Howto dhcp server: Difference between revisions

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first we need to configure our network interfaces for the server:
* '''eth0''' interface connected to the internet
* '''eth1''' interface connected to lan
make sure you have network-manager installed:
yum install networkmanager -y
start and enable networkmanager:
systemctl start NetworkManager
systemctl enable NetworkManager
erase default network profiles:
nmcli con del eth0
nmcli con del eth1
nmcli con del Wired\ connection\ 1
nmcli con del Wired\ connection\ 2
configure network interfaces nmcli:
nmcli con add con-name eth0 ipv4.method manual type ethernet ifname eth0 ipv4.addresses 192.168.75.254/24 ipv4.gateway 192.168.75.1 ipv4.dns 4.2.2.1,4.2.2.2 autoconnect yes
nmcli con add con-name eth1 ipv4.method manual type ethernet ifname eth1 ipv4.addresses 192.168.33.1/24  autoconnect yes
= configuring dhcp service =
first we install the required package:
first we install the required package:
  yum install dhcp -y
  yum install dhcp -y
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                 option broadcast-address '''192.168.33.255''';
                 option broadcast-address '''192.168.33.255''';
                 option routers '''192.168.33.1''';
                 option routers '''192.168.33.1''';
                 option domain-name "'''cdqgroup.com'''";
                 option domain-name "'''example.com'''";
                 option domain-name-servers '''192.168.33.1''';
                 option domain-name-servers '''192.168.33.1''';
                 default-lease-time 600;
                 default-lease-time 600;
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   }
   }
  }
  }
in our server we need configure our network interfaces:
if you want to assign specific ip address to a client add the following:
host linuxwebserver {
        hardware ethernet 00:40:F4:A8:60:5E;
        fixed-address 192.168.3.3;
}
copy and modify dhcpd.service to specify dhcp server network interface:
cp /usr/lib/systemd/system/dhcpd.service /etc/systemd/system/
edit ExecStart command on /etc/systemd/system/dhcpd.service and add your network interface:
ExecStart=/usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid eth1
then reload systemd and start the service:
systemctl --system daemon-reload
systemctl restart dhcpd.service
make sure to add dhcpd service to start at boot:
systemctl enable dhcpd
 
= firewalld rules =
enable ip forwarding:
nano /etc/sysctl.d/99-sysctl.conf
add the following line at the end of this file:
net.ipv4.ip_forward = 1
apply changes:
sysctl -p /etc/sysctl.d/99-sysctl.conf
please install the following package:
yum -y install iptables-services
flush any iptables rule on system:
iptables -F -v
iptables -F -v -t nat
network interfaces configuration:
* '''eth0''' interface connected to the internet
* '''eth0''' interface connected to the internet
* '''eth1''' interface connected to lan
* '''eth1''' interface connected to lan
make sure you have network-manager installed:
add the following rules to forward the traffic from internet to lan and masquerade out going traffic:
yum install networkmanager -y
  iptables -t nat -A POSTROUTING -o '''eth0''' -j MASQUERADE
start and enable networkmanager:
  iptables -A FORWARD -i '''eth1''' -j ACCEPT
systemctl start NetworkManager
safe this rules and configure iptables to start at boot:
systemctl enable NetworkManager
  service iptables save
erase default network profiles:
systemctl enable iptables
nmcli con del eth0
nmcli con del eth1
nmcli con del Wired\ connection\ 1
nmcli con del Wired\ connection\ 2
configure network interfaces nmcli:
nmcli con add con-name eth0 ipv4.method manual type ethernet ifname eth0 ipv4.addresses 192.168.75.254/24 ipv4.gateway 192.168.75.1 ipv4.dns 4.2.2.1,4.2.2.2 autoconnect yes
nmcli con add con-name eth1 ipv4.method manual type ethernet ifname eth1 ipv4.addresses 192.168.33.1/24  autoconnect yes
Para reservar un IP en especifico a una maquina hacemos lo a traves de hardware address siguiente:
host lab3 {
        hardware ethernet 00:40:F4:A8:60:5E;
        fixed-address 192.168.2.3;
}
Debemos asignar la interface que estara repartiendo IP, editamos el archivo '''/etc/sysconfig/dhcpd''':
DHCPDARGS=eth0
Luego de esto subimos el servicio de dhcpd con el siguiente comando
service dhcpd start
Se supone que si tenemos dos interface una de ellas se conecta al internet y otra reparte IP con el servidor DHCP que acabamos de configurar, y lo que deseamos es compartir este internet que viene de la otra interface con la red que esta tomando IP de nuestro servidor DHCP, utilizamos los siguientes comandos para establecer reglas con IPTABLES que nos permitan lograrlo:
  iptables --table nat --append POSTROUTING --out-interface '''INTERNET''' -j MASQUERADE
  iptables --append FORWARD --in-interface '''NETWORK''' -j ACCEPT
  echo 1 > /proc/sys/net/ipv4/ip_forward
'''INTERNET''' = eth0
'''NETWORK''' = eth1

