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#1 2016-05-11 10:05:40

treysis
Member
Registered: 2009-05-10
Posts: 23

[SOLVED] NetworkManager & IPv6-SLAAC: No DNS acquired

Hello,

After a long time I have installed ArchLinux again. In my network, I am using a router to connect to an IPv6-tunnelbroker (Hurricane Electric) and I advertise the prefix from the tunnel on my network. It works fine with Mint/Ubuntu/Windows. However, ArchLinux sees the router advertisements, assigns itself an IP using SLAAC, assigns the gateway, but it doesn't assign any DNS. I made sure to check the option for automatic DNS in networkmanager. I have two ethernet-interfaces on the machine. One for IPv4-only, and one for IPv6. If I turn on the IPv4-interface, everything works fine, the resolv.conf is updated with the correct IPv4 for the DNS. This DNS is also capable of returning IPv6-addresses, so IPv6 is working (ping -6 www.google.com is fine). If I turn off IPv4-interace, turn on IPv6-interface only, resolv.conf is empty, so I can ping IPv6-addresses, but no hostnames)

Did I miss some configuration?
Do I need some additional networkmanager-plugin? Or extra package like dnsmasq?
Is this a bug of networkmanager?
And most importantly: are there any logs to see what is going on?

Thanks for your help!

PS: I always thought Mint Mate/Ubuntu are using networkmanager as well. But the settings dialogs there look a bit different. Are they using some kind of fork or is it "native" to the Desktop Environment?

Last edited by treysis (2016-05-12 21:54:41)

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#2 2016-05-12 21:54:22

treysis
Member
Registered: 2009-05-10
Posts: 23

Re: [SOLVED] NetworkManager & IPv6-SLAAC: No DNS acquired

Of course I was wrong. SLAAC only advertises prefix and gateway. Why it worked on the other machines? They did the nameserver-lookup via IPv4. It is totally fine for an IPv4-DNS-server to return an IPv6-address (likewise the other way round).
To advertise also additional options like DNS, it is necessary to use "Stateless DHCPv6". In that case the IPv6-address and gateway are acquired from the router advertisements using SLAAC. In those router advertisements there is a flag ('O'-flag). If this is set to 1, then the client will start looking for a DHCPv6-server that sends out additional options. For this, I used a tiny program called "dibbler".

Now everything is working perfectly. If somebody has more specific questions about this topic, I am happy to explain!

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