How to properly set up dhcp on ubuntu 18.04?

Question

linux

Hello. Please help me figure out how to set up a DHCP server and get an IP.
Given:
- Virtualbox (latest)
- Ubuntu 18.04 LTS (client)
- Ubuntu Server 18.04 (dhcp)
- virtualbox internal-network
dhcp settings:
dhcpd.conf:

# minimal sample /etc/dhcp/dhcpd.conf
default-lease-time 600;
max-lease-time 7200;

subnet 192.168.33.0 netmask 255.255.255.0 {
 range 192.168.33.20 192.168.33.50;
 option routers 192.168.33.254;
 option domain-name-servers 192.168.33.1, 192.168.33.2;
 option domain-name "ubuntu.local";
}

isc-dhcp-server settings:
INTERFACESv4="enp0s3"
Settings: /etc/netplan
50-cloud-init.yaml:

enp0s3:
    addresses: [192.168.33.20/24, ]
    dhcp4: no
    dhcp6: no
    gateway4: 192.168.33.1
    nameservers:
      addresses: [8.8.8.8, 8.8.4.4]

Ubuntu 18.04 just has Auto IP (DHCP) in the settings,
but does not receive an address. Tell me why, please. If there are ideas.
DHCP Status

Answer 1

default-lease-time 600;
max-lease-time 7200;

subnet 192.168.33.0 netmask 255.255.255.0 {
 range 192.168.33.20 192.168.33.50;
 option routers 192.168.33.254;

Answer 2

dhcpd -t allows you to test the config and find errors.
given that vbox and its internal network are used, but at the same time the config contains an indication of a real device (why is it interesting), then the client will not receive anything there even with a working network.
just in case I will attach part of my config in the place where the networks are described

subnet 10.10.50.0 netmask 255.255.255.0 {
option broadcast-address 10.10.50.255;
ddns-updates on;
ddns-domainname "rectorat.******.ru";
authoritative;
option ntp-servers 172.16.20.100;
option time-servers 172.16.20.100;
option routers 10.10.50.1;
option subnet-mask 255.255.255.0;
option domain-name "rectorat.******.ru";
option domain-name-servers 172.16.11.41;
option nis-domain "rectorat.******.ru";
option local-pac-server " http://wpad.******.ru:80/wpad.dat\000 " ;
pool {
range 10.10.50.10 10.10.50.200;
default-lease-time 504800;
max-lease-time 604800;
} }