Adding more network on Proxmox

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto vmbr0
iface vmbr0 inet static
        address 192.168.123.7
        netmask 255.255.255.0
        network 192.168.123.0
        broadcast 192.168.123.255
        gateway 192.168.123.254
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0

auto vmbr1
iface vmbr1 inet static
        address 192.168.1.1
        netmask 255.255.255.0
        bridge_ports none
        bridge_stp off
        bridge_fd 0

#================= standar konfig =================
#post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -t nat -A POSTROUTING -s '192.168.1.0/24' -o vmbr0 -j MASQUERADE
post-up iptables -A FORWARD -s '192.168.1.0/24' -o vmbr0 -j ACCEPT
post-up iptables -A FORWARD -d '192.168.1.0/24' -m state --state ESTABLISHED,RELATED -i vmbr0 -j ACCEPT