Connect and bridge internet through ethernet

dhcpd.conf

# https://www.linuxfordevices.com/tutorials/ubuntu/dhcp-server-on-ubuntu

# The default lease time for a client is 10 mins(600 seconds) 
# and the maximum lease time is 2 hrs(7200 seconds).
default-lease-time 600;
max-lease-time 7200;

authoritative;

# This DHCP Server is the official server for the local network. (indicated by authoritative).
subnet 192.168.2.0 netmask 255.255.255.0 {

  # The Server will hand over the IP Address from the range 192.168.1.100 to 192.168.1.200.
  range 192.168.2.100 192.168.2.200;

  # The server will also “advise” the client to use 192.168.1.254 as the default-gateway 
  # and 192.168.1.1 and 192.168.1.2 as its DNS servers.
  option routers 192.168.2.254;
  option broadcast-address 192.168.2.255;
  option domain-name "localdomain.org";
  option domain-name-servers 192.168.2.1, 192.168.2.2;
  option ip-forwarding off;
}

# Run "ip a" you will find - link/ether b0:25:aa:3a:fb:f6
# This will reserve the IP Address 192.168.1.20 for the client with the MAC Address e0:91:53:31:af:ab.
# You may omit the Static IP Configuration part if you want to assign addresses automatically.
host archmachine {
  hardware ethernet b0:25:aa:3a:fb:f6;
  fixed-address 192.168.2.20;
  option host-name "archmachine";
}

interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# Set up interfaces manually, avoiding conflicts with, e.g., network manager
iface eth0 inet manual
iface eth1 inet manual

allow-hotplug eno1
iface eno1 inet static

address 192.168.2.1
netmask 255.255.255.0
network 192.168.2.0
broadcast 192.168.2.255
gateway 192.168.2.1

# Bridge setup
iface br0 inet dhcp
bridge_ports eno1

isc-dhcp-server

# Defaults for isc-dhcp-server (sourced by /etc/init.d/isc-dhcp-server)

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
#DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
#DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf

# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
#DHCPDv4_PID=/var/run/dhcpd.pid
#DHCPDv6_PID=/var/run/dhcpd6.pid

# Additional options to start dhcpd with.
#	Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#	Separate multiple interfaces with spaces, e.g. "eth0 eth1".
INTERFACESv4="eno1"
INTERFACESv6=""

sudo brctl addbr br0

sudo ifconfig eno1 192.168.2.20

# 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;

# The default lease time for a client is 10 mins(600 seconds) 
# and the maximum lease time is 2 hrs(7200 seconds).
# default-lease-time 600;
# max-lease-time 7200;

# The ddns-updates-style parameter controls whether or not the server will
# attempt to do a DNS update when a lease is confirmed. We default to the
# behavior of the version 2 packages ('none', since DHCP v2 didn't
# have support for DDNS.)
# ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
#log-facility local7;

# No service will be given on this subnet, but declaring it helps the 
# DHCP server to understand the network topology.

#subnet 10.152.187.0 netmask 255.255.255.0 {
#}

# This is a very basic subnet declaration.

#subnet 10.254.239.0 netmask 255.255.255.224 {
#  range 10.254.239.10 10.254.239.20;
#  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
#}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

#subnet 10.254.239.32 netmask 255.255.255.224 {
#  range dynamic-bootp 10.254.239.40 10.254.239.60;
#  option broadcast-address 10.254.239.31;
#  option routers rtr-239-32-1.example.org;
#}

# A slightly different configuration for an internal subnet.
#subnet 10.5.5.0 netmask 255.255.255.224 {
#  range 10.5.5.26 10.5.5.30;
#  option domain-name-servers ns1.internal.example.org;
#  option domain-name "internal.example.org";
#  option routers 10.5.5.1;
#  option broadcast-address 10.5.5.31;
#  default-lease-time 600;
#  max-lease-time 7200;
#}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

#host passacaglia {
#  hardware ethernet 0:0:c0:5d:bd:95;
#  filename "vmunix.passacaglia";
#  server-name "toccata.example.com";
#}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
#host fantasia {
#  hardware ethernet 08:00:07:26:c0:a5;
#  fixed-address fantasia.example.com;
#}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

#class "foo" {
#  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
#}

#shared-network 224-29 {
#  subnet 10.17.224.0 netmask 255.255.255.0 {
#    option routers rtr-224.example.org;
#  }
#  subnet 10.0.29.0 netmask 255.255.255.0 {
#    option routers rtr-29.example.org;
#  }
#  pool {
#    allow members of "foo";
#    range 10.17.224.10 10.17.224.250;
#  }
#  pool {
#    deny members of "foo";
#    range 10.0.29.10 10.0.29.230;
#  }
#}

# https://www.linuxfordevices.com/tutorials/ubuntu/dhcp-server-on-ubuntu

# The default lease time for a client is 10 mins(600 seconds) 
# and the maximum lease time is 2 hrs(7200 seconds).
default-lease-time 600;
max-lease-time 7200;

authoritative;

# This DHCP Server is the official server for the local network. (indicated by authoritative).
subnet 192.168.2.0 netmask 255.255.255.0 {
 
  # The Server will hand over the IP Address from the range 192.168.1.100 to 192.168.1.200.
  range 192.168.2.100 192.168.2.200;
  # The server will also “advise” the client to use 192.168.1.254 as the default-gateway 
  # and 192.168.1.1 and 192.168.1.2 as its DNS servers.
  option routers 192.168.2.201;
  option broadcast-address 192.168.2.255;
  option domain-name "localdomain";
  option domain-name-servers 192.168.2.1, 192.168.2.2, 1.1.1.1, 8.8.8.8;
  option ip-forwarding on;

  # # Run "ip a" you will find - link/ether b0:25:aa:3a:fb:f6
  # # This will reserve the IP Address 192.168.1.20 for the client with the MAC Address e0:91:53:31:af:ab.
  # # You may omit the Static IP Configuration part if you want to assign addresses automatically.
  host archmachine {
    hardware ethernet b0:25:aa:3a:fb:f6;
    fixed-address 192.168.2.22;
  }

  # 1. You have TWO subnets with router in between and want to have ONE DHCP server responsible for IP address assignement. In this case you likely should have a look at dhcprelay (which is also a part of isc-dhcp) or so called "ip helper" or "dhcp helper" on a switch / router.
  # 2. You want two SHARE single physical network segment between TWO subnets. In this case you have to put both subnets in shared-network statement.

  host router {
    hardware ethernet f4:6d:04:bf:02:27;
    fixed-address 192.168.2.1;
  }
}