I recently purchased a Kimsufi instance (a Proxmox distrib' with one public IP and one physical network interface). I want to be able to instantiate several containers/VM that will be reachable from the internet. Given some research online, I thought having a NAT configuration would be suitable for my usage. Once the setup was done, I was able to ping direct IPs but not able to resolve DNS in the containers/VM. I tried adding a DNS server different from the one of the host machine, still not working.

Here are the configurations below, is somebody familiar with this approach ? Any kind of advice/answer would be appreciated.

HOST MACHINE (Proxmox)

/etc/network/interfaces

auto lo
iface lo inet loopback

iface eth0 inet manual

auto vmbr0
iface vmbr0 inet static
    address  MY.PUB.IP.XXX/24         # anonymized on purpose
    gateway  MY.PUB.IP.1              # anonymized on purpose
    bridge_ports eth0
    bridge_stp off
    bridge_fd 0

auto vmbr1
iface vmbr1 inet static
    address 10.10.10.1/24
    bridge_ports none
    bridge_stp off
    bridge_fd 0
    post-up   echo 1 > /proc/sys/net/ipv4/ip_forward
    post-up   iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE
    post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o vmbr0 -j MASQUERADE

Container

/etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 10.10.10.2/24
        gateway 10.10.10.1
        dns-nameservers 8.8.8.8

/etc/resolv.conf

# --- BEGIN PVE ---
nameserver 8.8.8.8
# --- END PVE ---

Output when trying to update machine

root@container:~# apt update     
Err:1 http://security.debian.org bullseye-security InRelease         `
  Temporary failure resolving 'security.debian.org'
Err:2 http://ftp.debian.org/debian bullseye InRelease                
  Temporary failure resolving 'ftp.debian.org'
Err:3 http://ftp.debian.org/debian bullseye-updates InRelease
  Temporary failure resolving 'ftp.debian.org'
Reading package lists... Done    
Building dependency tree... Done
All packages are up to date.
W: Failed to fetch http://ftp.debian.org/debian/dists/bullseye/InRelease  Temporary failure resolving 'ftp.debian.org'
W: Failed to fetch http://ftp.debian.org/debian/dists/bullseye-updates/InRelease  Temporary failure resolving 'ftp.debian.org'
W: Failed to fetch http://security.debian.org/dists/bullseye-security/InRelease  Temporary failure resolving 'security.debian.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.