Hello Bastian, > - Neighbor sollicitations between the host and the CentOS VMs are being > exchanged regularly > > - With the Debian guest: > > - Neighbor sollicitations are exchanged when the VM is rebooted > > - Afterwards they are not exchanged... > > - ... unless one explicitly pings the guest from the host on this internal > > ULA address > > (then, one can see the echo packets, but also some routerneighbor > > sollicitations) > > You need periodic router advertisements to refresh prefix infos. How > are you generating those?
I assume that they are sent by libvirt since I can see them on the host (with tcpdump) and on the CentOS/RHEL VMs, which are staying connected. I can also see the Debian VM receiving some neighbor sollicitations, as long as it is still connected, but not the ones about itself (except when it is being pinged from the host). Do you mean that something should also run on the guest? > > iface br0 inet6 static > > bridge_ports enp1s0f0 > > address 2001:XXXX:XXXX:XXXX::/56 > > You should always use /64 on an ipv6 network. Yes, this is my understanding. But this is the configuration of the provider of the physical host (OVH) and there are issues on some of their servers if we switch to /64. More generally their IPv6 is a bit unreliable and heterogeneous, especially on the Debian 10 image they provide (with cloud-init configs). But this is the public bridge, that is only used by the public interfaces of the VMs. The issue here is with the internal virtual ULA networks provided by libvirt. I provided this config only for completion, in case there may be side-effects. > > iface enp1s0 inet6 static > > address 2001:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY/64 > > post-up ip route add YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:ff dev enp1s0 > > post-up ip route add 2000::/3 via 2001:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:ff > > dev enp1s0 > > pre-down ip route del 2001:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:ff dev enp1s0 > > pre-down ip route del 2000::/3 via 2001:YYYY:YYYY:YYYY:YYYY:YYYY:YYYY:ff > > dev enp1s0 > > This does not match your description. Please don't change ip addresses > if you are searching for problems. This guest-side configuration is for the public interface and is also provided for completion. The config for the interface to the internal ULA network which is autoconfigured is just this one line: iface enp2s0 inet6 auto It works as expected after a reboot, or if I run: systemctl restart networking But then 'ip a' shows the lifetime decreasing and decreasing from 3600, and in the end the IP address (which is EUI-64 generated, so always the same) vanishes. Should I install additional packages on the guest? It is is a quite minimal Debian install, with just freeipa-client (and dependencies) + apache2 added. Or enable some additional services? Thank you! Mathieu PS: I was not sure whether this ipv6 list is still active, so I also posted on the users list. I hope this is not a problem.
