NAT Proxmox fails


Apr 4, 2018
I continue with the topic of networks. I have a practical case, this time is to create a network (for a hypothetical company) and divide it into several subnets. The most normal thing would be to divide it with the mask but if one computer changes the mask the others will be seen.

So it occurred to me to use several Nat = range of Private IPs that share the same Public IP. With a DHCP Server in LXC with Debian to give the IPs of each network.

following the official Wiki:

auto vmbr0
iface vmbr0 inet static
        bridge-ports enp4s0f0
        bridge-stp off
        bridge-fd 0

auto vmbr4
iface vmbr4 inet static
        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 '' -o vmbr0 -j MASQUERADE
        post-down iptables -t nat -D POSTROUTING -s '' -o vmbr0 -j MASQUERADE

Work works. Give the IPs and have Internet access. But I create an another NAT (vmbr3 - and this happen:

  • From the machines in NAT (both networks: and you can see the other machine in LAN with
  • From you can not see any of the NAT networks. Neither nor
  • From the NAT machines they see each other even though they are in different networks: From to and successively.
My doubt is that because they see these two networks if they should be separated. And how to properly do the division.

Thanks all !


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