Problem with a private network in Proxmox 6.1-5

[Tony Krops]

Hello I have a problem with a private network in Proxmox 6.1-5.

The error occurs sporadically when I restart the Guest Server. The Guest Server does not get a connection to the Internet and cannot take the IP 10.10.10.50 for example. I have to change the IP to another one first. For example 10.10.10.51, now everything works fine again, then I can also restart the Guest Server and change the IP back to 10.10.10.50. Everything works as it should again, until after a few restarts it occurs again.

If I leave the IP on 10.10.10.51, the same problem occurs after some restarts.

The IP 10.10.10.50 and the IP are of course only example IPs I have tried it with many different IPs, but it always happens the same error.

Also important to mention is that the error occurs sporadically, so the error does not occur after every restart.

Spoiler: Proxmox /etc/network/interfaces

root@prx1:~# cat  /etc/network/interfaces
# Loopback device:
auto lo
iface lo inet loopback

# device: eth0
auto enp0s31f6
iface enp0s31f6 inet static
  address (IPV4)
  netmask 255.255.255.192
  pointopoint (IPV4)
  gateway (IPV4)

iface enp0s31f6 inet6 static
  address (IPV6)::1
  netmask 128
  gateway fe80::1
  up sysctl -p

auto vmbr0
iface vmbr0 inet static
  address (IPV4)
  netmask 255.255.255.192
  bridge_ports none
  bridge_stp off
  bridge_fd 0
  up ip route add (IPV4)/32 dev vmbr0
  up ip route add (IPV4)/32 dev vmbr0
  up ip route add (IPV4)/32 dev vmbr0
  up ip route add (IPV4)/32 dev vmbr0
  up ip route add (IPV4)/32 dev vmbr0

iface vmbr0 inet6 static
  address (IPV6)::2
  netmask 64
  up ip -6 route add (IPV6)/64 dev vmbr0

#the private Network
auto vmbr1
iface vmbr1 inet static
        address 10.10.10.1
        netmask 255.255.255.0
        bridge_ports none
        bridge_stp off
        bridge_fd 0

And the following is set on the guest Ubuntu-18.04.3 server.

Spoiler: Guest /etc/network/interfaces

root@dev01:~# cat /etc/network/interfaces
source /etc/network/interfaces.d/*

auto ens18
iface ens18 inet static
  address (IPV4)/24
  gateway (IPV4)
  dns-nameservers 1.1.1.1
  dns-nameservers 1.0.0.1

iface ens18 inet6 static
  address (IPV6)::6
  netmask 64
  gateway (IPV6)::2

#the private network
auto ens19
iface ens19 inet static
  address 10.10.10.50/24
  gateway 10.10.10.1

Spoiler: Guest journalctl -u systemd-networkd.service

root@dev01:~# journalctl -u systemd-networkd.service
-- Reboot --
Dez 27 11:57:15 sh2401 systemd[1]: Starting Network Service...
Dez 27 11:57:15 sh2401 systemd-networkd[788]: br0: netdev ready
Dez 27 11:57:15 sh2401 systemd-networkd[788]: Enumeration completed
Dez 27 11:57:15 sh2401 systemd[1]: Started Network Service.
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens19: Link is not managed by us
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens18: Link is not managed by us
Dez 27 11:57:15 sh2401 systemd-networkd[788]: lo: Link is not managed by us
Dez 27 11:57:15 sh2401 systemd-networkd[788]: br0: IPv6 successfully enabled
Dez 27 11:57:15 sh2401 systemd-networkd[788]: lo: Link is not managed by us
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens18: IPv6 successfully enabled
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens19: IPv6 successfully disabled
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens18: Gained carrier
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens19: Gained carrier
Dez 27 11:57:15 sh2401 systemd-networkd[788]: br0: Gained carrier
Dez 27 11:57:15 sh2401 systemd-networkd[788]: ens19: Configured
Dez 27 11:57:16 sh2401 systemd-networkd[788]: ens18: Gained IPv6LL
Dez 27 11:57:16 sh2401 systemd-networkd[788]: ens18: Could not set route: Network is unreachable
Dez 27 11:57:16 sh2401 systemd-networkd[788]: ens18: Configured
Dez 27 11:57:17 sh2401 systemd-networkd[788]: br0: Gained IPv6LL
Dez 27 11:57:17 sh2401 systemd-networkd[788]: br0: Configured
Dez 27 11:57:18 sh2401 systemd-networkd[788]: tun0: Gained carrier
Dez 27 11:57:18 sh2401 systemd-networkd[788]: tun0: Gained IPv6LL

I hope the problem has become clear, if not please feel free to ask me. I would be very happy about help.
It is my first forum post here, if you want to see any other logs or configs please tell me how to get them for you and I will get them for you.

If someone would like to answer in German he can also write to me.

 

[Stefan_R]

The Guest Server does not get a connection to the Internet and cannot take the IP 10.10.10.50 for example.

Well, it can't get a connection to the internet if the vmbr1 (which I assume corresponds to 'ens19' in the guest?) interface doesn't have any bridge-ports...

I assume you mean it also cannot connect to other devices on the same bridge? (i.e. in the same 10.10.10.1/24 subnet)
If so, what exactly happens when it 'cannot take the IP'? Can you ping devices? Can you connect to 10.10.10.1, i.e. the PVE host? What does ip addr say? ip link? (on the guest)

Also, you can run tcpdump -i vmbr1 on the PVE host to see what traffic is coming (or not coming) from your VMs.