On your proxmox server edit /etc/interfaces and add a vmbr1 interface like so
load kernel module dummy. modprobe dummy
auto lo
iface lo inet loopback
auto vmbr0
iface vmbr0 inet static
address 167.114.101.88
netmask 255.255.255.0
gateway 167.114.101.254
broadcast 167.114.101.255
network 167.114.101.0
bridge_ports eth0
bridge_stp off
bridge_fd 0
# Internal Network
auto vmbr1
iface vmbr1 inet static
address 10.0.1.1/23
bridge_ports dummy0
bridge_stp off
bridge_fd 0
post-up /sbin/iptables -t nat -A POSTROUTING -o vmbr0 -j MASQUERADE
pre-down /sbin/iptables -t nat -D POSTROUTING -o vmbr0 -j MASQUERADE
Bring up the new vmbr1 interface
ifdown vmbr1 && ifup vmbr1
Then enable ip forwarding in /etc/sysctl.conf
net.ipv4.ip_forward=1
Load the new values
sysctl -p /etc/sysctl.conf
On your vm configure networking like so
auto eth0
iface eth0 inet static
address 10.0.1.100
netmask 255.255.254.0
gateway 10.0.1.1
