Classless static route option
DHCP option 121, which supplies IPv4 routes as destination prefixes and next-hop routers. When present, clients generally use it instead of the older classful static route option 33.
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Browse the glossaryDHCPv4 glossary
45 definitions associated with DHCPv4.
Browse DHCPv4 definitions
45 matching terms
Page 1 of 2DHCPACK
A server message confirming the offered or renewed IPv4 configuration. The client can enter or remain in the BOUND state after validating and applying the configuration.
Read definitionDHCPDECLINE
A client message reporting that the offered address appears to be in use. The server normally marks the address as conflicted or abandoned.
Read definitionDHCPDISCOVER
The initial client message used to locate DHCP servers and request configuration. It is often broadcast because the client does not yet have a usable IPv4 address.
Read definitionDHCPFORCERENEW
A server-initiated message asking a client to begin lease renewal so configuration can be refreshed. Authentication or trusted network controls are important because the message can otherwise be abused.
Read definitionDHCPINFORM
A message sent by a client that already has an IPv4 address but wants additional local configuration options. The server replies with DHCPACK without allocating a new address lease.
Read definitionDHCPNAK
A negative acknowledgement indicating that the client's requested or remembered IPv4 configuration is not valid for the current network or cannot be honored. The client normally returns to initial configuration.
Read definitionDHCPOFFER
A server proposal containing an available IPv4 address and configuration. A client can receive multiple offers and select one by sending DHCPREQUEST.
Read definitionDHCPRELEASE
A client message telling the server that it is voluntarily giving up its lease. Because release is not guaranteed during shutdown or disconnect, servers must still rely on lease expiration.
Read definitionDHCPREQUEST
A client message used to select an offer, confirm a remembered address, renew a lease, or rebind. Context and included options tell the server which use applies.
Read definitionDORA
A mnemonic for the common DHCPv4 address-acquisition exchange: Discover, Offer, Request, Acknowledge. Additional messages and paths exist for renewal, reboot, decline, release, and information-only operation.
Read definitionGIADDR
The gateway IP address field inserted by a DHCP relay agent. The server uses it to identify the client link and select the appropriate subnet, pool, and options.
Read definitionOption 119
The Domain Search option, which distributes an ordered list of DNS search suffixes using DNS name compression encoding. It is distinct from option 15, which carries a single domain name.
Read definitionOption 12
The Host Name option, used by a DHCPv4 client to provide a hostname string. Modern DDNS workflows often prefer the Client FQDN option because it carries a complete name and update flags.
Read definitionOption 121
The Classless Static Route option, which distributes destination prefixes and next-hop routers. It supersedes the older classful static route option for capable clients.
Read definitionOption 125
The V-I Vendor-Specific Information option, which namespaces vendor data using IANA enterprise numbers. It supports multiple vendors in a structured format.
Read definitionOption 15
The Domain Name option, used to provide a client's local DNS domain. It is not the same as the domain search list option, which can carry multiple suffixes.
Read definitionOption 150
A commonly deployed Cisco-specific option used to provide one or more TFTP server addresses to IP phones and other devices. It is not a generally assigned IETF DHCP option in the same sense as standard options.
Read definitionOption 160
A code often used by vendors for provisioning URLs or server discovery. Its meaning is not universal and must be verified for the specific client and server implementation.
Read definitionOption 161
The Manufacturer Usage Descriptions URL option for DHCPv4, allowing a device to provide a URL for its MUD policy description.
Read definitionOption 162
The DHCPv4 Discovery of Network-designated Resolvers option, used to advertise encrypted DNS resolver information to clients.
Read definitionOption 43
The Vendor-Specific Information option, whose internal format is defined by the vendor or application. It is widely used for controller discovery and provisioning.
Read definitionOption 50
The Requested IP Address option, used by a client to identify the IPv4 address it wants during selection or reboot processing.
Read definitionOption 51
The IP Address Lease Time option, carrying the requested or granted lease duration in seconds.
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