2026-02-02 For the Civic Address Types Registry , please see: http://www.iana.org/assignments/civic-address-types-registry IETF Review The Bootstrap Protocol (BOOTP) describes an IP/UDP bootstrap protocol (BOOTP) which allows a diskless client machine to discover its own IP address, the address of a server host, and the name of a file to be loaded into memory and executed. The Dynamic Host Configuration Protocol (DHCP) provides a framework for automatic configuration of IP hosts. The document "DHCP Options and BOOTP Vendor Information Extensions" describes options for DHCP, some of which can also be used with BOOTP. Additional DHCP options are described in other RFCs, as documented in this registry. 0 Pad 0 None 1 Subnet Mask 4 Subnet Mask Value 2 Time Offset 4 Time Offset in Seconds from UTC (note: deprecated by 100 and 101) 3 Router N N/4 Router addresses 4 Time Server N N/4 Timeserver addresses 5 Name Server N N/4 IEN-116 Server addresses 6 Domain Server N N/4 DNS Server addresses 7 Log Server N N/4 Logging Server addresses 8 Quotes Server N N/4 Quotes Server addresses 9 LPR Server N N/4 Printer Server addresses 10 Impress Server N N/4 Impress Server addresses 11 RLP Server N N/4 RLP Server addresses 12 Hostname N Hostname string 13 Boot File Size 2 Size of boot file in 512 byte chunks 14 Merit Dump File N Client to dump and name the file to dump it to 15 Domain Name N The DNS domain name of the client 16 Swap Server N Swap Server address 17 Root Path N Path name for root disk 18 Extension File N Path name for more BOOTP info 19 Forward On/Off 1 Enable/Disable IP Forwarding 20 SrcRte On/Off 1 Enable/Disable Source Routing 21 Policy Filter N Routing Policy Filters 22 Max DG Assembly 2 Max Datagram Reassembly Size 23 Default IP TTL 1 Default IP Time to Live 24 MTU Timeout 4 Path MTU Aging Timeout 25 MTU Plateau N Path MTU Plateau Table 26 MTU Interface 2 Interface MTU Size 27 MTU Subnet 1 All Subnets are Local 28 Broadcast Address 4 Broadcast Address 29 Mask Discovery 1 Perform Mask Discovery 30 Mask Supplier 1 Provide Mask to Others 31 Router Discovery 1 Perform Router Discovery 32 Router Request 4 Router Solicitation Address 33 Static Route N Static Routing Table 34 Trailers 1 Trailer Encapsulation 35 ARP Timeout 4 ARP Cache Timeout 36 Ethernet 1 Ethernet Encapsulation 37 Default TCP TTL 1 Default TCP Time to Live 38 Keepalive Time 4 TCP Keepalive Interval 39 Keepalive Data 1 TCP Keepalive Garbage 40 NIS Domain N NIS Domain Name 41 NIS Servers N NIS Server Addresses 42 NTP Servers N NTP Server Addresses 43 Vendor Specific N Vendor Specific Information 44 NETBIOS Name Srv N NETBIOS Name Servers 45 NETBIOS Dist Srv N NETBIOS Datagram Distribution 46 NETBIOS Node Type 1 NETBIOS Node Type 47 NETBIOS Scope N NETBIOS Scope 48 X Window Font N X Window Font Server 49 X Window Manager N X Window Display Manager 50 Address Request 4 Requested IP Address 51 Address Time 4 IP Address Lease Time 52 Overload 1 Overload "sname" or "file" 53 DHCP Msg Type 1 DHCP Message Type 54 DHCP Server Id 4 DHCP Server Identification 55 Parameter List N Parameter Request List 56 DHCP Message N DHCP Error Message 57 DHCP Max Msg Size 2 DHCP Maximum Message Size 58 Renewal Time 4 DHCP Renewal (T1) Time 59 Rebinding Time 4 DHCP Rebinding (T2) Time 60 Class Id N Class Identifier 61 Client Id N Client Identifier 62 NetWare/IP Domain N NetWare/IP Domain Name 63 NetWare/IP Option N NetWare/IP sub Options 64 NIS-Domain-Name N NIS+ v3 Client Domain Name 65 NIS-Server-Addr N NIS+ v3 Server Addresses 66 Server-Name N TFTP Server Name 67 Bootfile-Name N Boot File Name 68 Home-Agent-Addrs N Home Agent Addresses 69 SMTP-Server N Simple Mail Server Addresses 70 POP3-Server N Post Office Server Addresses 71 NNTP-Server N Network News Server