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DHCPCD.CONF(5) NetBSD File Formats Manual DHCPCD.CONF(5)
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dhcpcd.conf -- dhcpcd configuration file
Although dhcpcd can do everything from the command line, there are cases
where it's just easier to do it once in a configuration file. Most of
the options found in dhcpcd(8) can be used here. The first word on the
line is the option and the rest of the line is the value. Leading and
trailing whitespace for the option and value are trimmed. You can escape
characters in the value using the \ character. Comments can be prefixed
with the # character. String values should be quoted with the " charac-
Here's a list of available options:
When discovering interfaces, the interface name must match
pattern which is a space or comma separated list of patterns
passed to fnmatch(3). If the same interface is matched in
denyinterfaces then it is still denied.
When discovering interfaces, the interface name must not match
pattern which is a space or comma separated list of patterns
passed to fnmatch(3).
arping address [address]
dhcpcd will arping each address in order before attempting DHCP.
If an address is found, we will select the replying hardware
address as the profile, otherwise the IP address. Example:
# My specific 192.168.0.1 network
# A generic 192.168.0.1 network
authprotocol protocol [algorithm [rdm]]
Authenticate DHCP messages. See the Supported Authentication
Protocols section. If protocol is token then algorithm is
snd_secretid/rcv_secretid so you can send and receive different
authtoken secretid realm expire key
Define a shared key for use in authentication. realm can be ""
to for use with the delayed protocol. expire is the date the
token expires and should be formatted "yyy-mm-dd HH:MM". You can
use the keyword forever or 0 which means the token never expires.
For the token protocol, secretid needs to be 0 and realm needs to
be "". If dhcpcd has the error
dhcp_auth_encode: Invalid argument
then it means that dhcpcd could not find the correct authentica-
tion token in your configuration.
Fork to the background immediately. This is useful for startup
scripts which don't disable link messages for carrier status.
Ignores all packets from address[/cidr].
Only accept packets from address[/cidr]. blacklist is ignored if
whitelist is set.
bootp Be a BOOTP client. Basically, this just doesn't send a DHCP Mes-
sage Type option and will only interact with a BOOTP server. All
other DHCP options still work.
Instructs the DHCP server to broadcast replies back to the
client. Normally this is only set for non-Ethernet interfaces,
such as FireWire and InfiniBand. In most cases, dhcpcd will set
Sets the group ownership of /var/run/dhcpcd.sock so that users
other than root can connect to dhcpcd.
debug Echo debug messages to the stderr and syslog.
Load the value /dev management module. dhcpcd will load the
first one found to work, if any.
Push value to the environment for use in dhcpcd-run-hooks(8).
For example, you can force the hostname hook to always set the
hostname with env force_hostname=YES. Or set which driver
wpa_supplicant(8) should use with env
If the hostname is set, it will be will set to the FQDN if possi-
ble as per RFC 4702, section 3.1. If the FQDN option is missing,
dhcpcd will still try and set a FQDN from the hostname and domain
options for consistency. To override this, set env
hostname_fqdn=[YES|NO|SERVER]. A value of SERVER means just what
the server says, don't manipulate it. This could lead to an
inconsistent hostname on a DHCPv4 and DHCPv6 network where the
DHCPv4 hostname is short and the DHCPv6 has an FQDN. DHCPv6 has
no hostname option.
Send the clientid. If the string is of the format 01:02:03 then
it is encoded as hex. For interfaces whose hardware address is
longer than 8 bytes, or if the clientid is an empty string then
dhcpcd sends a default clientid of the hardware family and the
duid Use a DHCP Unique Identifier. If a system UUID is available,
that will be used to create a DUID-UUID, otheriwse if persistent
storage is available then a DUID-LLT (link local address + time)
is generated, otherwise DUID-LL is generated (link local
address). This, plus the IAID will be used as the clientid. The
DUID generated will be held in /var/db/dhcpcd/duid and should not
be copied to other hosts. This file also takes precedence over
the above rules.
