I would like to be able to add ULA addresses (fc00::/7) to each VLAN interface. Normally, the router uses DHCPv6-PD with a prefix ID. However if the WAN is down, this could cause the router to lose its GUA addresses. ULA addresses are useful for out-of-band access to devices on the LAN, and also for internal services that require consistent addresses that do not change (for instance when the ISP changes the delegated prefix, or changing to a different ISP).
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