Proxmox + openvpn, forward internal network?

Question

linux

Good afternoon, please help with advice, I didn’t work with proxmox before,
there is a debian installed on it Proxmox 5.1,
Proxmox network settings two Linux Bridge:
auto vmbr0
iface vmbr0 inet static
address 192.168.88.248
netmask 255.255.255.0
gateway 192.168.88.1
bridge_ports enp3s0
bridge_stp off
bridge_fd 0
auto vmbr1
iface vmbr1 inet static
address 192.168.140.1
netmask 255.255.255.0
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 '192.168.140.0/24' -o enp3s -j MASQUEREAD
88-net physical link enp3s0 to mikrotik.
There is a task in organizing an internal network of 140-net servers, one of them is Ubuntu OpenVpn ,
There are two interfaces on the OpenVpn server, 88,140:
ens18
inet addr:192.168.88.247 Bcast:192.168.88.255 Mask:255.255.255.0
ens19
inet addr:192.168.140.10 Bcast :192.168.140.255 Mask:255.255.255.0
vpn server, configured by the user connects to the network ( 10.8.0.0/24 tun0), I am forwarding two networks, but only 88 is available, and ip 192.168.140.10, other addresses are not available (140-net),
iptables allowed all FORWARD/
Watched tcpdump packets reach the server (140.1), but do not go back
How to properly configure the network on proxmox - ubuntu Openvpn?
I thought about setting up vlan 140 on mikrotik, but in this case, you need to somehow throw the trunk, or use OVZ?

Answer 1

Everything turned out to be simple,
1. On 140-net clients, it was necessary to specify gw Ubuntu (140.10),
2. Nat did not work due to an incorrect FORWARD rule
3. All settings can be removed on the vmbr1 interface

Answer 2

post-up iptables -t nat -A POSTROUTING -s '192.168.140.0/24' -o enp3s -j MASQUEREAD

iptables masquerade )
the first thing I saw