[clug] IPv6, KVM and bridge interfaces

Edward C. Lang edlang at edlang.org
Tue Jul 17 04:50:21 MDT 2012

On Sun, Jul 15, 2012 at 09:45:35PM +1000, Edward C. Lang wrote:
> Hi,
> I'm having some problems with IPv6 and my Ubuntu KVM host. I can't get to the automatically discovered router:
> [...]
> Any ideas as to what's gone wrong? For what it's worth, the Ubuntu server
> is also connected to a wireless bridge. The bridge is running Tomato and
> doesn't have an IPv6 address. The main router (to which the Windows
> computer is connected) is running openwrt and radvd. There's no firewall
> configured on the Ubuntu server.

The issue appears to lie with my router that's acting as a wireless

root at rt-n16:/tmp/home/root# ip -6 a s br0 dynamic
27: br0: <BROADCAST,MULTICAST,UP,10000> mtu 1500
    inet6 2001:db8::e2cb:4eff:fec0:f97/64 scope global dynamic
       valid_lft 86282sec preferred_lft 14282sec
root at rt-n16:/tmp/home/root# ip r g 2600:3c02::f03c:91ff:fe96:18b8
2600:3c02::f03c:91ff:fe96:18b8 via fe80::92f6:52ff:fef6:1082 dev br0  proto kernel  src 2001:db8::e2cb:4eff:fec0:f97  metric 1024  expires 1662sec mtu 1500 advmss 1440 metric 10 64
root at rt-n16:/tmp/home/root# ping6 -c 1 edlang.org
PING edlang.org (2600:3c02::f03c:91ff:fe96:18b8): 56 data bytes

--- edlang.org ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss

These exact same commands where they do work:

root at OpenWrt:~# ip -6 a s br-lan dynamic
28: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
    inet6 2001:db8::92f6:52ff:fef6:1082/64 scope global dynamic
       valid_lft 86344sec preferred_lft 14344sec
root at OpenWrt:~# ip r g 2600:3c02::f03c:91ff:fe96:18b8
2600:3c02::f03c:91ff:fe96:18b8 from :: via fe80::221:a0ff:febb:3200 dev pppoe-wan  src 2001:db8::200:ff:fe00:0  metric 0
root at OpenWrt:~# ping6 -c 1 2600:3c02::f03c:91ff:fe96:18b8
PING 2600:3c02::f03c:91ff:fe96:18b8 (2600:3c02::f03c:91ff:fe96:18b8): 56 data bytes
64 bytes from 2600:3c02::f03c:91ff:fe96:18b8: seq=0 ttl=51 time=312.070 ms

--- 2600:3c02::f03c:91ff:fe96:18b8 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 312.070/312.070/312.070 ms

I can't see anything suspicious in the firewall configuration on the
RT-N16 ... 



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