Installing and Configuring a DHCP Server

This guide walks you through setting up isc-dhcp-server on your xCore board.

Why Set Up a DHCP Server?

The xCore board serves as the central hub in an internal network used by your robot. The xCore includes a microcontroller (STM32) which talks directly with the Linux system. To enable this, we create a private network on eth0 with a static IP and assign dynamic IPs to connected devices using DHCP. The STM32 will acquire an IP address automatically.

Step 1: Set Static IP on `eth0`

We will assign a static IP 172.16.78.1 to eth0. You can do this using the built-in network configuration utility:

sudo nmtui

Select Edit a connection
Choose your Wired connection
Set IPv4 Configuration to Manual
Add:
- Address: 172.16.78.1
- Netmask: 255.255.255.0
- Gateway: leave blank
Save and Activate the connection

💡 You may also use nmcli instead:

sudo nmcli con mod "Wired connection 1" ipv4.method manual ipv4.addresses 172.16.78.1/24
sudo nmcli con up "Wired connection 1"

Verify the result by running ip -4 address show dev eth0. The expected output should be:

robot@robot:~ $ ip -4 address show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    inet 172.16.78.1/24 brd 172.16.78.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever

Step 2: Install the DHCP Server

sudo apt-get update
sudo apt-get install isc-dhcp-server -y

Step 3: Configure DHCP Server

Edit default interface

Open /etc/default/isc-dhcp-server:

sudo nano /etc/default/isc-dhcp-server

Find and modify this line:

INTERFACESv4="eth0"

Save the configuration by pressing CTRL+O, ENTER. Then exit nano by pressing CTRL+X.

Add DHCP configuration

Edit the main DHCP config file:

sudo nano /etc/dhcp/dhcpd.conf

Replace the config with the following:

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

subnet 172.16.78.0 netmask 255.255.255.0 {
  interface eth0;
  range 172.16.78.150 172.16.78.200;
  option routers 172.16.78.1;
  option domain-name-servers 172.16.78.1;
  option domain-name "robot.local";
}

Step 4: Start the DHCP Server

sudo systemctl start isc-dhcp-server

Enable it at boot:

sudo systemctl enable isc-dhcp-server

Verification

Run:

sudo systemctl status isc-dhcp-server

Make sure the output includes active (running).

Try to ping your STM32: Get the assigned IP by running cat /var/lib/dhcp/dhcpd.leases

Example output:

robot@robot:~ $ cat /var/lib/dhcp/dhcpd.leases
# The format of this file is documented in the dhcpd.leases(5) manual page.
# This lease file was written by isc-dhcp-4.4.3-P1

# authoring-byte-order entry is generated, DO NOT DELETE
authoring-byte-order little-endian;

server-duid "\000\001\000\001/\244\342\375,\317gJ\305\345";

lease 172.16.78.150 {
  starts 3 2025/04/30 13:33:05;
  ends 3 2025/04/30 13:43:05;
  cltt 3 2025/04/30 13:33:05;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet d8:47:8f:91:b9:6c;
}

Then you should be able to ping the STM32:

robot@robot:~ $ ping 172.16.78.150
PING 172.16.78.150 (172.16.78.150) 56(84) bytes of data.
64 bytes from 172.16.78.150: icmp_seq=1 ttl=255 time=0.354 ms

Last modified April 30, 2025: Added DHCP server tutorial (49f3826)