Latest revision as of 17:50, 2 August 2020

first we need to configure our network interfaces for the server:

  • eth0 interface connected to the internet
  • eth1 interface connected to lan

make sure you have network-manager installed: 

yum install networkmanager -y

start and enable networkmanager: 

systemctl start NetworkManager
systemctl enable NetworkManager

erase default network profiles: 

nmcli con del eth0
nmcli con del eth1
nmcli con del Wired\ connection\ 1
nmcli con del Wired\ connection\ 2

configure network interfaces nmcli: 

nmcli con add con-name eth0 ipv4.method manual type ethernet ifname eth0 ipv4.addresses 192.168.75.254/24 ipv4.gateway 192.168.75.1 ipv4.dns 4.2.2.1,4.2.2.2 autoconnect yes
nmcli con add con-name eth1 ipv4.method manual type ethernet ifname eth1 ipv4.addresses 192.168.33.1/24  autoconnect yes

configuring dhcp service

first we install the required package: 

yum install dhcp -y

edit the dhcp server configuration file at /etc/dhcp/dhcpd.conf: 

server-identifier server;
ddns-update-style ad-hoc;
shared-network DHCP {
      option subnet-mask 255.255.255.0;

        subnet 192.168.33.0 netmask 255.255.255.0 {
                range 192.168.33.100 192.168.33.150;
                option broadcast-address 192.168.33.255;
                option routers 192.168.33.1;
                option domain-name "example.com";
                option domain-name-servers 192.168.33.1;
                default-lease-time 600;
                max-lease-time 7200;
 }
}

if you want to assign specific ip address to a client add the following: 

host linuxwebserver {
        hardware ethernet 00:40:F4:A8:60:5E;
        fixed-address 192.168.3.3;
}

copy and modify dhcpd.service to specify dhcp server network interface: 

cp /usr/lib/systemd/system/dhcpd.service /etc/systemd/system/

edit ExecStart command on /etc/systemd/system/dhcpd.service and add your network interface: 

ExecStart=/usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid eth1

then reload systemd and start the service: 

systemctl --system daemon-reload
systemctl restart dhcpd.service

make sure to add dhcpd service to start at boot: 

systemctl enable dhcpd

firewalld rules

enable ip forwarding: 

nano /etc/sysctl.d/99-sysctl.conf

add the following line at the end of this file: 

net.ipv4.ip_forward = 1

apply changes: 

sysctl -p /etc/sysctl.d/99-sysctl.conf

please install the following package: 

yum -y install iptables-services

flush any iptables rule on system: 

iptables -F -v
iptables -F -v -t nat

network interfaces configuration:

  • eth0 interface connected to the internet
  • eth1 interface connected to lan

add the following rules to forward the traffic from internet to lan and masquerade out going traffic: 

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A FORWARD -i eth1 -j ACCEPT

safe this rules and configure iptables to start at boot: 

service iptables save
systemctl enable iptables
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