I tested with a different router and with LEDE 17.01.7 (TP-Link WDR4300 v1.7).
Everything works out of the box. There is no WAN_6 grayed out bugged inferface - it modifies the existing WAN6 config automatically as needed, without adding the unnecessary and unchangeable WAN_6
IPv6 works with WAN6, without me doing anything other than changing the protocol to PPPoE and entering the login and password, and save+apply.
Now, tell me again, this is not a bug in the OpenWrt 19.07.1
tcpdump -vvvni any ip6 and udp port 546 &
odhcp6c pppoe-wan
shows this:
13:33:17.559071 ethertype IPv6, IP6 (hlim 1, next-header UDP (17) payload length: 93) fe80::89cc:874d:e516:7306.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=dcc424 (elapsed-time 6300) (client-ID hwaddr/time type 1 time 491624195 d8cb8a1e885e) (IA_NA IAID:64539530 T1:0 T2:0) (Client-FQDN) (vendor-class) (option-request DNS-search-list DNS-server vendor-specific-info Client-FQDN))
13:33:17.559084 IP6 (hlim 1, next-header UDP (17) payload length: 93) fe80::89cc:874d:e516:7306.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=dcc424 (elapsed-time 6300) (client-ID hwaddr/time type 1 time 491624195 d8cb8a1e885e) (IA_NA IAID:64539530 T1:0 T2:0) (Client-FQDN) (vendor-class) (option-request DNS-search-list DNS-server vendor-specific-info Client-FQDN))
13:33:21.355096 ethertype IPv6, IP6 (flowlabel 0x645bc, hlim 1, next-header UDP (17) payload length: 103) fe80::8caf:3ba7:ca0b:c42e.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=3d03d6 (elapsed-time 3103) (client-ID hwaddr/time type 1 time 593056730 3cd92b60f763) (IA_NA IAID:138205483 T1:0 T2:0) (Client-FQDN) (vendor-class) (option-request vendor-specific-info DNS-server DNS-search-list Client-FQDN))
13:33:21.355115 IP6 (flowlabel 0x645bc, hlim 1, next-header UDP (17) payload length: 103) fe80::8caf:3ba7:ca0b:c42e.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=3d03d6 (elapsed-time 3103) (client-ID hwaddr/time type 1 time 593056730 3cd92b60f763) (IA_NA IAID:138205483 T1:0 T2:0) (Client-FQDN) (vendor-class) (option-request vendor-specific-info DNS-server DNS-search-list Client-FQDN))
13:33:22.399908 ethertype IPv6, IP6 (hlim 64, next-header UDP (17) payload length: 74) fe80::c225:e9ff:fe9a:4e5d.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=fe60b7 (client-ID hwaddr/time type 1 time 636298372 c025e99a4e5d) (IA_NA IAID:5587076 T1:0 T2:0) (elapsed-time 2970) (option-request DNS-server) (IA_PD IAID:5587075 T1:0 T2:0))
13:33:22.399923 IP6 (hlim 64, next-header UDP (17) payload length: 74) fe80::c225:e9ff:fe9a:4e5d.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=fe60b7 (client-ID hwaddr/time type 1 time 636298372 c025e99a4e5d) (IA_NA IAID:5587076 T1:0 T2:0) (elapsed-time 2970) (option-request DNS-server) (IA_PD IAID:5587075 T1:0 T2:0))
13:33:27.699988 ethertype IPv6, IP6 (hlim 64, next-header UDP (17) payload length: 74) fe80::c225:e9ff:fe9a:4e5d.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=7d49ed (client-ID hwaddr/time type 1 time 636298407 c025e99a4e5d) (IA_NA IAID:5587110 T1:0 T2:0) (elapsed-time 0) (option-request DNS-server) (IA_PD IAID:5587109 T1:0 T2:0))
13:33:27.700001 IP6 (hlim 64, next-header UDP (17) payload length: 74) fe80::c225:e9ff:fe9a:4e5d.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=7d49ed (client-ID hwaddr/time type 1 time 636298407 c025e99a4e5d) (IA_NA IAID:5587110 T1:0 T2:0) (elapsed-time 0) (option-request DNS-server) (IA_PD IAID:5587109 T1:0 T2:0))
