KEA DHCP OPTIONS REFERENCE
Search DHCPv4 options and review their option codes, grammar, example values, and purpose.
| 2 | root-path | 17 | text | Example : /home/path/dhcpd/ | Specifies the path name of the client's root filesystem. It is used by diskless or network-boot systems that mount their root filesystem from a remote server. |
| 3 | default-ip-ttl | 23 | uint8 | Range : 0-255 | Specifies the default IPv4 Time To Live (TTL) value the client should use for outgoing IP packets. It is used to standardize packet hop limits on the client. |
| 4 | default-tcp-ttl | 37 | uint8 | Range : 0-255 | Specifies the default TTL value the client should use for TCP segments. It is used to configure how many routed hops TCP traffic may traverse before expiring. |
| 5 | policy-filter | 21 | ip-address ip-address [, ip-address ip-address...] | Type : ipv4 | Provides destination/mask pairs used as IP source-routing policy filters. It is used by legacy hosts to decide which source-routed packets should be accepted or discarded. |
| 6 | domain-name | 15 | text | Example : example.com | Specifies the DNS domain name that the client should use. It is used to configure the client's local domain and support construction or resolution of hostnames. |
| 10 | resource-location-servers | 11 | ip-address | Type : ipv4 | Provides the IPv4 addresses of Resource Location Protocol servers. It is a legacy option used by clients that need to discover resource-location services automatically. |
| 11 | swap-server | 16 | ip-address | Type : ipv4 | Specifies the IPv4 address of the client's swap server. It is used by diskless or legacy systems that use remote swap storage during boot or operation. |
| 13 | time-offset | 2 | int32 | Range : -2,147,483,648 to +2,147,483,647 | Specifies the client's offset from UTC in seconds. It is used to configure local time information on systems that rely on DHCP for time-zone offset data. |
| 16 | routers | 3 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of default gateways, in preference order. It is used so clients can reach destinations outside their local subnet without manual gateway configuration. |
| 18 | domain-name-servers | 6 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of DNS recursive resolvers. It is used to give clients working DNS name resolution without manual configuration. |
| 19 | log-servers | 7 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of legacy log servers. It is used by clients that support the historic UDP logging service and need to discover those servers automatically. |
| 20 | lpr-servers | 9 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of Line Printer (LPR/LPD) servers. It is used by clients that need to discover legacy network printing services automatically. |
| 21 | impress-servers | 10 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of Imagen Impress protocol servers. It is a legacy option used by clients that require automatic discovery of Impress printing services. |
| 28 | unknown-clients | 6 | allow unknown-clients; | Example : allow / deny / ignore | Controls how the DHCP server handles clients that do not match a known host reservation or other configured identity. It is used to allow, deny, or ignore unregistered clients according to the network's access policy. |
| 29 | boot-size | 13 | uint16 | Range : 0-65535 | Specifies the size of the default boot image in 512-octet blocks. It is used by diskless or network-boot clients to know the expected size of the file they will download. |
| 31 | max-dgram-reassembly | 22 | uint16 | Range : 0-65535 | Specifies the largest IP datagram size, in octets, that the client should be prepared to reassemble. It is used so hosts and routers can avoid sending fragmented traffic that exceeds the client's reassembly capability. |
| 32 | interface-mtu | 26 | uint16 | Range : 0-65535 | Specifies the Maximum Transmission Unit (MTU) the client should use on its network interface. It is used to keep packet sizes compatible with the local link and reduce fragmentation. |
| 36 | extensions-path | 18 | text | Example : path/dhcpd/ | Specifies the path to a file containing additional BOOTP/DHCP vendor extensions. It is used by legacy boot clients that obtain extra configuration from a separate extension file. |
| 44 | option-6rd | 212 | uint8 uint8 ip6-address ip-address [, ip-address ...] | uint8 Range : 0-255, Address Type : ipv6 and ipv4 | Provides parameters for IPv6 Rapid Deployment (6rd), including prefix information and border-relay IPv4 addresses. It is used by clients that obtain IPv6 connectivity across an IPv4 access network using 6rd. |
| 46 | netbios-name-servers | 44 | ip-address | Type : ipv4 | Provides the IPv4 addresses of NetBIOS Name Servers, commonly WINS servers. It is used by NetBIOS-over-TCP/IP clients for legacy Windows name registration and resolution. |
