Wifiで受信したネットワークにLANで接続する機器も自動IP割り振りするような感じ
記載内容は参考サイトを自分用メモにしたのと、最後の箇所は、動作しなかったを解消調べ

1. /etc/network/interfacesの編集

1.1.追加内容

auto lo
iface lo inet loopback
 
auto eth0
allow-hotplug eth0
iface eth0 inet manual
 
auto wlan1
allow-hotplug wlan1
iface wlan1 inet dhcp
        wpa-conf  /etc/wpa_supplicant/wpa_supplicant.conf

1.2.全体ソース

/etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback
 
auto eth0
allow-hotplug eth0
iface eth0 inet manual
 
auto wlan1
allow-hotplug wlan1
iface wlan1 inet dhcp
        wpa-conf  /etc/wpa_supplicant/wpa_supplicant.conf

2./etc/wpa_supplicant/wpa_supplicant.confの編集

Wifi接続情報を保持を複数を記述できるようです

2.1.追加内容

network={
	ssid="SSID"
	psk="パスワード"
	key_mgmt=WPA-PSK
	scan_ssid=1
}

2.2.全体ソース

/etc/wpa_supplicant/wpa_supplicant.conf

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

network={
	ssid="SSID"
	psk="パスワード"
	key_mgmt=WPA-PSK
	scan_ssid=1
}

3./etc/rc.localでIP forwardの設定

3.1.追加内容

echo 1 > /proc/sys/net/ipv4/ip_forward

3.2.全体ソース

/etc/rc.local

# !/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

echo 1 > /proc/sys/net/ipv4/ip_forward

exit 0

4.DHCPリレーエージェントのインストールと設定の編集

4.1.インストール

sudo apt-get install dhcp-helper

4.2./etc/default/dhcp-helperでDHCPリレーエージェントの設定を編集

4.2.1.追加内容

DHCPHELPER_OPTS="-b wlan1"

4.2.2.全体ソース

/etc/default/dhcp-helper

# Option flags used to start dhcp-helper.
#
# You will need at least "-s <DHCP server>" or
# "-b <interface> so that dhcp-helper knows where 
# to relay DHCP requests. 
#
# See "man 8 dhcp-helper" for more details.  

DHCPHELPER_OPTS="-b wlan1"

5.Proxy ARPブリッジのインストールと設定編集

5.1.インストール

sudo apt-get install parprouted

5.2./etc/rc.localでProxyでARPブリッジ設定を編集

5.2.1.追加内容

ip addr add 192.168.1.203 dev eth0
parprouted wlan1 eth0

5.2.2.全体ソース

/etc/rc.local

# !/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi

echo 1 > /proc/sys/net/ipv4/ip_forward
ip addr add 192.168.1.203 dev eth0
parprouted wlan1 eth0

exit 0

参考サイトはここまでで、動作しなかったので、追記した箇所は以下

6.動作しないを解消

6.1./etc/network/interfacesを編集

6.1.1.追記内容

post-up /sbin/ip addr add $(/sbin/ip addr show wlan1 | perl -wne 'm|^\s+inet (.*)/| && print $1')/32 dev eth0
  post-up /sbin/ifup eth0
  post-up /usr/sbin/parprouted wlan1 eth0
  post-up /etc/init.d/dhcp-helper start
  post-down /usr/bin/killall /usr/sbin/parprouted
  post-down /etc/init.d/dhcp-helper stop
  post-down /sbin/ifdown eth0

6.1.2.全体ソースコード

/etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback
 
auto eth0
allow-hotplug eth0
iface eth0 inet manual
 
auto wlan1
allow-hotplug wlan1
iface wlan1 inet dhcp
        wpa-conf  /etc/wpa_supplicant/wpa_supplicant.conf

post-up /sbin/ip addr add $(/sbin/ip addr show wlan1 | perl -wne 'm|^\s+inet (.*)/| && print $1')/32 dev eth0
  post-up /sbin/ifup eth0
  post-up /usr/sbin/parprouted wlan1 eth0
  post-up /etc/init.d/dhcp-helper start
  post-down /usr/bin/killall /usr/sbin/parprouted
  post-down /etc/init.d/dhcp-helper stop
  post-down /sbin/ifdown eth0

7.本体のWifiをOFF

OFF

sudo iwconfig wlan0 txpower off

ON

sudo iwconfig wlan0 txpower auto

参考サイト

Raspberry Pi3を無線LANコンバータにする
http://rufas.manyoldmoon.com/blog/1604

Bridging Wireless & Ethernet networks with a Raspberry Pi
https://www.yergler.net/tag/network/