Addresses 72 WWW-Server N WWW Server Addresses 73 Finger-Server N Finger Server Addresses 74 IRC-Server N Chat Server Addresses 75 StreetTalk-Server N StreetTalk Server Addresses 76 STDA-Server N ST Directory Assist. Addresses 77 User-Class N User Class Information 78 Directory Agent N directory agent information 79 Service Scope N service location agent scope 80 Rapid Commit 0 Rapid Commit 81 Client FQDN N Fully Qualified Domain Name 82 Relay Agent Information N Relay Agent Information 83 iSNS N Internet Storage Name Service 84 REMOVED/Unassigned 85 NDS Servers N Novell Directory Services 86 NDS Tree Name N Novell Directory Services 87 NDS Context N Novell Directory Services 88 BCMCS Controller Domain Name list 89 BCMCS Controller IPv4 address option 90 Authentication N Authentication 91 client-last-transaction-time option 92 associated-ip option 93 Client System N Client System Architecture 94 Client NDI N Client Network Device Interface 95 LDAP N Lightweight Directory Access Protocol 96 REMOVED/Unassigned 97 UUID/GUID N UUID/GUID-based Client Identifier 98 User-Auth N Open Group's User Authentication 99 GEOCONF_CIVIC 100 PCode N IEEE 1003.1 TZ String 101 TCode N Reference to the TZ Database 102-107 REMOVED/Unassigned 108 IPv6-Only Preferred 4 Number of seconds that DHCPv4 should be disabled 109 OPTION_DHCP4O6_S46_SADDR 16 DHCPv4 over DHCPv6 Softwire Source Address Option 110 REMOVED/Unassigned 111 Unassigned 112 Netinfo Address N NetInfo Parent Server Address 113 Netinfo Tag N NetInfo Parent Server Tag 114 DHCP Captive-Portal N DHCP Captive-Portal 115 REMOVED/Unassigned 116 Auto-Config N DHCP Auto-Configuration 117 Name Service Search N Name Service Search 118 Subnet Selection Option 4 Subnet Selection Option 119 Domain Search N DNS domain search list 120 SIP Servers DHCP Option N SIP Servers DHCP Option 121 Classless Static Route Option N Classless Static Route Option 122 CCC N CableLabs Client Configuration 123 GeoConf Option 16 GeoConf Option 124 V-I Vendor Class Vendor-Identifying Vendor Class 125 V-I Vendor-Specific Information Vendor-Identifying Vendor-Specific Information 126 Removed/Unassigned 127 Removed/Unassigned 128 PXE - undefined (vendor specific) 128 Etherboot signature. 6 bytes: E4:45:74:68:00:00 128 DOCSIS "full security" server IP address 128 TFTP Server IP address (for IP Phone software load) 129 PXE - undefined (vendor specific) 129 Kernel options. Variable length string 129 Call Server IP address 130 PXE - undefined (vendor specific) 130 Ethernet interface. Variable length string. 130 Discrimination string (to identify vendor) 131 PXE - undefined (vendor specific) 131 Remote statistics server IP address 132 PXE - undefined (vendor specific) 132 IEEE 802.1Q VLAN ID 133 PXE - undefined (vendor specific) 133 IEEE 802.1D/p Layer 2 Priority 134 PXE - undefined (vendor specific) 134 Diffserv Code Point (DSCP) for VoIP signalling and media streams 135 PXE - undefined (vendor specific) 135 HTTP Proxy for phone-specific applications 136 OPTION_PANA_AGENT 137 OPTION_V4_LOST 138 OPTION_CAPWAP_AC_V4 N CAPWAP Access Controller addresses 139 OPTION-IPv4_Address-MoS N a series of suboptions 140 OPTION-IPv4_FQDN-MoS N a series of suboptions 141 SIP UA Configuration Service Domains N List of domain names to search for SIP User Agent Configuration 142 OPTION-IPv4_Address-ANDSF N ANDSF IPv4 Address Option for DHCPv4 143 OPTION_V4_SZTP_REDIRECT N This option provides a list of URIs for SZTP bootstrap servers 144 GeoLoc 16 Geospatial Location with Uncertainty 145 FORCERENEW_NONCE_CAPABLE 1 Forcerenew Nonce Capable 146 RDNSS Selection N Information for selecting RDNSS 147 OPTION_V4_DOTS_RI N The name of the peer DOTS agent. 148 OPTION_V4_DOTS_ADDRESS N (the minimal length is 4) N/4 IPv4 addresses of peer DOTS agent(s). 