Problema ao fazer a ponte funcionar quando configurada com um script

Question

Estou tentando configurar uma ponte, basicamente transformando minha máquina em um comutador.

Estou executando um servidor dhcp na mesma máquina com INTERFACES='br0' como configuração de interface.

/etc/network/interfaces é assim:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
auto eth1
iface eth1 inet manual
auto wlan0
iface wlan0 inet manual

auto br0
iface br0 inet static
    bridge_ports eth0 eth1 wlan0
    address 10.1.36.10
    netmask 255.255.255.0
    network 10.1.36.0
    broadcast 10.1.36.255

Quando configurei isso manualmente, tudo funcionou bem.

Escrevi então um script bash para configurar isso, já que preciso configurar várias máquinas da mesma maneira:

echo "Setting up Static IP..."
if [ $(ifconfig -a | sed 's/[ \t].*//;/^\(lo\|\)$/d' | wc -l) -gt 1 ]
then
   BRIDGE_PORTS=""
   for i in $(ifconfig -a | sed 's/[ \t].*//;/^\(lo\|\)$/d'); do
       sudo echo "auto $i" | sudo tee -a  /etc/network/interfaces
       sudo echo "iface $i inet manual" | sudo tee -a  /etc/network/interfaces
       BRIDGE_PORTS="$BRIDGE_PORTS $i "
   done
   sudo echo "auto br0" | sudo tee -a  /etc/network/interfaces
   sudo echo "iface br0 inet static" | sudo tee -a  /etc/network/interfaces
   sudo echo "bridge_ports $BRIDGE_PORTS" | sudo tee -a  /etc/network/interfaces
   sudo echo "address $STATIC_IP" | sudo tee -a  /etc/network/interfaces
   sudo echo "netmask 255.255.255.0" | sudo tee -a  /etc/network/interfaces
   sudo echo "network $NETWORK_IP" | sudo tee -a  /etc/network/interfaces
   sudo echo "broadcast $BROADCAST_IP" | sudo tee -a  /etc/network/interfaces
   DHCP_INTERFACE="br0"
else
   sudo echo "auto eth0" | sudo tee -a  /etc/network/interfaces
   sudo echo "iface eth0 inet static" | sudo tee -a  /etc/network/interfaces
   sudo echo "address $STATIC_IP" | sudo tee -a  /etc/network/interfaces
   sudo echo "netmask 255.255.255.0" | sudo tee -a  /etc/network/interfaces
   sudo echo "network $NETWORK_IP" | sudo tee -a  /etc/network/interfaces
   sudo echo "broadcast $BROADCAST_IP" | sudo tee -a  /etc/network/interfaces
   DHCP_INTERFACE="eth0"
fi

Eu não sei por que, mas a bridge não inclui as interfaces eth0 ou eth1 quando configuro com o script.

Quando executo ip addr , obtenho isto:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
   valid_lft forever preferred_lft forever
inet6 ::1/128 scope host 
   valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default      qlen 1000
link/ether 78:d0:04:20:b9:6c brd ff:ff:ff:ff:ff:ff
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
link/ether 78:d0:04:20:b9:6d brd ff:ff:ff:ff:ff:ff
4: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP group default qlen 1000
link/ether c4:d9:87:8e:72:f9 brd ff:ff:ff:ff:ff:ff
inet6 fe80::c6d9:87ff:fe8e:72f9/64 scope link 
   valid_lft forever preferred_lft forever
5: mon.wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UNKNOWN group default qlen 1000
link/ieee802.11/radiotap c4:d9:87:8e:72:f9 brd ff:ff:ff:ff:ff:ff
6: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
link/ether c4:d9:87:8e:72:f9 brd ff:ff:ff:ff:ff:ff
inet 10.1.36.10/24 brd 10.1.36.255 scope global br0
   valid_lft forever preferred_lft forever
inet6 fe80::c6d9:87ff:fe8e:72f9/64 scope link 
   valid_lft forever preferred_lft forever

A eth0 e eth1 não têm br0 como seu mestre! Por que isso?