Set the Interface Association Identifier to iaid. This option
must be used in an interface block. This defaults to the VLANID
(prefixed with 0xff) for the interface if set, otherwise the last
4 bytes of the hardware address assigned to the interface. Each
instance of this should be unique within the scope of the client
and dhcpcd warns if a conflict is detected. If there is a con-
flict, it is only a problem if the conflicted IAIDs are used on
the same network.
dhcp Enable DHCP on the interface, on by default.
dhcp6 Enable DHCPv6 on the interface, on by default.
ipv4 Enable IPv4 on the interface, on by default.
ipv6 Enable IPv6 on the interface, on by default.
Request the address in the DHCP DISCOVER message. There is no
guarantee this is the address the DHCP server will actually give.
If no address is given then the first address currently assigned
to the interface is used.
Behaves like request as above, but sends a DHCP INFORM instead of
DISCOVER/REQUEST. This does not get a lease as such, just noti-
fies the DHCP server of the address in use. You should also
include the optional cidr network number in case the address is
not already configured on the interface. dhcpcd remains running
and pretends it has an infinite lease. dhcpcd will not de-con-
figure the interface when it exits. If dhcpcd fails to contact a
DHCP server then it returns a failure instead of falling back on
Performs a DHCPv6 Information Request. No address is requested
or specified, but all other DHCPv6 options are allowed. This is
normally performed automatically when an IPv6 Router Advertise-
ment indicates that the client should perform this operation.
This option is only needed when dhcpcd is not processing IPv6 RA
messages and the need for a DHCPv6 Information Request exists.
dhcpcd normally de-configures the interface and configuration
when it exits. Sometimes, this isn't desirable if, for example,
you have root mounted over NFS or SSH clients connect to this
host and they need to be notified of the host shutting down. You
can use this option to stop this from happening.
Fall back to using this profile if DHCP fails. This allows you
to configure a static profile instead of using ZeroConf.
Sends the hostname name to the DHCP server so it can be regis-
tered in DNS. If name is an empty string then the current system
hostname is sent. If name is a FQDN (i.e., contains a .) then it
will be encoded as such.
Sends the short hostname to the DHCP server instead of the FQDN.
This is useful because DHCP servers will not register the FQDN in
their DNS if the domain part does not match theirs.
Also, see the env option above to control how the hostname is set
on the host.
ia_na [iaid [/ address]]
Request a DHCPv6 Normal Address for iaid. iaid defaults to the
iaid option as described above. You can request more than one
ia_na by specifying a unique iaid for each one.
Request a DHCPv6 Temporary Address for iaid. You can request
more than one ia_ta by specifying a unique iaid for each one.
ia_pd [iaid [/ prefix / prefix_len] [interface [/ sla_id [/ prefix_len [/
Request a DHCPv6 Delegated Prefix for iaid. This option must be
used in an interface block. Unless a sla_id of 0 is assigned
with the same resultant prefix length as the delegation, a reject
route is installed for the Delegated Prefix to stop unallocated
addresses being resolved upstream. If no interface is given then
we will assign a prefix to every other interface with a sla_id
equivalent to the interface index assigned by the OS. Otherwise
addresses are only assigned for each interface and sla_id. Each
assigned address will have a suffix, defaulting to 1. If the
suffix is 0 then a SLAAC address is assigned. You cannot assign
a prefix to the requesting interface unless the DHCPv6 server
supports the RFC 6603 Prefix Exclude Option. dhcpcd has to be
running for all the interfaces it is delegating to. A default
prefix_len of 64 is assumed, unless the maximum sla_id does not
fit. In this case prefix_len is increased to the highest multi-
ple of 8 that can accommodate the sla_id. sla_id is an integer
which must be unique inside the iaid and is added to the prefix
which must fit inside prefix_len less the length of the delegated
prefix. You can specify multiple interface / sla_id / prefix_len
per ia_pd, space separated. IPv6RS should be disabled globally
when requesting a Prefix Delegation.
In the following example eth0 is the externally facing interface
to be configured for both IPv4 and IPv6. The DHCPv4 server will
provide us with an IPv4 address and a default route. The DHCPv6
server is going to provide us with an IPv6 address, a default
route and a /64 subnet to be delegated to the internal interface.
