Modem with IPv6 in OpenWRT router

Good afternoon, tell me how to solve the following problem, there is a router with OpenWRT firmware, a modem with HiLink firmware is connected to it, in OpenWRT it works via cdc-ether via the dhcp protocol. If you connect the modem directly to the PC, then there is access to IPv6, everything works, but there is no router. In OpenWRT, I create two interfaces, wan with dhcp and wan6 with dhcpIPv6 issues two addresses /64 and / 128, it turns out to ping IPv6 addresses from the router, but devices connected to the router do not have access.