| 47 | dhcp-lease-time | 51 | uint32 | Range : 0-4,294,967,295 | Specifies, in seconds, how long the assigned IPv4 lease remains valid. It is used to control address turnover and how frequently clients must renew their leases. |
| 50 | netbios-node-type | 46 | uint8 | Range : 0-255 | Specifies the NetBIOS-over-TCP/IP node type, such as B-node, P-node, M-node, or H-node. It is used to control whether a client resolves NetBIOS names by broadcast, name server, or a combination of both. |
| 55 | vendor-encapsulated-options | 43 | string | Example : string_value | Carries vendor-specific configuration data inside DHCP option 43. It is used to deliver device- or vendor-specific settings, such as controller addresses or provisioning parameters, that are not represented by standard DHCP options. |
| 56 | nis-domain | 40 | text | Example : domain.com | Specifies the Network Information Service (NIS) domain name for the client. It is used in Unix/NIS environments so clients join the correct administrative NIS domain. |
| 58 | geoconf-civic | 99 | string | Example : string_value | Carries civic-location information such as country, city, street, or building data. It is used in location-aware services, including emergency calling and network location provisioning. |
| 60 | dhcp-max-message-size | 57 | uint16 | Range : 0-65535 | Specifies the maximum DHCP message size the client is willing to receive. It is used by the server to avoid sending replies that exceed the client's receive capability. |
| 62 | slp-service-scope | 79 | boolean text | values : true or false or on or off | Provides Service Location Protocol (SLP) scope information and whether use of the supplied scope is mandatory. It is used so SLP clients can limit service discovery to the appropriate administrative scope. |
| 64 | trailer-encapsulation | 34 | flag | values : true or false or on or off | Indicates whether the client should negotiate or use trailer encapsulation on the local network. It is a legacy link-layer option retained for compatibility with older systems. |
| 66 | ieee802-3-encapsulation | 36 | flag | values : true or false or on or off | Indicates the Ethernet encapsulation convention the client should use as defined for this DHCP option. It is used by legacy Ethernet clients that need explicit encapsulation guidance. |
| 67 | netbios-dd-server | 45 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of NetBIOS Datagram Distribution servers. It is used in legacy NetBIOS-over-TCP/IP environments for datagram distribution services. |
| 68 | ntp-servers | 42 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of Network Time Protocol (NTP) servers. It is used so clients can automatically synchronize their clocks. |
| 73 | tcp-keepalive-garbage | 39 | flag | values : true or false or on or off | Indicates whether TCP keepalive probes should include a compatibility data octet rather than being empty. It is used for interoperability with older TCP implementations. |
| 79 | all-subnets-local | 27 | flag | values : true or false or on or off | Indicates whether all subnets of the client's IP network should be treated as directly local. It is used by legacy hosts to decide whether traffic to another subnet should be sent directly or through a router. |
| 80 | domain-search | 119 | domain-list | Example : example.com,sales.example.com,eng.example.com,..,etc | Provides a DNS search-domain list that clients append to unqualified names during resolution. It is used to simplify access to hosts across one or more local DNS domains. |
| 81 | dhcp-message | 56 | text | Example : message | Carries a human-readable message from the DHCP server, typically describing an error or status condition. It is used to provide diagnostic information to clients or administrators. |
| 82 | netinfo-server-tag | 113 | text | Example : text_value | Specifies the NetInfo server tag used by legacy Apple/NeXT NetInfo clients. It is used so clients can identify the appropriate NetInfo database service. |
| 83 | nwip-suboptions | 63 | string | Example : string_data | Carries NetWare/IP-specific suboptions. It is used in legacy Novell NetWare/IP deployments to deliver protocol-specific configuration to clients. |
| 84 | pcode | 100 | text | Example : text_value | Provides a POSIX-style time-zone string. It is used to configure a client's time-zone rules in environments that use POSIX TZ notation. |
| 85 | slp-directory-agent | 78 | boolean ip-address [, ip-address... ] | values : true or false or on or off , Type : ipv4 | Provides Service Location Protocol Directory Agent addresses and a flag controlling their use. It is used so SLP clients can discover central directories for available services. |
| 86 | rdnss-selection | 146 | uint8 ip-address ip-address domain-name | Range : 0-255 , Type : ipv4 | Provides information for selecting recursive DNS servers, including preference and associated domains. It is used when clients need policy guidance for choosing among multiple DNS resolvers. |