The eth1 interface will be automatically configured for IPv6
using the first address (::1) from the delegated prefix. A sec-
ond prefix is requested and assigned to two other interfaces.
rtadvd(8) can be used with an empty configuration file on eth1,
eth2 and eth3, to provide automatic IPv6 address configuration
for the internal network.
noipv6rs # disable routing solicitation
denyinterfaces eth2 # Don't touch eth2 at all
ipv6rs # enable routing solicitation for eth0
ia_na 1 # request an IPv6 address
ia_pd 2 eth1/0 # request a PD and assign it to eth1
ia_pd 3 eth2/1 eth3/2 # req a PD and assign it to eth2 and eth3
Only configure IPv4.
Only configure IPv6.
fqdn [disable | none | ptr | both]
none will not ask the DHCP server to update DNS. ptr just asks
the DHCP server to update the PTR record of the host in DNS,
whereas both also updates the A record. disable will disable the
FQDN option. The default is both. dhcpcd itself never does any
DNS updates. dhcpcd encodes the FQDN hostname as specified in
Subsequent options are only parsed for this interface.
Generate SLAAC addresses for each Prefix advertised by an IPv6
Router Advertisement message with the Auto flag set. On by
Disables the above option.
By default, when dhcpcd receives an IPv6 Router Advertisement,
dhcpcd will only fork to the background if the RA contains at
least one unexpired RDNSS option and a valid prefix or no DHCPv6
instruction. Set this option so to make dhcpcd always fork on an
ipv6rs Enables IPv6 Router Advertisement solicitation. This is on by
default, but is documented here in the case where it is disabled
globally but needs to be enabled for one interface.
Request a leasetime of seconds.
Override the size of the link receive buffer from the kernel
default. While dhcpcd will recover from link buffer overflows,
this may not be desirable on heavily loaded systems.
Writes to the specified logfile rather than syslog(3). The
logfile is reopened when dhcpcd receives the SIGUSR2 signal.
Metrics are used to prefer an interface over another one, lowest
wins. dhcpcd will supply a default metric of 200 +
if_nametoindex(3). An extra 100 will be added for wireless
Specifies the URL for a Manufacturer Usage Description (MUD).
The description is used by upstream network devices to instanti-
ate any desired access lists. See draft-ietf-opsawg-mud for more
Any pre-existing IPv4 addresses will be removed from the inter-
face when adding a new IPv4 address.
noarp Don't send any ARP requests. This also disables IPv4LL.
Don't require authentication even though we requested it. Also
allows FORCERENEW and RECONFIGURE messages without authentica-
Don't delay for an initial randomised time when starting proto-
nodev Don't load /dev management modules.
nodhcp Don't start DHCP or listen to DHCP messages. This is only useful
when allowing IPv4LL.
Don't start DHCPv6 or listen to DHCPv6 messages. Normally DHCPv6
is started by an IPv6 Router Advertisement instruction or config-
Don't install any default routes.
Install a default route if available (default).
Don't run this hook script. Matches full name, or prefixed with
2 numbers optionally ending with .sh.
So to stop dhcpcd from touching your DNS settings or starting
wpa_supplicant you would do:-
nohook resolv.conf, wpa_supplicant
noipv4 Don't attempt to configure an IPv4 address.
Don't attempt to obtain an IPv4LL address if we failed to get one
via DHCP. See RFC 3927.
noipv6 Don't solicit or accept IPv6 Router Advertisements and DHCPv6.
Don't solicit or accept IPv6 Router Advertisements.
nolink Don't receive link messages about carrier status. You should
only set this for buggy interface drivers.
noup Don't bring the interface up when in master mode. If dhcpcd.conf
cannot determine the carrier state, dhcpcd.conf will enter a
tight polling loop until the interface is marked up and running
or a valid carrier state is reported.
Requests the option from the server. It can be a variable to be
used in dhcpcd-run-hooks(8) or the numerical value. You can
specify more options separated by commas, spaces or more option
lines. Prepend dhcp6_ to option to request a DHCPv6 option. If
no DHCPv6 options are configured, then DHCPv4 options are mapped
to equivalent DHCPv6 options.
Prepend nd_ to option to handle ND options, but this only works
for the nooption, reject and require options.
To see a list of options you can use, call dhcpcd with the -V,
Remove the option from the message before it's processed.
