Installation of ISC Kea DHCP Server
First fix detection of Python-3.12 by the build system:
sed -e 's/:3/:4/' \
-i configure
Remove one installation step that uses an obsolete python module:
sed -e '/dlist="/d' \
-i src/bin/shell/Makefile.in
Install ISC Kea DHCP Server by running the following commands:
./configure --prefix=/usr \
--sysconfdir=/etc \
--localstatedir=/var \
--enable-shell \
--with-openssl \
--disable-static \
--docdir=/usr/share/doc/kea-2.4.1 &&
make
To test the results, you must have installed GoogleTest and kept its source. You should also have passed --with-gtest-source=/path/to/googletest/sourcedir to configure above. Run the tests with make check. Three tests in the TLSTest suite are known to fail.
To install the ISC Kea DHCP Server suite, issue the following commands as the root user:
make -j1 install
Command Explanations
--enable-shell: Allows building kea-shell, a command line interface for the control agent.
--with-openssl: Allows using OpenSSL for communicating with the control-agent and for DNS updates.
--disable-static: This switch prevents installation of static versions of the libraries.
--with-pgsql or --with-mysql: ISC Kea can store the leases on a database. This might be useful in large environments running a cluster of DHCP servers. Using the memfile backend (which is a CSV file stored locally) is possible anyhow.
--enable-generate-docs: If documentation is to be rebuilt, add that option. Several dependencies must be installed for generating the documentation.
make -j1 install: ISC does not recommend any form of parallel or job server options when doing the install.
Configuring ISC Kea DHCP Server
The support of IPv4, IPv6 and DDNS has been split into separate servers which runs independently from each other. Each of them has its own configuration file. Additional configuration files come from the keactrl agent which is used to control the servers in an easy way.
Consult the Kea Administrator Reference Manual for detailed information about the configuration of ISC Kea as it is a quite capable system. The configuration shown below is a bare minimum to get a DHCP server running but it already includes configuration for DDNS (Dynamic DNS). That setup might be working for small networks with a few clients and low traffic. For greater installations with thousands of clients, ISC Kea can be configured to use databases (mariadb or postgresql) to store the leases and build a cluster with multiple nodes. It can be integrated to ISC Stork which is a management dashboard to ISC Kea.
If you want to start the DHCP Server at boot, install the /etc/rc.d/init.d/kea-dhcpd init script included in the blfs-bootscripts-20231119 package:
make install-kea-dhcpd
Config Files
/etc/kea/keactrl.conf, /etc/kea/kea-ctrl-agent.conf, /etc/kea/kea-dhcp4.conf, /etc/kea/kea-dhcp6.conf, and /etc/kea/kea-dhcp-ddns.conf
Kea Control Configuration
keactrl is used to control the independent servers (IPv4, IPv6, DDNS). Its configuration file /etc/kea/keactrl.conf is installed by default and includes many path settings which are defined due to the configure at build time. It also includes settings to specify which of the servers should be started.
-
Control Agent
The Control Agent is a daemon which allows the (re)configuration of the Kea DHCP service via REST API. Set ctrl_agent=yes to start the control agent (service providing a REST API), set ctrl_agent=no in case the control agent is not needed.
-
IPv4 DHCP server
This daemon handles requests for IPv4 addresses. Set dhcp4=yes to start it, set dhcp4=no in case DHCP service for IPv4 is not wanted.
-
IPv6 DHCP server
This daemon handles requests for IPv6 addresses. Set dhcp6=yes to start it, set dhcp6=no in case DHCP service for IPv6 is not wanted.
-
Dynamic DNS
This daemon is used to update a DNS server dynamically when Kea assigns an IP address to a device. Set dhcp_ddns=yes to enable it, set dhcp_ddns=no in case dynamic DNS updates are not wanted.
The Netconf service is not installed because required dependencies are not covered by the current BLFS book. .
With the following command, Kea will be configured to start the dhcp service for IPv4 and the dynamic DNS update, while the control agent and the dhcp service for IPv6 remain down. Tweak the command to match your needs on started services and execute as the root user:
sed -e "s/^dhcp4=.*/dhcp4=yes/" \
-e "s/^dhcp6=.*/dhcp6=no/" \
-e "s/^dhcp_ddns=.*/dhcp_ddns=yes/" \
-e "s/^ctrl_agent=.*/ctrl_agent=no/" \
-i /etc/kea/keactrl.conf
Control Agent Configuration
The provided configuration could be used without changes but in BLFS, objects like sockets are stored in /run rather than in /tmp.
cat > /etc/kea/kea-ctrl-agent.conf << "EOF"
// Begin /etc/kea/kea-ctrl-agent.conf
{
// This is a basic configuration for the Kea Control Agent.
