Lost connection to remote computer after starting the DHCP server (Ubuntu 20.04.1)

I have a laptop in the university network with both WiFi and Ethernet.

I tried to start the DHCP server on its Ethernet port according to this tutorial and lost connectivity after DHCP server started. At the moment of set-up, the laptop was connected to the university network with WiFi, was reachable from the network and I used ssh to configure it.

What was done:

# installing the isc-dhcp-server
sudo apt install isc-dhcp-server -y
# configuring via editing the /etc/dhcp/dhcpd.conf
sudo nano /etc/dhcp/dhcpd.conf

In file /etc/dhcp/dhcpd.conf I:

1. uncommented line authoritative;
2. added following in the end:

subnet 10.42.15.0 netmask 255.255.255.0 {
    interface enp0s25;

    option routers 10.42.15.1;
    option domain-name-servers 10.42.15.1;
    range 10.42.15.10 10.42.15.255;
}

Where enp0s25 is Ethernet interface obtained using the ip addr, while for WiFi it is wlo1.

After that, I started the dhcp server as:

sudo systemctl start isc-dhcp-server

And the same time I lost connection to the laptop.

What I’ve done wrong and what should be done differently to prevent such behaviour?

Thank you!