| 87 | tcode | 101 | text | Example : text_value | Provides a time-zone database identifier such as an IANA TZDB name. It is used to configure the client's geographic time zone and daylight-saving rules. |
| 88 | uap-servers | 98 | text | Example : text_value | Provides information used to locate User Authentication Protocol services. It is used in deployments that rely on DHCP to direct clients to authentication infrastructure. |
| 89 | user-class | 77 | string | Example : string_value | Carries user-class information supplied by or assigned to a DHCP client. It is used for classification and policy so servers can return different options or addresses to different client groups. |
| 104 | remote-id | 2 | string | Example : string_id_value | Carries an identifier inserted by a DHCP relay to identify the remote subscriber, circuit endpoint, or access device. It is used for subscriber-aware address assignment, auditing, and policy enforcement across relayed DHCP traffic. |
| 108 | router-solicitation-address | 32 | ip-address | Type : ipv4 | Specifies the IPv4 destination address a client should use for ICMP Router Solicitation messages. It is used by hosts performing IPv4 router discovery. |
| 109 | path-mtu-aging-timeout | 24 | uint32 | Range : 0-4,294,967,295 | Specifies how long, in seconds, a client should retain learned Path MTU information before aging it out. It is used to ensure stale path-MTU values are eventually re-evaluated. |
| 110 | arp-cache-timeout | 35 | uint32 | Range : 0-4,294,967,295 | Specifies the timeout, in seconds, for entries in the client's ARP cache. It is used to control how long IPv4-to-MAC mappings are retained before being refreshed. |
| 111 | tcp-keepalive-interval | 38 | uint32 | Range : 0-4,294,967,295 | Specifies the interval, in seconds, before TCP keepalive probes are sent on idle connections. It is used to tune detection of dead peers and long-idle TCP sessions. |
| 123 | path-mtu-plateau-table | 25 | uint16 [, uint6... ] | Range : 0-65535 | Provides a list of common MTU values that a client may use while performing Path MTU Discovery. It is used as fallback guidance when the exact path MTU cannot be learned directly. |
| 125 | cookie-servers | 8 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of Quote-of-the-Day/Cookie servers. It is a legacy discovery option for clients that use the historic cookie service. |
| 131 | time-servers | 4 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of RFC 868 Time Protocol servers. It is a legacy time-synchronization option; modern deployments generally use NTP instead. |
| 132 | nis-servers | 41 | ip-address [, ip-address... ] | Type : ipv4 | Provides the IPv4 addresses of Network Information Service (NIS) servers. It is used by Unix/NIS clients to discover directory and account-information servers automatically. |
| 135 | dhcp-option-overload | 52 | uint8 | Range : 0-255 | Indicates that the BOOTP 'file' and/or 'sname' fields are being reused to carry additional DHCP options. It is used when the normal DHCP option area is too small for all required parameters. |
| 137 | bcms-controller-names | 88 | domain-list | Example : example.com,domainexample.com,..,etc | Provides domain names of Broadband Network Gateway/BCMCS controller services as defined for this option. It is used by compatible clients to discover the relevant controller infrastructure by name. |
| 138 | netbios-scope | 47 | string | Example : string_value | Specifies the NetBIOS-over-TCP/IP scope identifier. It is used to partition legacy NetBIOS name and datagram traffic into separate administrative scopes. |
| 139 | tftp-server-name | 66 | text | Example : text_server_name | Specifies the host name or address text of the TFTP server a client should use. It is commonly used in PXE and other network-boot provisioning workflows. |
| 155 | merit-dump | 14 | — | Example : string_value | Specifies the path name of a file in which a client may store a core image for remote debugging. It is a legacy option used by systems that support network-based crash-dump handling. |
| 166 | capwap-ac-v4 | 138 | ip-address | Type : ipv4 | Provides the IPv4 address of CAPWAP Access Controllers. It is used by wireless access points to discover the controller that manages them. |
| 167 | broadcast-address | 28 | ip-address | Type : ipv4 | Specifies the IPv4 broadcast address for the client's subnet. It is used to ensure the client uses the correct local broadcast destination. |
| 169 | dhcp-server-identifier | 54 | ip-address | Type : ipv4 | Identifies the DHCPv4 server involved in an offer, request, or acknowledgement, normally by IPv4 address. It is used by clients to select and communicate with the intended server during lease negotiation. |
