first stretch vm in proxmox

[mj <lists@merit.unu.edu>]

Hi,

I just created a first test installation of stretch in a VM on proxmox. 
Installation goes fine, with a netinst cd. Network (dhcp) works, 
packages are downloaded, etc, etc.

However, after the initial boot, there is no network anymore. :-(

Tried an install with GUI, and one without. Both have the same issue. I 
cannot even ping my default gw. However:

ip route list gives the expected output
ip -a gives the correct ip address
/etc/resolv.conf contains my dns servers

Everything seems correct, but no packets flow, not even a ping to the 
default gw, while during the install, everything works.

Any tips or ideas where to look at?

MJ