Requires the option to be present in all messages, otherwise the
message is ignored. To enforce that dhcpcd only responds to DHCP
servers and not BOOTP servers, you can require dhcp_message_type.
This isn't an exact science though because a BOOTP server can
send DHCP-like options.
Reject a message that contains the option. This is useful when
you cannot use require to select / de-select BOOTP messages.
If dhcpcd.conf detects an address added to a point to point
interface (PPP, TUN, etc) then it will set the listed DHCP
options to the destination address of the interface.
Subsequent options are only parsed for this profile name.
quiet Suppress any dhcpcd output to the console, except for errors.
Allow reboot seconds before moving to the DISCOVER phase if we
have an old lease to use and moving from DISCOVER to IPv4LL if no
reply. The default is 5 seconds. A setting of 0 seconds causes
dhcpcd to skip the REBOOT phase and go straight into DISCOVER.
This is desirable for mobile users because if you change from
network A to network B and they use the same subnet and the
address from network A isn't in use on network B, then the DHCP
server will remain silent even if authoritative which means
dhcpcd will timeout before moving back to the DISCOVER phase.
dhcpcd will release the lease prior to stopping the interface.
Use script instead of the default /libexec/dhcpcd-run-hooks.
Subsequent options are only parsed for this wireless ssid.
slaac [hwaddr | private]
Selects the interface identifier used for SLAAC generated IPv6
addresses. If private is used, an RFC 7217 address is generated.
Configures a static value. If you set ip_address then dhcpcd
will not attempt to obtain a lease and will just use the value
for the address with an infinite lease time. If you set
ip6_address, dhcpcd will continue auto-configuration as normal.
Here is an example which configures two static address, overrid-
ing the default IPv4 broadcast address, an IPv4 router, DNS and
disables IPv6 auto-configuration. You could also use the inform6
command here if you wished to obtain more information via DHCPv6.
For IPv4, you should use the inform ipaddress option instead of
setting a static address.
Here is an example for PPP which gives the destination a default
route. It uses the special destination keyword to insert the
destination address into the value.
Time out after seconds, instead of the default 30. A setting of
0 seconds causes dhcpcd to wait forever to get a lease. If
dhcpcd is working on a single interface then dhcpcd will exit
when a timeout occurs, otherwise dhcpcd will fork into the back-
ground. If using IPv4LL then dhcpcd start the IPv4LL process
after the timeout and then wait a little longer before really
Tag the DHCPv4 messages with the userclass. You can specify more
Add an encapsulated vendor option. code should be between 1 and
254 inclusive. To add a raw vendor string, omit code but keep
the comma. Examples.
Set the vendor option 01 with an IP address.
Set the vendor option 02 with a hex code.
Set the vendor option 03 with an IP address as a string.
Set un-encapsulated vendor option to hello world.
vendor ,"hello world"
Set the DHCP Vendor Class. DHCPv6 has its own option as shown
below. The default is dhcpcd-<version>:<os>:<machine>:<plat-
form>. For example
If not set then none is sent. Some badly configured DHCP servers
reject unknown vendorclassids. To work around it, try and imper-
sonate Windows by using the MSFT vendorclassid.
vendclass en data
Add the DHCPv6 Vendor Indetifying Vendor Class with the IANA
assigned Enterprise Number en with the data. This option can be
set more than once to add more data, but the behaviour, as per
RFC 3925 is undefined if the Enterprise Number differs.
waitip [4 | 6]
Wait for an address to be assigned before forking to the back-
ground. 4 means wait for an IPv4 address to be assigned. 6
means wait for an IPv6 address to be assigned. If no argument is
given, dhcpcd.conf will wait for any address protocol to be
assigned. It is possible to wait for more than one address pro-
tocol and dhcpcd.conf will only fork to the background when all
waiting conditions are satisfied.
Use the last four bytes of the hardware address as the DHCP xid
instead of a randomly generated number.