| 170 | streettalk-directory-assistance-server | 76 | ip-address | Type : ipv4 | Provides the IPv4 address of a Banyan VINES StreetTalk Directory Assistance server. It is used by legacy VINES clients for directory lookup. |
| 173 | v6-only-preferred | 108 | uint32 | Range : 0-4,294,967,295 | Specifies a period during which an IPv4-capable client should prefer operating without an IPv4 address when IPv6 connectivity is available. It is used in IPv6-mostly networks to reduce unnecessary IPv4 address consumption. |
| 191 | nntp-server | 71 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of NNTP news servers. It is a legacy service-discovery option for clients that consume network news. |
| 192 | mobile-ip-home-agent | 68 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of Mobile IP home agents. It is used by Mobile IP clients to discover the infrastructure that maintains reachability while the device roams. |
| 193 | smtp-server | 69 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of SMTP mail servers. It is a legacy DHCP discovery mechanism for clients that need outgoing mail-server information. |
| 194 | pop-server | 70 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of POP mail servers. It is a legacy DHCP discovery mechanism for clients that retrieve email through POP. |
| 196 | www-server | 72 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of web servers. It is a legacy service-discovery option for clients that were designed to obtain HTTP server locations through DHCP. |
| 205 | auto-config | 116 | uint8 | Range : 0-255 | Controls whether a client may use automatic IPv4 address configuration when no DHCP server is available. It is used to signal policy for fallback autoconfiguration behavior. |
| 207 | static-routes | 33 | ip-address ip-address [, ip-address ip-address...] | Type : ipv4 | Provides classful destination/router pairs for static IPv4 routes. It is used to install routes on clients automatically, although classless static route option 121 is preferred for modern CIDR networks. |
| 208 | nds-servers | 85 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of Novell Directory Services (NDS) servers. It is used by legacy Novell clients to discover directory infrastructure. |
| 209 | netinfo-server-address | 112 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of NetInfo servers. It is used by legacy Apple/NeXT systems to discover their NetInfo directory servers. |
| 211 | streettalk-server | 75 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of Banyan VINES StreetTalk servers. It is a legacy service-discovery option for VINES clients. |
| 212 | bcms-controller-address | 89 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of Broadcast and Multicast Service controller servers. It is used by compatible clients to discover BCMCS controller infrastructure directly by address. |
| 226 | pana-agent | 136 | ip-address | Type : ipv4 | Provides the IPv4 address of a PANA (Protocol for Carrying Authentication for Network Access) agent. It is used by PANA-capable clients to discover the authentication agent. |
| 231 | ip-forwarding | 19 | flag | values : true or false or on or off | Indicates whether the client should enable IPv4 packet forwarding. It is used to configure whether the host behaves only as an endpoint or may route packets between interfaces. |
| 239 | non-local-source-routing | 20 | flag | values : true or false or on or off | Indicates whether the client should permit forwarding of source-routed datagrams from non-local sources. It is a legacy security and routing-behavior option. |
| 240 | perform-mask-discovery | 29 | flag | values : true or false or on or off | Indicates whether the client should perform ICMP subnet-mask discovery. It is used by legacy hosts that need to learn the subnet mask through router discovery mechanisms. |
| 241 | mask-supplier | 30 | flag | values : true or false or on or off | Indicates whether the client should answer ICMP Address Mask Requests. It is a legacy host-behavior option for networks that use ICMP mask discovery. |
| 242 | router-discovery | 31 | flag | values : true or false or on or off | Indicates whether the client should perform ICMP Router Discovery. It is used by legacy IPv4 hosts to discover default routers dynamically. |
| 254 | name-service-search | 117 | uint16 [, uint6... ] | Range : 0-65535 | Provides a list of name-service types that the client should search or use, identified by numeric service codes. It is used to advertise which naming or directory services are available on the network. |
| 256 | font-servers | 48 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of X Window System font servers. It is used by legacy X clients to discover network font services. |
| 257 | x-display-manager | 49 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of X Display Manager servers. It is used by X terminals or Unix clients to discover remote graphical login services. |
