# dhcpcd.conf - dhcpcd configuration file - man(5) - [phpMan] [_DHCPCD.CONF_(5)](https://www.chedong.com/phpMan.php/man/DHCPCD.CONF/5/markdown) File Formats Manual [_DHCPCD.CONF_(5)](https://www.chedong.com/phpMan.php/man/DHCPCD.CONF/5/markdown) ## NAME dhcpcd.conf — dhcpcd configuration file ## DESCRIPTION Although **dhcpcd **can do everything from the command line, there are cases where it's just eas‐ ier to do it once in a configuration file. Most of the options found in [_dhcpcd_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd/8/markdown) 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 charac‐ ters in the value using the \ character. Comments can be prefixed with the # character. String values should be quoted with the " character. Here's a list of available options: **allowinterfaces _**pattern_ When discovering interfaces, the interface name must match _pattern_ which is a space or comma separated list of patterns passed to [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown). If the same interface is matched in **denyinterfaces **then it is still denied. **denyinterfaces _**pattern_ When discovering interfaces, the interface name must not match _pattern_ which is a space or comma separated list of patterns passed to [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown). ### anonymous Enables Anonymity Profiles for DHCP, RFC 7844. Any DUID is ignored and ClientID is set to LL only. All non essential options are then masked at this point, but they could be unmasked by explicitly requesting the option **after **the **anonymous **option is processed. As such, the **anonymous **option **should **be the last option in the configura‐ tion unless you really want to send something which could identify you. **dhcpcd **will not try and reboot an old lease, it will go straight into DISCOVER/SOLICIT. ### randomise_hwaddr Forces a hardware address randomisation when the interface is brought up or when the carrier is lost. This is generally used in tandem with the anonymous option. **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: interface bge0 arping 192.168.0.1 # My specific 192.168.0.1 network profile dd:ee:aa:dd:bb:ee static ip_address=192.168.0.10/24 # A generic 192.168.0.1 network profile 192.168.0.1 static ip_address=192.168.0.98/24 **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 re‐ ceive different tokens. **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 ex‐ pires. 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 authentication token in your configuration. ### background Fork to the background immediately. This is useful for startup scripts which don't disable link messages for carrier status. **blacklist _**address_[/cidr] Ignores all packets from _address_[/cidr]. **whitelist _**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 Message Type option and will only interact with a BOOTP server. All other DHCP options still work. ### broadcast 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 this automatically. **controlgroup _**group_ Sets the group ownership of _/run/dhcpcd/sock_ so that users other than root can con‐ nect to **dhcpcd**. **debug **Echo debug messages to the stderr and syslog. **dev _**value_ Load the _value_ _/dev_ management module. **dhcpcd **will load the first one found to work, if any. **env _**value_ Push _value_ to the environment for use in [_dhcpcd-run-hooks_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown). 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)](https://www.chedong.com/phpMan.php/man/wpasupplicant/8/markdown) should use with **env _**wpa_supplicant_driver=nl80211_ If the hostname is set, it will be will set to the FQDN if possible 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. **clientid _**string_ 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 fam‐ ily and the hardware address. **duid **[ll | lt | uuid | value] Use a DHCP Unique Identifier. If a system UUID is available, that will be used to create a DUID-UUID, otherwise if persistent storage is available then a DUID-LLT (link local address + time) is generated, otherwise DUID-LL is generated (link local address). The DUID type can be hinted as an optional parameter if the file _/var/lib/dhcpcd/duid_ does not exist. If not _ll_, _lt_ or _uuid_ then _value_ will be con‐ verted from 00:11:22:33 format. This, plus the IAID will be used as the **clientid**. The DUID generated will be held in _/var/lib/dhcpcd/duid_ and should not be copied to other hosts. This file also takes precedence over the above rules except for setting a value. **iaid _**iaid_ 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 conflict, 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 **[_address_] 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. **inform **[_address_[_/cidr_[_/broadcast_address_]]] Behaves like **request **as above, but sends a DHCP INFORM instead of DISCOVER/REQUEST. This does not get a lease as such, just notifies 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-configure the interface when it exits. If **dhcpcd **fails to contact a DHCP server then it returns a failure instead of falling back on IPv4LL. ### inform6 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 Advertisement 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. ### persistent **dhcpcd **normally de-configures the interface and configuration when it exits. Some‐ times, 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. **fallback _**profile_ Fall back to using this profile if DHCP fails. This allows you to configure a static profile instead of using ZeroConf. **hostname _**name_ Sends the hostname _name_ to the DHCP server so it can be registered 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. ### hostname_short Sends the short hostname to the DHCP server instead of the FQDN. This is useful be‐ cause 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 de‐ scribed above. You can request more than one ia_na by specifying a unique _iaid_ for each one. **ia_ta **[_iaid_] 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_ [/ _suffix_]]]]] 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 as‐ signed by the OS. Otherwise addresses are only assigned for each _interface_ and _sla_id_. To avoid delegating to any interface, use - as the invalid interface name. 