[SOLVED] IPv6 on 378.55_0 kills DHCP

[Endre Czirbesz]

I have recently upgraded my AC68U to 378.55_0, which works fine, so far.

I've run into a problem, and I'm not sure if I'm doing something wrong, or there is an issue.

I've used a Hurricane Electrinc IPv6 tunnel previously on 376.49_4, so I tried to set it up again, but I could not make it work. If I enable IPv6 on the router, DHCP (v4) stop working, my clients does not get any IP address, and also there is no name resolution on the router itself. DHCP6 does not seem to work either.

Am I doing something wrong? Should I change some other settings as well for IPv6 tunnelling?

Thanks for any help in advance.

Endre

 

[SnakeByte]

This happened to me too. Same model and firmware version.

 

[charlie2alpha]

Which means dnsmasq on the router malfunctions, since it is that daemon which handles both of these.

 

[Endre Czirbesz]

So, I had some time to dig deeper. When I enable IPv6, dnsmasq fails to start with an error:

dnsmasq: bad IPv6 address at line 26 of /etc/dnsmasq.conf

That line is

dhcp-option=dnsf11,option6:23,[8.8.8.8]

That is definitely not an IPv6 address, and it happens to be Google's DNS server, which I used previously on the LAN - DHCP Server page as DNS Server 1. If I remove this setting, everything seems to work fine.

It looks like a bug for me, as it should not be put in dnsmasq.conf, but I can live with this workaround.

 

[RMerlin]

Check your tunnel configuration. It's working for me, this is what my dnsmasq contains:

dhcp-option=lan,option6:23,[::]

Option 23 should contain an IPv6 DNS server, or be left blank if you use your ISP's DNS.

 

[Endre Czirbesz]

Check your tunnel configuration. It's working for me, this is what my dnsmasq contains:

dhcp-option=lan,option6:23,[::]

Option 23 should contain an IPv6 DNS server, or be left blank if you use your ISP's DNS.

I have that line in my dnsmasq config, but I also had an extra line with my IPv4 DNS from the DHCP server page. So it seems, if you have a DNS server set on the DHCP settings page before you turn on IPv6, that DNS gets into the dnsmasq.conf as

dhcp-option=dnsf11,option6:23,[8.8.8.8]

 

[revnull]

I know this thread is listed as solved, but I'm having the same or similar problem on my RT-N66U using Merlin 380.57. I've already tried a full reset and manual re-config.

Feb  7 20:50:33 rc_service: watchdog 254:notify_rc start_dnsmasq
Feb  7 20:50:33 dnsmasq[1519]: bad IPv6 address at line 23 of /etc/dnsmasq.conf
Feb  7 20:50:33 dnsmasq[1519]: FAILED to start up

Line 23 of /etc/dnsmasq.conf

dhcp-option=dnsf11,option6:23,[8.8.8.8]

Disabling IPv6 resolves the problem. Any ideas?

 

[revnull]

I can also confirm that removing (blanking) the "DNS Server 1" entry in the "LAN - DHCP Server" section is a valid workaround. The "dnsf11" entry on line 23 is not missing from the dnsmasq.conf and dnsmasq has stopped crashing.

Thanks to Endre for the workaround. I agree, this seems to be a bug.

 

[PabloAbonia]

Try changing it to:

dhcp-option=dnsf11,option6:dns-server,[2001:4860:4860::8888]

You need to use "dns-server" rather than "23" as the number doesn't work properly. You also need an IPv6 rather than IPv4 address

Pablo

 

[revnull]

Yes, when I tried editing the dnsmasq.conf directly it gets overwritten with the previous incorrect values when the watchdog restarts the service.

 

[RMerlin]

Yes, when I tried editing the dnsmasq.conf directly it gets overwritten with the previous incorrect values when the watchdog restarts the service.

https://github.com/RMerl/asuswrt-merlin/wiki/Custom-config-files

 

[revnull]

The problem seems to be that part of the IPv4 config is being added to the IPv6 dnsmasq config. Since removing the 1st custom DNS entry fixes this and it's reproducible, I would consider this a bug.

Sent from my Nexus 6P using Tapatalk

 

[RMerlin]

The problem seems to be that part of the IPv4 config is being added to the IPv6 dnsmasq config. Since removing the 1st custom DNS entry fixes this and it's reproducible, I would consider this a bug.

Sent from my Nexus 6P using Tapatalk

Might be, but since I can't test IPv6, I leave any work on that code to Asus.