Got it working but had to switch thing up, in case it help someone.

[UbioZur]

First of all, Thank you SO MUCH for the guide!

I have flashed openwrt on a TPLink archer AX23 v1.20

I do not know which ISP I have (my partner doesn't know either). but it is IPv6 MAP-e. and IP prefix is 240b:XX::, also the ip6prefixlen is 31 !

By following the guide to the letter, I could not get it to work. For my own log, and in case it help someone, I will write the full step by step here:

• grab from ISP router: MAC address of WAN, IPv6/Map-E info

• grab from the online calculator all the information

• grab map.sh.new

• flash fresh openwrt

• Set wan device MAC address to the original router (just to be sure)

• Disconect original router (can't have two devices on the same internet plug)

• connect wan to internet (no ISP router), and LAN to computer

• check internet ping6 ipv6.google.com

• update openwrt packages opkg update && opkg list-upgradable | cut -f 1 -d ' ' | xargs -r opkg --force-overwrite upgrade (Careful, it is not adviced! I did it because it was a fresh openwrt install)

• install map packages opkg install map

• reboot router

• check internet ping6 ipv6.google.com (Yes I am poranoid, It took me for ever to get it working)

• follow guide to setup wan6 HOWEVER use the option ip6prefix '240b:aa:bbbb:cccc::/64'. If following the guide exactly (or my understanding of it) option ip6prefix '240b:aa::/31'will result on the ipv4 connection not functioning. I used the IPv6 glocal address from the original router to know the values ofbbbb:cccc`

• Follow the guide for LAN.

• NOTE: while the client have a global IPv6, it cannot get DNS for some reasons, in relay mode. for now just use ip to check conection

• check router connection ping6 2001:4860:4860::8888

• check client connection ping6 2001:4860:4860::8888

• follow the guide for WAN6MAPE use the ip6prefix 240b:aa:: and ip6prefixlen 31 just like the calculator tool show.

• send the new map.sh to the router

• reboot router

• check the ips on the webgui interface.

• check connection in ipv6 ping6 2001:4860:4860::8888 ipv4 ping 8.8.8.8 dns ping ipv6.google.com ping google.com

• check the OCN verification page ( I had to use different browser than firefox to see my ipv6, probably a configuration in my firefox ).

• I believe nichiban.co.jp is down, I cannot access it with computer or even phone on LTE. so I don't know if the ports and amount of connection are ok.

I hope it can help someone not spend for ever (I have tried many many times to get this to work over the past few years), but that difference between the using a /64 address instead of the calculator /31 for the wan6 interface, made all the difference!

[LIII-XXII]

about the website, use https://www.nichiban.co.jp/

normally https://nichiban.co.jp/ would redirect but don't ask me why it won't 🤷

[UbioZur]

I had to tweak a few more things.
Some websites (banks login, github container registry etc) where not accessible. MTU issues for some reasons.

To share in case other people have the same issue.

WAN6MAPE interface -> Advanced settings -> Use MTU on tunnel interface 1460

Network -> Firewall -> Flow offloading type Off (apparently the software and hardware bypass the MSS clamp

Network -> Firewall -> zone, for each zone that deal with wan -> MSS Clamping on

Network -> Firewall -> zone, lan to wan and guest to wan -> Forward ACCEPT

on openwrt router (ssh)

nft list table inet mape

it only showed 1 chain -> chain srcnat
so I had to setup another chain to the firewall to make MSS clamping working

System -> Startup -> Local Startup

# Start a background loop so it doesn't block the rest of the boot process
(
    for i in $(seq 1 30); do
        # Check if the 'mape' table has been created by the ISP script yet
        if nft list tables | grep -q "inet mape"; then
            # Table found! Add the chain and rule
            nft add chain inet mape legacy_forward { type filter hook forward priority 0 \; }
            nft add rule inet mape legacy_forward oifname "map-WAN6MAPE" tcp flags syn tcp option maxseg size set 1420
            logger -t "MTU_FIX" "MSS Clamping applied to inet mape table."
            break
        fi
        # If not found, wait 5 seconds and try again
        sleep 5
    done
) &

Make sure to reboot the router.

now on the router via ssh tcpdump -i any host github.com and 'tcp[tcpflags] & (tcp-syn) != 0' -v

on a client on the network run a wget to check (i used) wget https://github.com/VSCodium/vscodium/releases/download/1.112.01907/vscodium-reh-linux-x64-1.112.01907.tar.gz

Maybe it is possible to use wget -O /dev/null http://speedtest.tele2.net/100MB.zip but. I didn't check if it was blocked before.

No more issues to download from ghcr.io and lscr.io etc... I can remote connect with vscodium and it does install the server and plugins.

All of my issues are fixed! I wish it wouldn't require so much tinkering to have a proper router in Japan!

Hopefully this can help someone else if they have the same issue.