IPv6 config giving log error message

[strubbly]

I'm using John's brilliant Asuswrt-Merlin 374.43 LTS fork (latest release). I'm trying to set up IPv6. My ISP is BT in the UK. The settings that work seem to be mostly simple or default:

Connection Type: Native
Interface: PPP
DHCP-PD: enable
MTU: 1492​

LAN Settings

LAN Prefix Length: 56
Auto Configuration: Stateless​

Auto Configuration Setting

Enable Router Advertisement: Enable
Enable DHCPv6 Server: Disable​

Special ISP Options

Enable IPv6 MTU advertisement: Yes
Release addresses on exit: Yes
Prefix delegation requires address request: Yes​

These seem to me to be mostly default or obvious except the very last one - which is the one giving me a problem.

If I set it to Yes, then I get IPv6 working but my log fills up with these messages - about 1 a second:

dhcp6c: dhcp6c state change detected SOLICIT​

Apart from the log messages, everything else seems to be working. My router doesn't get a global WAN IPv6 address but apparently BT don't provide one anyway. I think what's happening is that the router is using SOLICIT to try to get a WAN side address but not getting one.

If I set it to No then the log messages stop but I lose the Prefix and IPv6 Gateway and IPv6 stops working.

Any ideas on how to stop this log message and presumably all the wasted SOLICIT messages? I've tried quite a lot of other settings but nothing else seems to work. Maybe I need to add a script to configure something, though I don't know what might be needed at all.

 

[strubbly]

So, just in case anyone comes to this thread in the future, I seem to finally have a solution.

To get IPv6 working on BT, all the settings are pretty much default except

Prefix delegation requires address request: Yes

Note that above I have Enable DHCPv6 Server: Disable but I changed that back to Enable. That wasn't the problem.

That all seems to work but also I get the above mentioned log messages - a couple a second. I actually had that running for a long time and just ignored the log - most things seemed to be working. But I finally looked at the log problem again and found what seems to be a more sensible fix which is in the nvram options. It seems I need to disable rapid-commit for dhcp6c client. I don't really know why but that seems to work. So I SSH in and enter

nvram set ipv6_isp_opt=8
nvram commit && reboot

and my log no longer fills up with rubbish. While it's possible I may still have something wrong, I'm getting proper IPv6 on all my clients and the log looks good so I think that's right.

 

[john9527]

@strubbly

I think I'm going to faint! Someone who actually takes the time to read the documentation!!!

It was a while back, but the ipv6_isp_opt settings were put in when I was working with someone in the UK on IPv6. While it looks like things have settled down quite a bit, there's still some variation in how the ISPs implement IPv6. Congratulation on working it out for your use case and thanks for taking the time to document what you found.

 

[heysoundude]

Someone who actually takes the time to read the documentation!!!

is it safe to assume there is similar documentation for Merlin? a manpage somewhere?

 

[john9527]

is it safe to assume there is similar documentation for Merlin? a manpage somewhere?

In this case, the 'doc' is a text file I package with every release that lists options which at the time of release are unique to my fork. It includes info on nvram only (no gui) options that have been included either for debug purposes or to address special requirements that most users would not need. The ipv6_isp_opt settings the op used are an example.

 

[heysoundude]

I was curious to see...no, AM curious to see what options there are in case I should ever want or need to make changes. I just don't know where I'd look for that info