| 258 | nisplus-servers | 65 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of NIS+ servers. It is used by Unix NIS+ clients to discover directory servers automatically. |
| 259 | finger-server | 73 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of Finger protocol servers. It is a legacy service-discovery option for clients that use the Finger protocol. |
| 260 | irc-server | 74 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of IRC servers. It is a legacy service-discovery option for clients that use Internet Relay Chat. |
| 261 | vendor-class-identifier | 60 | string | Example : string_value | Carries a string identifying the vendor or functional type of the DHCP client. It is used for client classification and to deliver vendor-specific options or boot parameters. |
| 279 | nds-tree-name | 86 | — | Example : string_name | Specifies the Novell Directory Services tree name. It is used by legacy Novell clients to connect to the correct NDS tree. |
| 280 | nds-context | 87 | — | Example : string_value | Specifies the initial Novell Directory Services context. It is used by legacy Novell clients to determine their default location within the NDS directory tree. |
| 290 | ddns-send-updates | — | boolean | values : true or false | Controls whether Kea sends Dynamic DNS (DDNS) update requests for leases at the configured scope. It is used to enable or suppress automatic DNS record creation and removal for DHCP clients. |
| 291 | ddns-override-no-update | — | boolean | values : true or false | Controls whether the server may perform DDNS updates even when a client requests that no DNS update be made. It is used when administrators want server-side DNS registration policy to take precedence over the client's preference. |
| 292 | ddns-override-client-update | — | boolean | values : true or false | Controls whether Kea overrides a client's request to update its own forward DNS record and performs the update on the client's behalf. It is used to centralize and standardize DHCP-driven DNS registration. |
| 293 | ddns-replace-client-name | — | never | always | when-not-present | when-present | values : never, always, when-not-present, when-present | Defines when Kea should replace the hostname or FQDN supplied by a client (for example never, always, or only when present or absent). It is used to enforce predictable naming for DDNS updates. |
| 294 | ddns-generated-prefix | — | text | Example : myhost | Specifies the prefix Kea uses when it must generate a hostname for a client. It is used to create deterministic DNS names when a usable client name is not available. |
| 295 | ddns-qualifying-suffix | — | fqdn | Example : example.com | Specifies the DNS suffix appended to an unqualified client hostname to form a fully qualified domain name. It is used to place DHCP-generated names into the intended DNS domain. |
| 296 | ddns-update-on-renew | — | boolean | values : true or false | Controls whether Kea sends a fresh DDNS update when a lease is renewed even if the DNS-related data has not otherwise changed. It is used when DNS records must be refreshed during lease renewals. |
| 297 | ddns-conflict-resolution-mode | — | check-with-dhcid | no-check-with-dhcid | check-exists-with-dhcid | no-check-without-dhcid | values : check-with-dhcid, no-check-with-dhcid, check-exists-with-dhcid, no-check-without-dhcid | Selects how Kea performs DDNS name-conflict checking, including whether DHCID records are checked or created. It is used to reduce accidental overwrites and define how name ownership is verified during DNS updates. |
| 298 | hostname-char-set | — | text | Example : [^A-Za-z0-9.-] | Defines the character pattern Kea uses to identify characters that are not acceptable in client hostnames. It is used to sanitize hostnames before they are used in DHCP/DDNS processing. |
| 299 | hostname-char-replacement | — | text | Example : x | Specifies the replacement text used for hostname characters matched by the configured hostname character set. It is used to convert invalid or undesirable client hostnames into DNS-safe names. |
| 319 | name-servers | 5 | ip-address [, ip-address... ] | Type : ipv4 | Provides IPv4 addresses of legacy IEN 116 name servers. It is retained for compatibility with old systems; modern clients normally use the DNS server option instead. |
| 320 | nwip-domain-name | 62 | text | Example : domain.com | Specifies the NetWare/IP domain name. It is used in legacy Novell NetWare/IP deployments so clients join the correct NetWare/IP administrative domain. |
| 321 | nisplus-domain-name | 64 | text | Example : domain.com | Specifies the NIS+ domain name for the client. It is used in Unix NIS+ environments to locate the correct namespace. |
