Public IPv6 Bridges

André Malm admin at
Sat Jan 7 20:48:15 UTC 2023

I'm having trouble getting IPv6 to work for my KVM/qemu guests.

I have two bridges setup, one routed (external, non libvirt) bridge for 
public dedicated ipv4 + ipv6 which works for both protocols.

Then I have a libvirt nat bridge (with the routed bridge as parent) with 
a nated ipv4 (that works) and I also want a public ipv6. I'm able to 
transmit udp packets out but I never get any response.

Looking at tcpdump there are incoming neighbor solicitations that get 
unanswered and don't get forwarded to the guest.

Do I need to set something special up for this to work? Ubuntu 22.04 / 
Libvirt 8.0.0

The routed bridge (pubBr) has ipv6 2001:x:x:7d8e:: - My nat bridge 
config below:

     <bridge name="natbr" />
     <forward mode='nat' dev='pubBr'>
         <port start='8000' end='30000'/>
     <ip address="" netmask="">
         <range start='' end=''/>
     <ip family="ipv6" address="2001:x:x:7d8e::1" prefix="64">
         <host name="test" ip="2001:x:x:7d8e:a01:2ff::"/>


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