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Assign public available IPv6 adress to every guest

Working IPv6 connectivity suddenly stops working. After starting everything up (network on host, guests) everything works fine. i can connect from the outside via ssh to a guest. i can connect from the guest via ipv6 to the outside and so on. but after several minutes the connection breaks. and ping6 says

Destination unreachable: Address unreachable

i can ping6 the bridge but not the guests anymore

My Setup:
Ubuntu 12.04 with KVM over libvirt.
I have multiple guests running which are connected via IPv4 over a network bridge.
This works fine.
KVM host has reliable IPv6 connectivity.
I assigned via VIRSH an IPv6 address to the bridge.
i use radvd to advertise IPv6 adresses to guests.

i set the following in /etc/sysctl.conf



host /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
iface eth0 inet6 static
address 2a01:dead:beef:a:x:x:x:x
netmask 64
gateway fe80::1

guest /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
iface eth0 inet6 static
address 2a01:dead:beef:a::3
netmask 64
gateway 2a01:dead:beef:a::1 <- this is the ip i assigned to the bridge


now it works like supposed to. i dont know what the problem was. i set it up from scratch. works like a charm. maybe i misconfigured something on the way which interfered. but i cant image what that would be.

share|improve this question
Posisbly related:… – Michael Hampton Jul 18 '12 at 19:01
Are you using native IPv6 from your ISP, or a tunneling service, or 6to4, or something else? – Michael Hampton Jul 18 '12 at 19:02
Im using a native /64 net – user128802 Jul 19 '12 at 12:52
Can you post your interfaces file? – cstamas Jul 19 '12 at 13:07
edited the original post – user128802 Jul 19 '12 at 13:25

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