Re: Debian VMs on a routed libvirt ULA network are not exchanging neighbor sollicitations with the host

Hi Mathieu

On Tue, Mar 16, 2021 at 10:23:15AM +0100, Mathieu Baudier wrote:
> What I can observe is that:
> - 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?

> iface br0 inet6 static
>  bridge_ports enp1s0f0
>  address 2001:XXXX:XXXX:XXXX::/56

You should always use /64 on an ipv6 network.

> 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.

Bastian