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SD-WAN policy routing behavior

You can use SD-WAN routes to route system-generated traffic and reply packets.

System-generated traffic and reply packets

You can create SD-WAN routes and specify the gateways for system-generated traffic and reply packets. On the CLI, make sure you turn on routing for both.

Reply packets

Sophos Firewall enforces symmetric routing on WAN interfaces for reply packets. These packets use the same WAN interface as the original packets.

You can configure asymmetric routing for reply packets on non-WAN interfaces. For example, you can specify an interface other than the original traffic's interface for LAN to DMZ traffic.

Restriction

SD-WAN routes don't apply to reply packets if the original traffic uses the default route (WAN link load balance). The default route applies, and reply packets exit on the same interface they enter.

You can change the setting on the CLI. See Routing commands.

System-generated traffic

Select only the destination networks and services because the incoming interface and source networks remain unknown. For example, traffic related to services used by Sophos Firewall flows through different interfaces, depending on the type of service.

You can change the setting on the CLI. See Routing commands.

Note

  • The firewall doesn't forward system-generated traffic if you select all the configured gateways as Backup on Network > WAN link manager. You must select at least one of them as Active.
  • System-generated RED traffic on UDP port 3410 is layer 2 traffic. So, SD-WAN routes don't apply to this traffic.

Route-based VPNs with SD-WAN routes

You can use SD-WAN routes with route-based IPsec VPN connections. You can select the XFRM interface's gateway in SD-WAN profiles or SD-WAN routes. See Create a route-based VPN (any to any subnets).

To compress the IPsec tunnel's traffic to increase the throughput, go to Profiles > IPsec profiles and select Pass data in compressed format for the profile you've selected in the route-based VPN configuration.