Ping works:
root@LEDE:~# ping ipv6.icanhazip.com
PING ipv6.icanhazip.com (2a01:4f8:c0c:4925::10): 56 data bytes
64 bytes from 2a01:4f8:c0c:4925::10: seq=0 ttl=54 time=38.013 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=1 ttl=54 time=37.836 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=2 ttl=54 time=37.750 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=3 ttl=54 time=37.917 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=4 ttl=54 time=37.781 ms
^C
--- ipv6.icanhazip.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 37.750/37.859/38.013 ms
root@LEDE:~# ping ipv4.icanhazip.com
PING ipv4.icanhazip.com (104.20.16.242): 56 data bytes
64 bytes from 104.20.16.242: seq=0 ttl=61 time=7.269 ms
64 bytes from 104.20.16.242: seq=1 ttl=61 time=7.346 ms
64 bytes from 104.20.16.242: seq=2 ttl=61 time=7.578 ms
64 bytes from 104.20.16.242: seq=3 ttl=61 time=7.273 ms
64 bytes from 104.20.16.242: seq=4 ttl=61 time=7.296 ms
64 bytes from 104.20.16.242: seq=5 ttl=61 time=7.256 ms
64 bytes from 104.20.16.242: seq=6 ttl=61 time=7.262 ms
64 bytes from 104.20.16.242: seq=7 ttl=61 time=7.234 ms
64 bytes from 104.20.16.242: seq=8 ttl=61 time=7.307 ms
^C
--- ipv4.icanhazip.com ping statistics ---
9 packets transmitted, 9 packets received, 0% packet loss
round-trip min/avg/max = 7.234/7.313/7.578 ms
root@LEDE:~#
I will now save the TP-Link backup and will attempt to use it with my Xiaomi router.
Update....
I upgraded my router with LEDE 17.01.7 (TP-Link WDR4300 v1.7) > OpenWrt 19.07.1 and keeping the settings.
And this is the result:
root@LEDE:~# ping ipv4.icanhazip.com
PING ipv4.icanhazip.com (104.20.17.242): 56 data bytes
64 bytes from 104.20.17.242: seq=0 ttl=61 time=7.314 ms
64 bytes from 104.20.17.242: seq=1 ttl=61 time=7.322 ms
64 bytes from 104.20.17.242: seq=2 ttl=61 time=7.285 ms
^C
--- ipv4.icanhazip.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 7.285/7.307/7.322 ms
root@LEDE:~# ping ipv6.icanhazip.com
PING ipv6.icanhazip.com (2a01:4f8:c0c:4925::10): 56 data bytes
64 bytes from 2a01:4f8:c0c:4925::10: seq=0 ttl=54 time=38.024 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=1 ttl=54 time=37.744 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=2 ttl=54 time=37.791 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=3 ttl=54 time=37.898 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=4 ttl=54 time=37.711 ms
64 bytes from 2a01:4f8:c0c:4925::10: seq=5 ttl=54 time=37.761 ms
^C
--- ipv6.icanhazip.com ping statistics ---
6 packets transmitted, 6 packets received, 0% packet loss
round-trip min/avg/max = 37.711/37.821/38.024 ms
root@LEDE:~#
Still everything works.
So is the solution indeed to downgrade to LEDE 17.01.7, factory reset, enter the settings and then upgrade back to OpenWrt 19.07.1 ..?
This one has a proper WAN6 interface and a virtual WAN_6 interface that actually works.
Update 2...
I have noticed that the stock LEDE 17.01.7 and stock OpenWrt 19.07.1 have different protocols available from the drop-down menu in Interfaces....
Is this what is causing the problems?
LEDE 17.01.7 (pic is from before selecting the protocol PPPoE and entering the login and pass)
OpenWrt 19.07.1