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How to create a hotspot on Linux 🐧?

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Overview

Hotspot

What is a hotspot?

From wikipedia A hotspot is a physical location where people may obtain Internet access, typically using Wi-Fi technology, via a wireless local-area network (WLAN) using a router connected to an Internet service provider. Public hotspots may be created by a business for use by customers, such as coffee shops or hotels.

How to create it?

We can have many methods to create a hotspot WIFI depending of Linux 🐧 used. In this tutorial, we will try to use a general method.

Requirements

hostapd

hostapd is a user space daemon software enabling a network interface card to act as an Access Point (AP) and authentication server.

Capabilities of Hostapd (What it can do)

  • Create an AP;
  • Create multiple APs on the same card (if the card supports it, usually up to 8);

dhcpd

dhcpd is a DHCP server program that operates as a daemon on a server to provide Dynamic Host Configuration Protocol (DHCP) service to a network

A WiFi card with AP mode support is needed:

To verify it, run the command below.

iw list | grep "Supported interface modes" -A 8

We will have an output like:

Supported interface modes:

  • IBSS
  • managed
  • AP
  • AP/VLAN
  • WDS
  • monitor
  • P2P-client
  • P2P-GO

Installation of hostapd

We need to download and compile the hostapd source.

wget -t 3 https://w1.fi/cgit/hostap/snapshot/hostap_2_10.tar.gz
tar -xf hostap_2_10.tar.gz
cd hostap_2_10/hostapd
cp defconfig .config
make
make install

Sample configuration We need to config our hostapd.

802.11b/g/n with WPA2-PSK and CCMP

A simple but secure AP with maximal compatibility for current hardware:

Identify our wireless interface

FILE: /etc/hostapd/hostapd.conf We need to identify our wireless interface.

iw dev | grep "Interface"

In this example, we will use wlan0 as our wireless interface. But you should replace it by your own.

# the interface used by the AP
interface=wlan0
# "g" simply means 2.4GHz band
hw_mode=g
# the channel to use
channel=10
# limit the frequencies used to those allowed in the country
ieee80211d=1
# the country code
country_code=FR
# 802.11n support
ieee80211n=1
# QoS support, also required for full speed on 802.11n/ac/ax
wmm_enabled=1

# the name of the AP
ssid=somename
# 1=wpa, 2=wep, 3=both
auth_algs=1
# WPA2 only
wpa=2
wpa_key_mgmt=WPA-PSK
rsn_pairwise=CCMP
wpa_passphrase=somepassword

Start our AP

Before it, we need to disable our wireless interface as client. We suppose that you will use wpa_supplicant.

kill $pidof(wpa_supplicant)

An AP's interface really is just an Ethernet interface, then we need to config the AP's IP and network.

ip addr add 192.168.237.1 dev wlan0

We can start now our AP.

hostapd /etc/hostapd/hostapd.conf

At this point, our AP is functional. But the client should config his IP address manually to communicate in the network.

Installation of a DHCP Server

A DHCP server will permit to assign automatically an IP address to each client of our network.

We will download and compile the dhcpd source.

wget -t 3 https://github.com/isc-projects/dhcp/archive/refs/tags/v4_4_2b1_f2.tar.gz
tar -xf v4_4_2b1_f2.tar.gz
cd dhcp-4_4_2b1_f2
./configure --prefix /usr
make
make install

Sample configuration

We need to config our dhcpd.

FILE: /etc/dhcpd/dhcpd.conf

# -------------------------
# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "example.org";
# option domain-name-servers ns1.example.org, ns2.example.org;

default-lease-time 1800;
max-lease-time 7200;

# We're going to be authoritative for the network we've
# just created.

authoritative;

# No service will be given on this subnet, but we're telling
# the DHCP server about it so it understands it's there and
# not to hand out leases for it.

# subnet 10.14.8.195 netmask 255.255.255.0 {
# }

# But we do want to hand out leases for the 192.168.237.0/24
# network for purposes of this test..

subnet 192.168.237.0 netmask 255.255.255.0 {
    range 192.168.237.100 192.168.237.150;
    # option domain-name-servers      10.21.27.253;
    option routers 192.168.237.1;
}
# -------------------------

Start our DHCP server

dhcpd -f -cf /etc/hostapd/hostapd.conf

Now, if we try to connect a client to our AP, this client will receive automatically an IP address.

Source:

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