root@OpenWrt:~# cat /etc/config/network

config interface 'loopback'
	option ifname 'lo'
	option proto 'static'
	option ipaddr '127.0.0.1'
	option netmask '255.0.0.0'

config interface 'lan'
	option ifname 'eth0.1'
	option type 'bridge'
	option proto 'static'
	option netmask '255.255.255.0'
	option ipaddr '192.168.3.1'

config interface 'wan'
	option ifname 'eth1'
	option _orig_ifname 'eth1'
	option _orig_bridge 'false'
	option proto 'pppoe'
	option username '@t-online.de'
	option password ''
	option ipv6 '1'
	option accept_ra 1

config switch
	option name 'switch0'
	option reset '1'
	option enable_vlan '1'

config switch_vlan
	option device 'switch0'
	option vlan '1'
	option ports '0 1 2 3 5t'

root@OpenWrt:~# cat /etc/config/network6

config global 'global'
	option ula_prefix 'fd13:xxxx:xxxx::/48'

config interface 'wan'
	option mode 'dhcpv6'
	option request_prefix 'auto'
	option prefix_fallback 'relay'
	option peerdns '1'
	option site_border '1'

config interface 'lan'
	option mode 'router'
	option advertise_prefix '64'
	option relay_master 'wan'

root@OpenWrt:~# cat /etc/config/radvd
config interface
	option interface	'lan'
	option AdvSendAdvert	1
	option AdvManagedFlag	0
	option AdvOtherConfigFlag 0
	list client		''
	option ignore		0

config prefix
	option interface	'lan'
	# If not specified, a non-link-local prefix of the interface is used
	list prefix		''
	option AdvOnLink	1
	option AdvAutonomous	1
	option AdvRouterAddr	0
	option ignore		0

config route
	option interface	'lan'
	list prefix		''
	option ignore		1

config rdnss
	option interface	'lan'
	# If not specified, the link-local address of the interface is used
	list addr		''
	option ignore		1

config dnssl
	option interface	'lan'
	list suffix		''
	option ignore		1

root@OpenWrt:~# cat /proc/sys/net/ipv6/conf/pppoe-wan/accept_ra
2
root@OpenWrt:~# cat /proc/sys/net/ipv6/conf/pppoe-wan/forwarding
1
root@OpenWrt:~# cat /proc/sys/net/ipv6/conf/br-lan/accept_ra
1
root@OpenWrt:~# cat /proc/sys/net/ipv6/conf/br-lan/forwarding
1

root@OpenWrt:~# rdisc6 -1 pppoe-wan
Soliciting ff02::2 (ff02::2) on pppoe-wan...

Hop limit                 :           64 (      0x40)
Stateful address conf.    :           No
Stateful other conf.      :          Yes
Mobile home agent         :           No
Router preference         :       medium
Neighbor discovery proxy  :           No
Router lifetime           :         1800 (0x00000708) seconds
Reachable time            :        60000 (0x0000ea60) milliseconds
Retransmit time           :        30000 (0x00007530) milliseconds
 Source link-layer address: 00:30:88:1F:2B:A7
 MTU                      :         1492 bytes (valid)
 Prefix                   : 2003:40:xxxx:xxxx::/64
  On-link                 :          Yes
  Autonomous address conf.:          Yes
  Valid time              :        14400 (0x00003840) seconds
  Pref. time              :         1800 (0x00000708) seconds
 from fe80::230:xxxx:xxxx:1411