muliple ssids

interfaces

# put the following content in /etc/network/interfaces
auto lo
iface lo inet loopback

iface eth0 inet dhcp

auto wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf

iface default inet dhcp

wpa_supplicant.conf

# put this content in /etc/wpa_supplicant/wpa_supplicant.conf

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
	ssid="mon-ssid"
	psk="ma-cle-secrete"
	id_str="home"
}

network={
	ssid="eduroam"
	proto=WPA
	key_mgmt=WPA-EAP
	eap=TTLS
	phase2="auth=PAP"
	pairwise=TKIP
	anonymous_identity="anonymous@univ-reims.fr"
	identity="login"
	password="password"
	id_str="URCA"
}