Interface pi comes up but SSH not available

[drn05r]

The interface pi comes up relatively quickly including the v6 VPN tunnel but if you try to connected to SSH in the first 5-10 minutes of it coming up you get connection refused. Monitoring gives the impression that the local IP address (10.0.0.1) is not up. When the interface pi comes up there also seems to be issues with dhcpd and getting the tablet to connect.

I suspect the problem may be a conflict between /etc/network./nterfaces that configures eth0 staticly and somewhere else that is trying to configure it with dhcp. This is probably as a result of moving to Debain Buster.

It is worth taking a look at which systemd units are marked as faied, As I remember seeing a number of network related units as failed.