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 in‐ creased to the highest multiple 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 mul‐ tiple _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 de‐ fault route. The DHCPv6 server is going to provide us with an IPv6 address, a de‐ fault route and a /64 subnet to be delegated to the internal interface. The eth1 in‐ terface will be automatically configured for IPv6 using the first address (::1) from the delegated prefix. A second prefix is requested and assigned to two other inter‐ faces. [_rtadvd_(8)](https://www.chedong.com/phpMan.php/man/rtadvd/8/markdown) 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 interface eth0 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 ia_pd 4 - # request a PD but don't assign it ### ipv4only Only configure IPv4. ### ipv6only 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 **RFC 1035**. **interface _**interface_ Subsequent options are only parsed for this _interface_. ### ipv6ra_autoconf Generate SLAAC addresses for each Prefix advertised by an IPv6 Router Advertisement message with the Auto flag set. On by default. ### ipv6ra_noautoconf Disables the above option. ### ipv6ra_fork 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 a RA. **ipv6rs **Enables IPv6 Router Advertisement solicitation. This is on by default, but is docu‐ mented here in the case where it is disabled globally but needs to be enabled for one interface. **leasetime _**seconds_ Request DHCP a lease time of _seconds_. _-1_ represents an infinite lease time. By de‐ fault **dhcpcd **does not request any lease time and leaves it in the hands of the DHCP server. It is not possible to request a DHCPv6 lease time as this is not RFC compli‐ ant. See RFC 8415 21.4, 21.6, 21.21 and 21.22. **link_rcvbuf _**size_ 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. **logfile _**logfile_ Writes to the specified _logfile_. **dhcpcd **still writes to [_syslog_(3)](https://www.chedong.com/phpMan.php/man/syslog/3/markdown). The _logfile_ is reopened when **dhcpcd **receives the SIGUSR2 signal. **metric _**metric_ Metrics are used to prefer an interface over another one, lowest wins. **dhcpcd **will supply a default metric of 1000 + [_if_nametoindex_(3)](https://www.chedong.com/phpMan.php/man/ifnametoindex/3/markdown). This will be offset by 2000 for wireless interfaces, with additional offsets of 1000000 for IPv4LL and 2000000 for roaming interfaces. **mudurl _**url_ Specifies the URL for a Manufacturer Usage Description (MUD). The description is used by upstream network devices to instantiate any desired access lists. See draft- ietf-opsawg-mud for more information. ### noalias Any pre-existing IPv4 addresses will be removed from the interface when adding a new IPv4 address. **noarp **Don't send any ARP requests. This also disables IPv4LL. ### noauthrequired Don't require authentication even though we requested it. Also allows FORCERENEW and RECONFIGURE messages without authentication. ### nodelay Don't delay for an initial randomised time when starting protocols. **nodev **Don't load _/dev_ management modules. **nodhcp **Don't start DHCP or listen to DHCP messages. This is only useful when allowing IPv4LL. ### nodhcp6 Don't start DHCPv6 or listen to DHCPv6 messages. Normally DHCPv6 is started by an IPv6 Router Advertisement instruction or configuration. ### nogateway Don't install any default routes. ### gateway Install a default route if available (default). **nohook _**script_ 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. ### noipv4ll 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. ### noipv6rs 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 manager mode. **option _**option_ Requests the _option_ from the server. It can be a variable to be used in [_dhcpcd-run-hooks_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown) or the numerical value. You can specify more _option_s 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**, **--variables **argument. **nooption _**option_ Remove the option from the message before it's processed. **require _**option_ 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 _**option_ Reject a message that contains the _option_. This is useful when you cannot use **require **to select / de-select BOOTP messages. **destination _**option_ 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. **profile _**name_ Subsequent options are only parsed for this profile _name_. **quiet **Suppress any dhcpcd output to the console, except for errors. **reboot _**seconds_ Allow _reboot_ seconds before moving to the DISCOVER phase if we have an old lease to use. Allow _reboot_ seconds before starting fallback states from the DISCOVER phase. IPv4LL is started when the first _reboot_ timeout is reached. The default is 5 sec‐ onds. A setting of 0 seconds causes **dhcpcd.conf **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 authori‐ tative which means **dhcpcd **will timeout before moving back to the DISCOVER phase. This has no effect on DHCPv6 other than skipping the reboot phase. ### release **dhcpcd **will release the lease prior to stopping the interface. **script _**script_ Use _script_ instead of the default _/usr/lib/dhcpcd/dhcpcd-run-hooks_. **ssid _**ssid_ Subsequent options are only parsed for this wireless _ssid_. **slaac hwaddr **| **private **| **token _**token_ [**temp **| **temporary**] Selects the interface identifier used for SLAAC generated IPv6 addresses. If **private** is used, a RFC 7217 address is generated. If **token _**token_ is used then the token is combined with the prefix to make the final address. The **temporary **directive will create a temporary address for the prefix as well. **static _**value_ Configures a static _value_. If you set **ip_address **then **dhcpcd **will not attempt to ob‐ tain a lease and will just use the value for the address with an infinite lease time. If you set an empty value this removes all prior static allocations to the same value. This is useful when using profiles and in the case of **ip_address **it will re‐ move the static allocation. Note that setting 0.0.0.0 keeps the static allocation but waits for a 3rdparty to configure the address. If you set **ip6_address**, **dhcpcd** will continue auto-configuration as normal. Here is an example which configures two static address, overriding 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. interface eth0 noipv6rs static ip_address=192.168.0.10/24 static broadcast_address=192.168.0.63 static ip6_address=fd51:42f8:caae:[d92e::ff](https://www.chedong.com/phpMan.php/perldoc/d92e%3A%3Aff/markdown)/64 static routers=192.168.0.1 static domain_name_servers=192.168.0.1 fd51:42f8:caae:[d92e::1](https://www.chedong.com/phpMan.php/perldoc/d92e%3A%3A1/markdown) 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. interface ppp0 static ip_address=0.0.0.0 destination routers **timeout _**seconds_ 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 background. If using IPv4LL then **dhcpcd **start the IPv4LL process after the timeout and then wait a little longer before really timing out. **userclass _**string_ Tag the DHCPv4 message with the userclass. You can specify more than one. **msuserclass _**string_ Tag the DHCPv4 mesasge with the Microsoft userclass. Unlike the **userclass **option, this one can only be added once. It should only be used for Microsoft DHCP servers and the **vendorclassid **should be set to "MSFT 98" or "MSFT 5.0". This option is not RFC compliant. **vendor _**code_,_value_ 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. vendor 01,192.168.0.2 Set the vendor option 02 with a hex code. vendor 02,01:02:03:04:05 Set the vendor option 03 with an IP address as a string. vendor 03,\"192.168.0.2\" Set un-encapsulated vendor option to hello world. vendor ,"hello world" **vendorclassid _**string_ Set the DHCP Vendor Class. DHCPv6 has its own option as shown below. The default is dhcpcd-:::. For example dhcpcd-5.5.6:NetBSD-6.99.5:i386:i386 If not set then none is sent. Some badly configured DHCP servers reject unknown ven‐ dorclassids. To work around it, try and impersonate Windows by using the MSFT ven‐ dorclassid. **vendclass _**en_ _data_ Add the DHCPv6 Vendor Indetifying Vendor Class with the IANA assigned Enterprise Num‐ ber _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 background. 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 as‐ signed. It is possible to wait for more than one address protocol and **dhcpcd.conf** will only fork to the background when all waiting conditions are satisfied. ### xidhwaddr 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)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown). **definend _**code_ _type_ _variable_ Defines the ND option _code_ of _type_ with a name of _variable_ exported to [_dhcpcd-run-hooks_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown), 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)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown), with a prefix of _dhcp6__. **vendopt _**code_ _type_ _variable_ Defines the Vendor-Identifying Vendor Options. The _code_ is the IANA Enterprise Num‐ ber which will uniquely describe the encapsulated options. _type_ is normally _encap_. _variable_ names the Vendor 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. ### Type prefix 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 below. **request **Requests the option by default without having to be specified in user configuration. ### norequest This option cannot be requested, regardless of user configuration. ### optional This option is optional. Only makes sense for embedded options like the client FQDN option, where the FQDN string itself is optional. **index **The option can appear more than once and will be indexed. **array **The option data is split into a space separated array, each element 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. ### ipaddress An IPv4 address, 4 bytes. ### ip6address An IPv6 address, 16 bytes. **string **[: **length**] A NVT ASCII string of printable characters. **byte **A byte. **bitflags**: **flags** 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 po‐ sition 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 bytes. **domain **An RFC 3397 encoded string. **dname **An RFC 1035 validated string. **uri **If an array then the first two bytes are the URI length inside the option data. Oth‐ erwise, the whole option data is the URI. As a space is not allowed in the URI en‐ coding, the URIs are space separated. **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. ### Example 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. ### delayedrealm 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 matching _realm_ and _secretid_. This token is used to authenticate all other messages. **delayed **Same as above, but without a realm. ### Supported Authentication Algorithms If none specified, **hmac-md5 **is the default. ### hmac-md5 ### 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. ### monocounter Read the number in the file _/var/lib/dhcpcd/dhcpcd-rdm.monotonic_ and add one to it. ### monotime Create an NTP timestamp from the system time. ### monotonic Same as **monotime**. ## SEE ALSO [_fnmatch_(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown), [_if_nametoindex_(3)](https://www.chedong.com/phpMan.php/man/ifnametoindex/3/markdown), [_dhcpcd_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd/8/markdown), [_dhcpcd-run-hooks_(8)](https://www.chedong.com/phpMan.php/man/dhcpcd-run-hooks/8/markdown) ## AUTHORS Roy Marples <<_roy@marples.name_>> ## BUGS Please report them to Debian December 18, 2023 [_DHCPCD.CONF_(5)](https://www.chedong.com/phpMan.php/man/DHCPCD.CONF/5/markdown)