Keep pfSense DHCPv6 addressing separate from IPv6 gateway discovery

Receiving an IPv6 address does not mean DHCPv6 supplied the default gateway.

Source facts

Netgate explains that DHCPv6 configures items such as the interface address, prefix length, and DNS servers, but the gateway is learned through router advertisements. IPv4 and IPv6 default gateways operate independently. Provider-specific prefix delegation and client requirements must come from the ISP rather than a generic example copied from another circuit.

Source: Netgate — IPv6 Configuration Types.

Applicability

This concerns pfSense WAN IPv6 configuration.

DSE recommendation

DSE recommends obtaining the provider’s address, delegated-prefix, and router-advertisement requirements before selecting interface options. Diagnose address acquisition and default-route discovery as separate events. Record which internal interfaces track the delegated prefix and avoid selecting an upstream gateway on an ordinary internal LAN. Keep IPv6 acceptance criteria independent of IPv4 so an apparently successful dual-stack browser request does not conceal a broken protocol path. Collect address assignment and default-route evidence as separate acceptance items for the affected circuit. Ask the ISP to confirm the circuit’s delegation requirements in writing, and retain that answer with the interface design. A successful IPv4 test should not close an unresolved IPv6 router-advertisement or return-path finding.

Verification

Inspect the obtained address, delegated prefix, router advertisement, and active IPv6 default route. From an approved client, test DNS and an intended IPv6 service explicitly. Repeat after the WAN reconnects and confirm that internal prefix tracking and return routing still match the provider’s documented arrangement.

Official reference

Netgate — IPv6 Configuration Types. Reviewed October 20, 2026.