Defining new options
DHCP, ND and DHCPv6 allow for the use of custom options, and RFC 3925
vendor options for DHCP can also be supplied. Each option needs to be
started with the define, definend, define6 or vendopt directive. This
can optionally be followed by both embed or encap options. Both can be
specified more than once and embed must come before encap.
define code type variable
Defines the DHCP option code of type with a name of variable
exported to dhcpcd-run-hooks(8).
definend code type variable
Defines the ND option code of type with a name of variable
exported to dhcpcd-run-hooks(8), with a prefix of _nd.
define6 code type variable
Defines the DHCPv6 option code of type with a name of variable
exported to dhcpcd-run-hooks(8), with a prefix of _dhcp6.
vendopt code type variable
Defines the Vendor-Identifying Vendor Options. The code is the
IANA Enterprise Number which will uniquely describe the encapsu-
lated options. type is normally encap. variable names the Ven-
dor option to be exported.
embed type variable
Defines an embedded variable within the defined option. The
length is determined by the type. If the variable is not the
same as defined in the parent option, it is prefixed with the
parent variable first with an underscore. If the variable has
the name of reserved then it is not processed.
encap code type variable
Defines an encapsulated variable within the defined option. The
length is determined by the type. If the variable is not the
same as defined in the parent option, it is prefixed with the
parent variable first with an underscore.
These keywords come before the type itself, to describe it more fully.
You can use more than one, but they must appear in the order listed
request Requests the option by default without having to be specified in
This option cannot be requested, regardless of user configura-
This option is optional. Only makes sense for embedded options
like the client FQDN option, where the FQDN string itself is
index The option can appear more than once and will be indexed.
array The option data is split into a space separated array, each ele-
ment being the same type.
Types to define
The type directly affects the length of data consumed inside the option.
Any remaining data is normally discarded. Lengths can be specified for
string and binhex types, but this is generally with other data embedded
afterwards in the same option.
An IPv4 address, 4 bytes.
An IPv6 address, 16 bytes.
string [: length]
A NVT ASCII string of printable characters.
byte A byte.
A byte represented as a string of flags, most significant bit
first. For example, using ABCDEFGH then A would equal 10000000,
B 01000000, C 00100000, etc. If the bit is not set, the flag is
not printed. A flag of 0 is not printed even if the bit position
is set. This is to allow reservation of the first bits while
assigning the last bits.
int16 A signed 16bit integer, 2 bytes.
uint16 An unsigned 16bit integer, 2 bytes.
int32 A signed 32bit integer, 4 bytes.
uint32 An unsigned 32bit integer, 4 bytes.
flag A fixed value (1) to indicate that the option is present, 0
domain An RFC 3397 encoded string.
dname An RFC 1035 validated string.
binhex [: length]
Binary data expressed as hexadecimal.
embed Contains embedded options (implies encap as well).
encap Contains encapsulated options (implies embed as well).
option References an option from the global definition.
# DHCP option 81, Fully Qualified Domain Name, RFC 4702
define 81 embed fqdn
embed byte flags
embed byte rcode1
embed byte rcode2
embed domain fqdn
# DHCP option 125, Vendor Specific Information Option, RFC 3925
define 125 encap vsio
embed uint32 enterprise_number
# Options defined for the enterprise number
encap 1 ipaddress ipaddress
Supported Authentication Protocols
token Sends a plain text token the server expects and matches a token
sent by the server. The tokens do not have to be the same. If
unspecified, the token with a secretid of 0 will be used in
sending messages and validating received messages.
Delayed Authentication. dhcpcd will send an authentication
option with no key or MAC. The server will see this option, and
select a key for dhcpcd.conf, writing the realm and secretid in
it. dhcpcd will then look for an unexpired token with a match-
ing realm and secretid. This token is used to authenticate all
delayed Same as above, but without a realm.
Supported Authentication Algorithms
If none specified, hmac-md5 is the default.
Supported Replay Detection Mechanisms
If none specified, monotonic is the default. If this is changed from
what was previously used, or the means of calculating or storing it is
broken, then the DHCP server will probably have to have its notion of the
client's Replay Detection Value reset.
Read the number in the file /var/db/dhcpcd/dhcpcd-rdm.monotonic
and add one to it.
Create an NTP timestamp from the system time.
Same as monotime.
fnmatch(3), if_nametoindex(3), dhcpcd(8), dhcpcd-run-hooks(8)
Roy Marples <email@example.com>
Please report them to
NetBSD 9.2 November 15, 2019 NetBSD 9.2