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content/blog/pidhcp.md

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+---
+title: "DHCP for Raspberry Pi"
+date: 2021-02-15T22:46:21-05:00
+draft: false
+tags: []
+---
+
+Recently I ran across the use case where I needed a Raspberry Pi to be connected to the Internet via a WiFI connection, while also providing DHCP leases through an Ethernet connection. I couldn't find a great way to achieve this with `dhcpcd` so instead I grabbed a tool that I'm more familiar with `dnsmasq`. 
+
+Before we begin, we need to setup a static IP for the Ethernet interface (`eth0`). Since the Ethernet interface will not be connected to the Internet, there's no need to worry about a lot of the usual fields.
+
+In `/etc/dhcpcd.conf`
+
+```
+interface eth0
+fallback nodhcp
+
+profile nodhcp
+static ip_address=192.168.2.1/24
+```
+
+Below is the config for `dnsmasq` which lives in `/etc/dnsmasq.conf`. It essentially tells it to only serve DHCP leases on the Ethernet connection of the Raspberry Pi. The addresses it'll lease out according to the config below is between 192.168.0.50-192.168.0.150 and is leased for 12 hours.
+
+```
+# Configuration file for dnsmasq.
+#
+# Format is one option per line, legal options are the same
+# as the long options legal on the command line. See
+# "/usr/sbin/dnsmasq --help" or "man 8 dnsmasq" for details.
+
+# Listen on this specific port instead of the standard DNS port
+# (53). Setting this to zero completely disables DNS function,
+# leaving only DHCP and/or TFTP.
+port=0
+
+# If you want dnsmasq to listen for DHCP and DNS requests only on
+# specified interfaces (and the loopback) give the name of the
+# interface (eg eth0) here.
+# Repeat the line for more than one interface.
+interface=eth0
+# Or you can specify which interface _not_ to listen on
+#except-interface=
+# Or which to listen on by address (remember to include 127.0.0.1 if
+# you use this.)
+#listen-address=
+
+# Uncomment this to enable the integrated DHCP server, you need
+# to supply the range of addresses available for lease and optionally
+# a lease time. If you have more than one network, you will need to
+# repeat this for each network on which you want to supply DHCP
+# service.
+dhcp-range=192.168.0.50,192.168.0.150,12h
+
+# Enable DHCPv6. Note that the prefix-length does not need to be specified
+# and defaults to 64 if missing/
+#dhcp-range=1234::2, 1234::500, 64, 12h
+```
+