RaspberryPi 3 Retropie OS Wifi using DHCP with DNS and Gateway in different devices

RaspberryPi 3 Retropie OS Wifi using DHCP with DNS and Gateway in different devices

The main three things are these:
1. Inside /etc/network/interfaces:
The wifi interface should be set as dhcp as have the usual settings for using wpa_conf
2. Inside /etc/dhcpcd.conf:
Disable ipv6
Add the the gateway (router) as static routers=...
3. Create a file /etc/sysctl.d/40-ipv6.conf, where you disable ipv6 for all AND for each interface

(more info about ipv6 disabling in https://wiki.archlinux.org/index.php/IPv6#Disable_IPv6)

Example of files mentioned:

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/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

iface eth0 inet manual

allow-hotplug wlan0
auto wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
wireless-power off

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/etc/dhcpcd.conf

# A sample configuration for dhcpcd.
# See dhcpcd.conf(5) for details.

# Allow users of this group to interact with dhcpcd via the control socket.
#controlgroup wheel

# Inform the DHCP server of our hostname for DDNS.
hostname

# Use the hardware address of the interface for the Client ID.
clientid
# or
# Use the same DUID + IAID as set in DHCPv6 for DHCPv4 ClientID as per RFC4361.
#duid

# Persist interface configuration when dhcpcd exits.
persistent

# Rapid commit support.
# Safe to enable by default because it requires the equivalent option set
# on the server to actually work.
option rapid_commit

# A list of options to request from the DHCP server.
option domain_name_servers, domain_name, domain_search, host_name
option classless_static_routes
static routers= # Your router IP here
# Most distributions have NTP support.
option ntp_servers
# Respect the network MTU.
# Some interface drivers reset when changing the MTU so disabled by default.
option interface_mtu

# A ServerID is required by RFC2131.
require dhcp_server_identifier

# Generate Stable Private IPv6 Addresses instead of hardware based ones
#slaac private
noipv6rs
noipv6

# A hook script is provided to lookup the hostname if not set by the DHCP
# server, but it should not be run by default.
# nohook lookup-hostname

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/etc/sysctl.d/40-ipv6.conf 

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.wlan0.disable_ipv6 = 1
net.ipv6.conf.wlan1.disable_ipv6 = 1

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