| 322 | boot-file-name | 67 | text | Example : /tftpboot/pxelinux.0 | Specifies the boot file name that a network-boot client should download. It is used in PXE, diskless boot, and automated provisioning workflows. |
| 323 | client-system | 93 | uint16 [, uint16... ] | Range : 0-65535 | Carries the client's system architecture type. It is used by PXE and network-boot servers to select a boot image that matches the client's CPU or firmware architecture. |
| 324 | client-ndi | 94 | uint8 uint8 uint8 | Range : 0-255 | Carries the client's Network Device Interface (NDI) type and version. It is used in PXE/network-boot environments to select network bootstrap components compatible with the client's interface. |
| 325 | uuid-guid | 97 | uint8 string | Range : 0-255 and string | Carries a client machine identifier in UUID/GUID form. It is used by provisioning systems to identify a physical or virtual machine independently of its changing IP or MAC address. |
| 326 | v4-captive-portal | 114 | string | Example : https://example.com/portal | Provides the URI of a captive portal API or service associated with the network. It is used to tell clients where to obtain captive-portal status or complete network access requirements. |
| 327 | classless-static-route | 121 | ip-address ip-address [, ip-address ip-address... ] | Type : ipv4 | Provides CIDR destination prefixes and next-hop routers for classless static routes. It is used to install precise IPv4 routes on clients and is preferred over the older classful static-routes option. |
| 328 | cablelabs-client-conf | 122 | empty | No value (empty/container option) | Carries CableLabs client-configuration suboptions. It is used by CableLabs-compliant devices such as cable-network equipment to obtain vendor-defined provisioning information. |
| 329 | vivco-suboptions | 124 | uint32 string | Example : 0 "string_value" | Carries Vendor-Identifying Vendor Class information, including an enterprise number and vendor-class data. It is used to classify clients by vendor in a globally unambiguous way. |
| 330 | vivso-suboptions | 125 | uint32 | Range : 0-4,294,967,295 | Carries Vendor-Identifying Vendor-Specific Information associated with an enterprise number. It is used to deliver vendor-specific provisioning data without collisions between vendors. |
| 331 | v4-sztp-redirect | 143 | tuple | Example : https://sztp.example.com | Carries redirect information for Secure Zero Touch Provisioning (SZTP). It is used to direct newly deployed devices to trusted bootstrap or onboarding services. |
| 332 | v4-dnr | 162 | uint16 uint16 uint8 fqdn binary | Example : 1 0 0 resolver.example.com | Carries Discovery of Network-designated Resolvers (DNR) information for IPv4 clients, including encrypted DNS resolver parameters. It is used to advertise network-preferred secure DNS resolvers such as DoH or DoT services. |
| 333 | 4o6-interface | — | string | Example : eth0 | Specifies the interface used by Kea for DHCPv4-over-DHCPv6 processing. It is used to associate a DHCPv4 subnet with the IPv6-facing interface that transports DHCPv4o6 traffic. |
| 334 | 4o6-interface-id | — | string | Example : vlan-100 | Specifies the DHCPv6 Interface-ID used to identify the link for DHCPv4-over-DHCPv6 traffic. It is used to map encapsulated DHCPv4 requests to the correct IPv4 subnet. |
| 335 | 4o6-subnet | — | ipv6-prefix | Example : 2001:db8:1::/64 | Specifies the IPv6 subnet associated with a DHCPv4-over-DHCPv6 IPv4 subnet. It is used to match DHCPv4o6 requests arriving through the corresponding IPv6 link. |
| 336 | allocator | — | iterative | random | flq | values : iterative, random, flq | Selects Kea's IPv4/IPv6 address allocation algorithm, such as iterative, random, or Free Lease Queue (FLQ). It is used to tune address-selection behavior for performance, predictability, pool utilization, or multi-server deployments. |
| 337 | cache-max-age | — | uint32 | Range : 0-4,294,967,295 | Sets the maximum age of an existing lease that Kea may reuse from its lease cache. It is used to reduce database writes and processing while ensuring cached lease information is not reused beyond the configured age. |
| 338 | cache-threshold | — | decimal (0.0 to 1.0) | Example : 0.25 | Sets the fraction of a lease's valid lifetime during which Kea may reuse the existing lease from cache. It is used to reduce lease database updates and improve performance for repeated client requests. |
| 339 | calculate-tee-times | — | boolean | values : true or false | Controls whether Kea calculates the T1 renewal and T2 rebinding timers as percentages of the lease valid lifetime. It is used to derive renewal/rebinding times automatically instead of configuring fixed timer values. |
| 340 | client-class | — | string | Example : myclass | Associates the scope or pool with a client class so that it applies only to clients matching that class. It is used for policy-based DHCP behavior, segmentation, and differentiated address or option assignment. |
