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// This is an example configuration file for DHCPv4 server in Kea.
// It covers some of the more advanced features. This file may not be coherent
// as its main purpose is to demonstrate the features. They don't necessarily
// have to make sense used together.
// The new parser supports 3 comment styles:
// This is C++ style.
# This is a bash style.
/* This is a C style comment. */
/* C style comment
can span
multiple lines */
{ "Dhcp4":
{
// Kea is told to listen on eth0 interface only.
"interfaces-config": {
"interfaces": [ "eth0" ],
// This specifies what type of socket Kea uses. Currently supported
// are 'raw' (which is the default) and 'udp'. Raw has the benefit
// of receiving all traffic every time and a downside of bypassing
// all firewall rules and having marginally bigger performance impact.
// 'udp' is generally better if you have only relayed traffic. Kea
// than opens up normal UDP socket and the kernel does all the
// Ethernet/IP stack processing.
"dhcp-socket-type": "udp",
// Typically the DHCP server will send its response back on the same
// interface the query came in. This is the default ("same-as-inbound").
// However, sometimes it is useful to have the ability to send the
// packet as plain UDP packet and let the kernel and the routing tables
// determine the right interface ("use-routing"). This option only works
// for "dhcp-socket-type" set to "udp" and is ignored otherwise.
"outbound-interface": "use-routing",
// This makes interfaces to be re-detected at each (re-)configuration.
// By default it is true.
"re-detect": true
},
"sanity-checks": {
// This parameter determines what to do when a new lease appears in the
// system (i.e. either is read from disk during memfile startup or is
// added via lease commands). There are five modes supported:
// none - do nothing, accept them as is
// warn - if subnet-id problems are detected, print a warning, but
// otherwise load the lease as is. This is the default value.
// fix - attempt to fix the lease by finding appropriate subnet-id value.
// if there is no suitable subnet, the lease is loaded as is.
// fix-del - attempt to fix the lease by finding appropriate subnet-id
// value. If there is no suitable subnet, the lease is deleted.
// del - delete leases that have incorrect subnet-id values.
"lease-checks": "fix-del"
},
// Option 43 last resort definition can make well-formed messages
// to be rejected because they use not compatible "raw" value,
// and different vendors may define different sub-options.
// The option definition should be applied to avoid these problems,
// for instance by defining at the global scope the option as binary.
// In client-classes the option may be redefined as carrying vendor
// dependent sub-options.
"option-def": [ {
"name": "vendor-encapsulated-options",
"code": 43,
"type": "binary"
} ],
// We need to specify the database used to store leases. As of
// June 2022, three database backends are supported: MySQL,
// PostgreSQL and the in-memory database, Memfile.
// We'll use memfile because it doesn't require any prior set up.
// For memfile, it's important to always specify lfc-interval, so
// the lease file would not grow without bounds and be sanitized
// once per hour.
"lease-database": {
"type": "memfile",
"lfc-interval": 3600
},
// This defines a control socket. If defined, Kea will open a UNIX socket
// and will listen for incoming commands. See section 15 of the Kea User's
// Guide for list of supported commands.
"control-socket": {
"socket-type": "unix",
"socket-name": "/tmp/kea4-ctrl-socket"
},
// Addresses will be assigned with a lifetime of 4000 seconds.
// The client is told to start renewing after 1000 seconds. If the server
// does not respond within 2000 seconds of the lease being granted, client
// is supposed to start REBIND procedure (emergency renewal that allows
// switching to a different server).
"valid-lifetime": 4000,
"renew-timer": 1000,
"rebind-timer": 2000,
// RFC6842 says that the server is supposed to echo back client-id option.
// However, some older clients do not support this and are getting confused
// when they get their own client-id. Kea can disable RFC6842 support.
"echo-client-id": false,
// Some clients don't use stable client identifier, but rather
// generate them during each boot. This may cause a client that
// reboots frequently to get multiple leases, which may not be
// desirable. As such, sometimes admins prefer to tell their DHCPv4
// server to ignore client-id value altogether and rely exclusively
// on MAC address. This is a parameter that is defined globally, but
// can be overridden on a subnet level.
"match-client-id": true,
// By default, Kea ignores requests by clients for unknown IP addresses,
// because other non-cooperating DHCP servers could reside on the same
// network (RFC 2131). This parameter is defined globally, but can be
// overridden on a subnet level
"authoritative": false,
// The following list defines subnets. Each subnet consists of at
// least subnet and pool entries. One extra feature that requires
// some explanation is user-context. This is a structure that you can
// define in subnets, pools and others. It is parsed by Kea, but not
// used directly. It is intended to keep anything you may want to
// put there - comments, extra designations, floor or department
// names etc. These structures will be made available to Kea hooks.
// A comment entry is translated into a user-context with a
// "comment" property so you can include comments inside the
// configuration itself.
"subnet4": [
{
"pools": [ {
"pool": "192.0.2.1 - 192.0.2.200",
"user-context": { "info": "what a large pool" }
} ],
"subnet": "192.0.2.0/24",
"user-context": {
"comment": "Our first subnet!"
}
// Equivalent using smart parser
// "comment": "Our first subnet!"
},
{
// This particular subnet has match-client-id value changed.
// This causes Kea to ignore client-id values in this subnet
// and rely exclusively on MAC addresses.
"pools": [ { "pool": "192.0.3.100 - 192.0.3.200" } ],
"subnet": "192.0.3.0/24",
"match-client-id": false
},
{
"pools": [ { "pool": "192.0.4.1 - 192.0.4.254" } ],
"subnet": "192.0.4.0/24",
// Sometimes the relay may use an IPv4 address that does
// not match the subnet. This is discouraged, but there are
// valid cases when it makes sense. One case is when there
// is a shared subnet.
"relay": {
"ip-address": "192.168.1.1"
}
},
{
// This particular subnet has the authoritative value changed.
// This causes Kea to reply to requests for unknown IP addresses
// with a DHCPNAK message.
"pools": [ { "pool": "192.0.5.100 - 192.0.5.200" } ],
"subnet": "192.0.5.0/24",
"authoritative": true
}
],
// The following configures logging. It assumes that messages with
// at least informational level (info, warn, error and fatal) should
// be logged to stdout.
"loggers": [
{
"name": "kea-dhcp4",
"output_options": [
{
"output": "stdout",
// Several additional parameters are possible in addition
// to the typical output. Flush determines whether logger
// flushes output to a file. Maxsize determines maximum
// filesize before the file is being rotated. maxver
// specifies the maximum number of rotated files being
// kept.
"flush": true,
"maxsize": 204800,
"maxver": 4,
// We use pattern to specify custom log message layout
"pattern": "%d{%y.%m.%d %H:%M:%S.%q} %-5p [%c/%i] %m\n"
}
],
"severity": "INFO"
}
]
}
}
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