참고 출처: https://www.server-world.info/en/note?os=CentOS_7&p=dhcp

1. Enable IPv4 packet forwarding.

Add the following to /etc/sysctl.conf: net.ipv4.ip_forward = 1

Apply the sysctl settings: sysctl -p

2. Add direct rules to firewalld. Add the --permanent option to keep these rules across restarts.

firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -o eth_ext -j MASQUERADE

firewall-cmd --direct --add-rule ipv4 filter FORWARD 0 -i eth_int -o eth_ext -j ACCEPT

firewall-cmd --direct --add-rule ipv4 filter FORWARD 0 -i eth_ext -o eth_int -m state --state RELATED,ESTABLISHED -j ACCEPT

3. DHCP서버 설정하기

# yum -y install dhcp

# vi /etc/dhcp/dhcpd.conf

#************************ dhcpd.conf내용 시작

#************************ internal존의 이더넷 IP(gateway IP)가 192.168.1.1일 경우의 샘플

# default lease time

default-lease-time 600;

# max lease time

max-lease-time 7200;

# this DHCP server to be declared valid

authoritative;

# specify network address and subnet mask

subnet 192.168.1.0 netmask 255.255.255.0 {

    # specify the range of lease IP address

    range dynamic-bootp 192.168.1.2 192.168.1.254;

    # specify broadcast address

    option broadcast-address 192.168.1.255;

    # specify default gateway

    option routers 192.168.1.1;

}

#************************ dhcpd.conf내용 끝 

4. DHCP서버 데몬시작하고 자동실행 가능하게 하기

# systemctl start dhcpd

#systemctl enable dhcpd

5. 방화벽 dhcp서비스 추가하고 적용하기

#firewall-cmd --add-service=dhcp --zone=internal --permanent

#firewall-cmd --reload