// RESTful interface to be available at http://127.0.0.1:8000/
"Control-agent": {
"http-host": "127.0.0.1",
"http-port": 8000,
"control-sockets": {
"dhcp4": {
"socket-type": "unix",
"socket-name": "/run/kea4-ctrl-socket"
},
"dhcp6": {
"socket-type": "unix",
"socket-name": "/run/kea6-ctrl-socket"
},
"d2": {
"socket-type": "unix",
"socket-name": "/run/kea-ddns-ctrl-socket"
}
},
"loggers": [
{
"name": "kea-ctrl-agent",
"output_options": [
{
"output": "/var/log/kea-ctrl-agent.log",
"pattern": "%D{%Y-%m-%d %H:%M:%S.%q} %-5p %m\n"
}
],
"severity": "INFO",
"debuglevel": 0
}
]
}
}
// End /etc/kea/kea-ctrl-agent.conf
EOF
IPv4 DHCP Server Configuration
A sample configuration file is created in /etc/kea/kea-dhcp4.conf. Adjust the file to suit your needs or overwrite it by running the following command as the root user (you'll need to edit this file anyway: at least the interfaces field, the ddns-qualifying-suffix field, and almost all the fields in Subnet4:
cat > /etc/kea/kea-dhcp4.conf << "EOF"
// Begin /etc/kea/kea-dhcp4.conf
{
"Dhcp4": {
// Add names of your network interfaces to listen on.
"interfaces-config": {
"interfaces": [ "eth0", "eth2" ]
},
"control-socket": {
"socket-type": "unix",
"socket-name": "/run/kea4-ctrl-socket"
},
"lease-database": {
"type": "memfile",
"lfc-interval": 3600
},
"expired-leases-processing": {
"reclaim-timer-wait-time": 10,
"flush-reclaimed-timer-wait-time": 25,
"hold-reclaimed-time": 3600,
"max-reclaim-leases": 100,
"max-reclaim-time": 250,
"unwarned-reclaim-cycles": 5
},
"renew-timer": 900,
"rebind-timer": 1800,
"valid-lifetime": 3600,
// Enable DDNS - Kea will dynamically update the DNS
"ddns-send-updates" : true,
"ddns-qualifying-suffix": "your.domain.tld",
"dhcp-ddns" : {
"enable-updates": true
},
"subnet4": [
{
"subnet": "192.168.56.0/24",
"pools": [ { "pool": "192.168.56.16 - 192.168.56.254" } ],
"option-data": [
{
"name": "domain-name",
"data": "your.domain.tld"
},
{
"name": "domain-name-servers",
"data": "192.168.56.2, 192.168.3.7"
},
{
"name": "domain-search",
"data": "your.domain.tld"
},
{
"name": "routers",
"data": "192.168.56.2"
}
]
}
],
"loggers": [
{
"name": "kea-dhcp4",
"output_options": [
{
"output": "/var/log/kea-dhcp4.log",
"pattern": "%D{%Y-%m-%d %H:%M:%S.%q} %-5p %m\n"
}
],
"severity": "INFO",
"debuglevel": 0
}
]
}
}
// End /etc/kea/kea-dhcp4.conf
EOF
IPv6 DHCP Server Configuration
The configuration for IPv6 is similar to the configuration of IPv4. The configuration file is /etc/kea/kea-dhcp6.conf.
Dynamic DNS Configuration
If there is a BIND-9.18.21 server running, ISC Kea can update the DNS when it gives an IP address to a client. A sample configuration file is created in /etc/kea/kea-dhcp-ddns.conf. Adjust the file to suit your needs or overwrite it by running the following command as the root user:
cat > /etc/kea/kea-dhcp-ddns.conf << "EOF"
// Begin /etc/kea/kea-dhcp-ddns.conf
{
"DhcpDdns": {
"ip-address": "127.0.0.1",
"port": 53001,
"control-socket": {
"socket-type": "unix",
"socket-name": "/run/kea-ddns-ctrl-socket"
},
"tsig-keys": [
{
"name" : "rndc-key",
"algorithm" : "hmac-sha256",
"secret" : "1FU5hD7faYaajQCjSdA54JkTPQxbbPrRnzOKqHcD9cM="
}
],
"forward-ddns" : {
"ddns-domains" : [
{
"name" : "your.domain.tld.",
"key-name": "rndc-key",
"dns-servers" : [
{
"ip-address" : "127.0.0.1",
"port" : 53
}
]
}
]
},
"reverse-ddns" : {
"ddns-domains" : [
{
"name" : "56.168.192.in-addr.arpa.",
"key-name": "rndc-key",
"dns-servers" : [
{
"ip-address" : "127.0.0.1",
"port" : 53
}
]
}
]
},
"loggers": [
{
"name": "kea-dhcp-ddns",
"output_options": [
{
"output": "/var/log/kea-ddns.log",
"pattern": "%D{%Y-%m-%d %H:%M:%S.%q} %-5p %m\n"
}
],
"severity": "INFO",
"debuglevel": 0
}
]
}
}
// End /etc/kea/kea-dhcp-ddns.conf
EOF
![[Note]](../images/note.png)
Note
The value of secret is just an example. Generate the key for your installation by using the rndc-confgen -a command or the tsig-keygen command which both are provided by BIND-9.18.21.
In this example configuration, it is assumed that the DNS server runs on the same machine as Kea does (accessible via 127.0.0.1) and that this machine has the IP 192.168.56.2.