Kea DHCP
Summary
ISC Kea is an open-source, high-performance Dynamic Host Configuration Protocol (DHCP) server developed by the Internet Systems Consortium (ISC). It is designed to provide DHCP services for IPv4 and IPv6 networks, including the allocation of IP addresses, network configuration parameters, and dynamic updates. ISC Kea is the successor to ISC's earlier DHCP server software, ISC DHCP, and is built to offer improved scalability, flexibility, and extensibility.
Configuration
Control
Info: keactrl is only available if you compile kea from source.
Get DHCP4 Server Status
keactrl status -s dhcp4
Reload DHCP4 Server
You'll want to do this after making changes to the kea-dhcp4.conf file.
keactrl reload -s dhcp4
Leases
Leases are stored in memfile, by default. But you can also have them written to a CSV file:
"lease-database": {
"type": "memfile", // write leases to memfile...
"persist": true,
"name": "/tmp/kea-leases4.csv", // ...but also write them to csv
"lfc-interval": 3600,
"max-row-errors": 100
},
MySQL
To use host reservations from MySQL, you need to add the "hosts-database" section to the "Dhcp4" section of the config file, like this:
"hosts-database": {
"type": "mysql",
"name": "kea_db",
"user": "kea-user",
"password": "{password}",
"host": "localhost",
"port": 3306
},
Subnet-Ids need to be defined in your subnet declarations, too.
You can use both the hosts database and the configuration file for host reservations at the same time.
IPv4 Reservations
SELECT host_id,dhcp_identifier,dhcp4_subnet_id,ipv4_address,hostname FROM hosts;
Insert Statement Example:
START TRANSACTION;
SET @ipv4_reservation='10.10.0.16';
SET @hostname = 'hostname';
SET @identifier_type='hw-address';
SET @identifier_value='be:ef:be:ef:be:ef';
SET @dhcp4_subnet_id=10;
INSERT INTO hosts (dhcp_identifier,
dhcp_identifier_type,
dhcp4_subnet_id,
ipv4_address,
hostname)
VALUES (UNHEX(REPLACE(@identifier_value, ':', '')),
(SELECT type FROM host_identifier_type WHERE name=@identifier_type),
@dhcp4_subnet_id,
INET_ATON(@ipv4_reservation),
@hostname);
COMMIT;
Info: IP Address get stored in the db in decimal format.
Manual Dump of Host Reservations
mysqldump -u kea-user -p kea_db hosts > kea-hosts.sql
Sync db From Primary to Standby Peers
Follow the steps below to configure a Standby peer to sync its hosts db from the Primary peer. We will create a MySQL user kea-xfer with just enough privileges to be able to sync the hosts table.
Info: Assume that net1 is the Primary and net2 is the Standby peer you want to sync to.
Do on Primary Peer
CREATE USER 'kea-xfer'@'localhost' IDENTIFIED BY '{password}';
CREATE USER 'kea-xfer'@'net2.lambnet.us' IDENTIFIED BY '{password}';
GRANT SELECT ON `kea_db`.`hosts` TO 'kea-xfer'@'localhost';
GRANT SELECT ON `kea_db`.`hosts` TO 'kea-xfer'@'net2.lambnet.us';
Do on Standby Peer
CREATE USER 'kea-xfer'@'localhost' IDENTIFIED BY '{password}';
GRANT LOCK TABLES ON `kea_db`.* TO `kea-xfer`@`localhost`;
GRANT REFERENCES ON `kea_db`.`host_identifier_type` TO `kea-xfer`@`localhost`;
GRANT SELECT, INSERT, CREATE, DROP, ALTER ON `kea_db`.`hosts` TO `kea-xfer`@`localhost`;
Crontab for use on Standby peers
Use this crontab to automatically sync a Standby peer with the Primary peer's kea_db.hosts table (i.e., push from Primary to Standby).
*/5 * * * * mysqldump -h net1.lambnet.us -u kea-xfer -p{password} --single-transaction --no-tablespaces kea_db hosts | mysql -u kea-xfer -p{password} kea_db
MySQL Performance Tuning
Configure in /etc/mysql/my.cnf:
[mysqld] innodb_flush_log_at_trx_commit=2
SystemD Tip
You may encounter an issue where kea-dhcp4 fails to start at boot. Try adding this to /usr/lib/systemd/system/kea-dhcp4.service, at the end of the [Unit] section:
After=mysqld.service
Kea-Shell
Commands
[ { "arguments": [ "build-report", "config-backend-pull", "config-get", "config-reload", "config-set", "config-test", "config-write", "dhcp-disable", "dhcp-enable", "ha-continue", "ha-heartbeat", "ha-maintenance-cancel", "ha-maintenance-notify", "ha-maintenance-start", "ha-reset", "ha-scopes", "ha-sync", "ha-sync-complete-notify", "lease4-add", "lease4-del", "lease4-get", "lease4-get-all", "lease4-get-by-client-id", "lease4-get-by-hostname", "lease4-get-by-hw-address", "lease4-get-page", "lease4-resend-ddns", "lease4-update", "lease4-wipe", "lease6-add", "lease6-bulk-apply", "lease6-del", "lease6-get", "lease6-get-all", "lease6-get-by-duid", "lease6-get-by-hostname", "lease6-get-page", "lease6-resend-ddns", "lease6-update", "lease6-wipe", "leases-reclaim", "libreload", "list-commands", "server-tag-get", "shutdown", "statistic-get", "statistic-get-all", "statistic-remove", "statistic-remove-all", "statistic-reset", "statistic-reset-all", "statistic-sample-age-set", "statistic-sample-age-set-all", "statistic-sample-count-set", "statistic-sample-count-set-all", "status-get", "version-get" ], "result": 0 } ]
Get Status
kea-shell --host net2.lambnet.us --service dhcp4 status-get
Info: Don't forget to press Ctrl+D after sending a kea-shell command.