links. It monitors each link, switches traffic away from one that fails, and can spread or steer traffic according to policy.

Concepts​

  • Gateway: a WAN interface taking part in SD-WAN.
  • Policy: how traffic is distributed over the gateways, for example "use link A, fall back to link B" or "balance between A and B".
  • Rule: assigns a policy to some traffic.

Policies​

Open the Policies tab. With more than one WAN, the default policy is mandatory and cannot be deleted. Create other policies for special cases, such as "video conferencing always over the fastest link". A policy lists its gateways with a weight or an order, depending on whether you want to balance or to have a primary and a backup.

Rules​

Rules choose which policy applies to which traffic. Match on source, destination, protocol and ports (you can use objects), then pick the policy. The default rule is at the end of the list, so place your rules above it. Rules are evaluated in order.

The sticky option keeps traffic from the same source on the same link as its previous session for a period (ten minutes by default). It avoids problems with services that are sensitive to the source address changing.

Tracking​

For each WAN, the unit pings a set of hosts to decide whether the link works. The link stays active while at least one host answers. Configure:

  • the hosts to ping (addresses or names). Choose hosts that are reliable and that you do not mind pinging;
  • how often to ping and how long to wait;
  • how many failed tests take a link down, and how many successful tests bring it back up.

The default values fit most connections. Change them only if links flap or take too long to recover.