| 341 | decline-probation-period | — | uint32 | Range : 0-4,294,967,295 | Specifies how long a lease reported as unusable by a client remains in the declined state before it can be reclaimed. It is used to avoid immediately reallocating an address that may be in conflict. |
| 342 | dhcp4o6-port | — | uint16 | Range : 0-65535 | Specifies the UDP port used for DHCPv4-over-DHCPv6 communication. It is used in deployments that transport DHCPv4 messages through the DHCPv6 infrastructure. |
| 343 | echo-client-id | — | boolean | values : true or false | Controls whether the DHCPv4 server echoes the client's Client Identifier option in its response. It is used for compatibility with clients that expect their identifier to be returned. |
| 344 | interface | — | string | Example : eth0 | Specifies the network interface associated with the DHCP scope or service configuration. It is used to bind DHCP processing to the intended local interface. |
| 345 | match-client-id | — | boolean | values : true or false | Controls whether Kea uses the DHCPv4 Client Identifier as a primary key when matching leases to clients. It is used to determine whether lease identity follows the client-id or relies on the hardware address. |
| 346 | min-valid-lifetime | — | uint32 | Range : 0-4,294,967,295 | Sets the minimum valid lease lifetime Kea may assign. It is used to bound dynamically selected or client-influenced lease lifetimes so they do not become too short. |
| 347 | max-valid-lifetime | — | uint32 | Range : 0-4,294,967,295 | Sets the maximum valid lease lifetime Kea may assign. It is used to cap lease duration and prevent leases from remaining valid longer than the administrator intends. |
| 348 | next-server | — | ip-address | Type : ipv4 | Specifies the IPv4 address placed in the BOOTP/DHCP 'siaddr' next-server field. It is used for network boot workflows to tell clients which server hosts boot resources. |
| 349 | rebind-timer | — | uint32 | Range : 0-4,294,967,295 | Specifies the T2 timer, in seconds, after which a client may try to rebind with any available DHCP server. It is used to provide lease continuity when the original server cannot be reached. |
| 350 | renew-timer | — | uint32 | Range : 0-4,294,967,295 | Specifies the T1 timer, in seconds, after which a client should begin renewing its lease with the original server. It is used to control when lease renewal starts. |
| 351 | server-hostname | — | string | Example : some-name.example.org | Specifies the server host name placed in the BOOTP/DHCP server-name field. It is used by legacy or network-boot clients that consume the BOOTP header server-name value. |
| 352 | valid-lifetime | — | uint32 | Range : 0-4,294,967,295 | Specifies the normal valid lifetime of an assigned address or prefix. It is used to determine how long a DHCP lease remains usable before it expires. |
| 353 | require-client-classes | — | string [, string ... ] | Example : myclass1, myclass2 | Lists client classes that must be evaluated or satisfied for the configured scope. It is used to restrict DHCP behavior or resource assignment to clients matching required classification rules. |
| 354 | evaluate-additional-classes | — | string [, string ... ] | Example : myclass1, myclass2 | Lists additional client classes that Kea should evaluate after initial classification. It is used when option assignment or pool selection depends on classes that are not evaluated by default. |
| 355 | reservations-global | — | boolean | values : true or false | Controls whether Kea searches global host reservations. It is used to make reservations available across subnets and to tune reservation lookup behavior and performance. |
| 356 | reservations-in-subnet | — | boolean | values : true or false | Controls whether Kea searches reservations defined for the current subnet. It is used to enable subnet-scoped host reservations for fixed addresses, options, or per-host policy. |
| 357 | reservations-out-of-pool | — | boolean | values : true or false | Indicates that subnet reservations use addresses outside the dynamic allocation pools. It is used to let Kea skip some in-pool reservation checks and improve allocation performance when the deployment follows that model. |
| 358 | t1-percent | — | decimal (0.0 to 1.0) | Example : 0.5 | Specifies the fraction of the valid lease lifetime used to calculate the T1 renewal timer when automatic timer calculation is enabled. It is used to control how early clients begin renewal. |
| 359 | t2-percent | — | decimal (0.0 to 1.0) | Example : 0.875 | Specifies the fraction of the valid lease lifetime used to calculate the T2 rebinding timer when automatic timer calculation is enabled. It is used to control when clients broaden renewal attempts to other servers. |
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