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Occasional loss of IPv6 router advertisements

bllfr0g

New Around Here
I've got an AC-86U.

Every once in a while, dnsmasq stops sending out IPv6 router advertisements. It's pretty infrequent; I first noticed it in December after upgrading to 384.8 (I'm on 384.11_2 now) and it's happened maybe a total of 4 times since then. When it happens, dns resolution still seems to work, and dnsmasq responds to router solicitations, but it doesn't send out the unsolicited RAs every 10 seconds like it's supposed to. As a result my machine loses its IPv6 address after 10 minutes.

A reboot of the router resolves the issue. So far, no discernible pattern as to when it happens.

Anyone else seeing this?
 

universe83

Occasional Visitor
I've got an AC-86U.

Every once in a while, dnsmasq stops sending out IPv6 router advertisements. It's pretty infrequent; I first noticed it in December after upgrading to 384.8 (I'm on 384.11_2 now) and it's happened maybe a total of 4 times since then. When it happens, dns resolution still seems to work, and dnsmasq responds to router solicitations, but it doesn't send out the unsolicited RAs every 10 seconds like it's supposed to. As a result my machine loses its IPv6 address after 10 minutes.

A reboot of the router resolves the issue. So far, no discernible pattern as to when it happens.

Anyone else seeing this?
AC86U. Stock firmware 45713.
The same happens to me.
 

CriticJay

Senior Member
I thought it was just me! Yes, I do see this behaviour on all firmwares (Merlin and non-Merlin) for the past 6-10 months or so.

In terms of client devices, I see it most often on Win7 / Win10 machines - and occasionally on other smart devices such as Android (Chromecast) or IoT (NEST thermostat). Curiously though, I've never seen this phenomenon on my iOS or MacOS devices.
 

Latzz

Regular Contributor
Stable IPv6 with zero issues for over a year with the AC86U. Some ISPs are still known to have issues with IPv6 implementations thus making it more difficult to isolate if its firmware related.
 

CriticJay

Senior Member
Stable IPv6 with zero issues for over a year with the AC86U. Some ISPs are still known to have issues with IPv6 implementations thus making it more difficult to isolate if its firmware related.
But the issue from the OP is: "Every once in a while, dnsmasq stops sending out IPv6 router advertisements."

Is it possible that an ISP with a flaky IPv6 implementation can impact dnsmasq like that?
 

Kolya

New Around Here
I just saw the same thing a few days ago with Asuswrt Merlin version 384.17 on a ASUS RT-AC68U.

I am pretty sure that router advertisements stopped being sent. When I logged into the router admin web page and toggled "Enable Router Advertisement" on and off on the IPv6 settings page (applying each time) my ethernet interface was once again allocated IPV6 addresses (on a Windows 10) machine.

Next time this happens I'd be tempted to attach to the dnsmasq process on the router via the strace facility but unfortunately strace is not available. I wonder how hard it would be to get a version of dnsmasq compiled and linked with symbols. Then it might be possible to send a signal to the dnsmasq process and force it to dump core and then take a look at it's internal state variables in a debugger.
 

Dabombber

Senior Member
Is there anything in the logs about dhcp6c when this happens, if the start_dhcp6c event is being skipped you'll lose IPv6. Does restarting the client (or even just the network adapter) fix the problem, there could have been a change in IPv6 address but the client is still using the old gateway.

Neither sounds exactly like what you're experiencing, but they're both problems I've come across.
 

Kolya

New Around Here
My router log files tend to wrap around because I am logging packets dropped by the firewall. I guess I could log from the router to another computer so everything would be preserved for analysis after events like this. I use Comcast - they don't typically change the ipv6 address / prefix allocated to your router unless your router changes it's MAC address or if it stays off their network for a long time.
 

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