OpenWrt-based DHCP/DNS server

Mar 12, 2020

This document describes how to build a simple DHCP/DNS server on top of OpenWrt. We assume you already have a working OpenWrt installation and that you have configured basic networking (/etc/config/network) and the host’s name (/etc/config/system).

The following will configure dnsmasq to provide DHCP (assigning .1–.100), and DNS (e.g., assigning the hostname server.example.com to the computer with MAC address aa:bb:cc:dd:ee:ff). The DNS service will also resolve the local host’s name, as set in /etc/config/system.

config dnsmasq
      option domainneeded '1' 
      option boguspriv '1'
      option filterwin2k '0'
      option localise_queries '1'
      option rebind_protection '1'
      option rebind_localhost '1'
      option local '/example.com/'
      option domain 'example.com'
      option expandhosts '1'
      option nonegcache '0'
      option authoritative '1'
      option readethers '1'
      option leasefile '/tmp/dhcp.leases'
      option resolvfile '/tmp/resolv.conf.auto'
      option server '192.168.1.1' # Upstream DNS.

config dhcp 'lan'
      option interface 'lan'
      option start '1'
      option limit '100'
      option leasetime '12h'
      option dhcpv6 'server'
      option ra 'server'
      list dhcp_option '3,192.168.1.1' # Default gateway.
      list dhcp_option '121,192.168.0.0/16,192.168.1.1' # A static route.

config dhcp 'wan'
      option interface 'wan'
      option ignore '1'

config odhcpd 'odhcpd'
      option maindhcp '0'
      option leasefile '/tmp/hosts/odhcpd'
      option leasetrigger '/usr/sbin/odhcpd-update'

config host
      option name 'server.example.com'
      option ip '192.168.1.101'
      option mac 'aa:bb:cc:dd:ee:ff'