# vi /etc/dhcpcd.conf (追記)
interface eth0

 static ip_address=192.168.1.7/24
 static routers=192.168.1.1
 static domain_name_servers=192.168.1.1

もしアドレスを固定にするならば・・・
http://swiftlife.hatenablog.jp/entry/2016/01/10/170249

/etc/resolv.conf を変更する。
nameserver (DNSサーバのIPアドレス)
$ sudo /etc/init.d/networking reload (設定反映)

# wpa_passphrase BBUser870201 XXXXXXXXXXXXXXXXXXX
# sudo vi /etc/wpa_supplicant/wpa_supplicant.conf
=|BOX|
network={

      ssid="BBUser870201"
      psk=xxxxxxxxxxx....................xxxxx
      proto=RSN
      key_mgmt=WPA-PSK
      pairwise=CCMP
      auth_alg=OPEN

}

# ifconfig wlan0 down
# ifconfig wlan0 up
# ifconfig wlan0

# vi /etc/network/interfaces
=|BOX|
# auto wlan0 ← 要否不明
allow-hotplug wlan0
iface wlan0 inet dhcp ←manuaでないとアドレスを取れないかも
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

# vi /etc/dhcpcd.conf
=|BOX|
interface wlan0
static ip_address=192.168.1.62/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.1

# vi /etc/modprobe.d/8192cu.conf
=|BOX|
# Disable power saving
options 8192cu rtw_power_mgnt=0 rtw_enusbss=1 rtw_ips_mode=1

*DHCPから取得

# vi /etc/dhcp/dhclient.conf
=|BOX|

  send dhcp-client-identifier=hardware;  (こちらは必須・スペースなし)

||=
# vi /etc/dhcpcd.conf
=|BOX|

  send dhcp-client-identifier = hardware;  (こちらは必須ではないみたい)
  interface eth0
  #static ip_address=192.168.1.52/24
  #static routers=192.168.1.1
  #static domain_name_servers=192.168.1.1

  interface wlan0
  #static ip_address=192.168.1.62/24
  #static routers=192.168.1.1
  #static domain_name_servers=192.168.1.1

||=

# vi /etc/network/interfaces
=|BOX|

  #iface eth0 inet manual
  iface eth0 inet dhcp

  allow-hotplug wlan0
  #iface wlan0 inet manual
  iface wlan0 inet dhcp

||=

hostapdを使わないならこの設定
# vi /etc/network/infterfaces
=|BOX|
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp

wpa-ssid [SSID]
wpa-psk [PWD]

(wpa_supplicant.confに書いても良い)

# vi /etc/network/interfaces
=|BOX|
# wlan0
iface wlan0 inet static
address 192.168.20.1
netmask 255.255.255.0
gateway 192.168.20.1

# eth1
iface eth1 inet static
address 192.168.21.1
netmask 255.255.255.0
gateway 192.168.21.1