149 Unassigned 150 TFTP server address 150 Etherboot 150 GRUB configuration path name 151 status-code N+1 Status code and optional N byte text message describing status. 152 base-time 4 Absolute time (seconds since Jan 1, 1970) message was sent. 153 start-time-of-state 4 Number of seconds in the past when client entered current state. 154 query-start-time 4 Absolute time (seconds since Jan 1, 1970) for beginning of query. 155 query-end-time 4 Absolute time (seconds since Jan 1, 1970) for end of query. 156 dhcp-state 1 State of IP address. 157 data-source 1 Indicates information came from local or remote server. 158 OPTION_V4_PCP_SERVER Variable; the minimum length is 5. Includes one or multiple lists of PCP server IP addresses; each list is treated as a separate PCP server. 159 OPTION_V4_PORTPARAMS 4 This option is used to configure a set of ports bound to a shared IPv4 address. 160 Unassigned Previously assigned by ; known to also be used by Polycom. 161 OPTION_MUD_URL_V4 N (variable) Manufacturer Usage Descriptions 162 OPTION_V4_DNR N Encrypted DNS Server 163-174 Unassigned 175 Etherboot (Tentatively Assigned - 2005-06-23) 176 IP Telephone (Tentatively Assigned - 2005-06-23) 177 Etherboot (Tentatively Assigned - 2005-06-23) 177 PacketCable and CableHome (replaced by 122) 178-207 Unassigned 208 PXELINUX Magic 4 magic string = F1:00:74:7E Deprecated 209 Configuration File N Configuration file 210 Path Prefix N Path Prefix Option 211 Reboot Time 4 Reboot Time 212 OPTION_6RD 18 + N OPTION_6RD with N/4 6rd BR addresses 213 OPTION_V4_ACCESS_DOMAIN N Access Network Domain Name 214-219 Unassigned 220 Subnet Allocation Option N Subnet Allocation Option 221 Virtual Subnet Selection (VSS) Option 222-223 Unassigned 224-254 Reserved (Private Use) 255 End 0 None IETF Review 1 DHCPDISCOVER 2 DHCPOFFER 3 DHCPREQUEST 4 DHCPDECLINE 5 DHCPACK 6 DHCPNAK 7 DHCPRELEASE 8 DHCPINFORM 9 DHCPFORCERENEW 10 DHCPLEASEQUERY 11 DHCPLEASEUNASSIGNED 12 DHCPLEASEUNKNOWN 13 DHCPLEASEACTIVE 14 DHCPBULKLEASEQUERY 15 DHCPLEASEQUERYDONE 16 DHCPACTIVELEASEQUERY 17 DHCPLEASEQUERYSTATUS 18 DHCPTLS Not defined 1 NWIP_DOES_NOT_EXIST 2 NWIP_EXIST_IN_OPTIONS_AREA 3 NWIP_EXIST_IN_SNAME_FILE 4 NWIP_EXIST_BUT_TOO_BIG 5 NSQ_BROADCAST 6 PREFERRED_DSS 7 NEAREST_NWIP_SERVER 8 AUTORETRIES 9 AUTORETRY_SECS 10 NWIP_1_1 11 PRIMARY_DSS 12-255 Unassigned IETF Review 1 TSP's Primary DHCP Server Address 2 TSP's Secondary DHCP Server Address 3 TSP's Provisioning Server Address 4 TSP's AS-REQ/AS-REP Backoff and Retry 5 TSP's AP-REQ/AP-REP Backoff and Retry 6 TSP's Kerberos Realm Name 7 TSP's Ticket Granting Server Utilization 8 TSP's Provisioning Timer Value 9 TSP's Security Ticket Control 10 KDC Server Address 11-255 Unassigned IETF Review 0 Success 1 UnspecFail 2 QueryTerminated 3 MalformedQuery 4 NotAllowed 5 DataMissing 6 ConnectionActive 7 CatchUpComplete 8 TLSConnectionRefused 9-255 Unassigned IETF Review 0 Reserved 1 AVAILABLE 2 ACTIVE 3 EXPIRED 4 RELEASED 5 ABANDONED 6 RESET 7 REMOTE 8 TRANSITIONING 9-255 Unassigned Standards Action 0 No known altitude 1 Altitude in meters 2 Altitude in floors 3-15 Unassigned Standards Action 0 Reserved 1 Vertical datum WGS 84 defined by EPSG CRS Code 4327 2 Vertical datum NAD83 defined by EPSG CRS Code 4269 with North American Vertical Datum of 1988 (NAVD88) 3 Vertical datum NAD83 defined by EPSG CRS Code 4269 with Mean Lower Low Water (MLLW) as associated vertical datum 4-7 Unassigned Standards Action 0 Reserved 1 Implementations utilizing uncertainty parameters for both DHCPv4 and DHCPv6 GeoLoc options 2-3 Unassigned IETF Review 0 the PacketCable Provisioning Server used by the CCD. 1 the group of all PacketCable Call Management Servers used by the CCD. 2-15 Reserved and MUST be set to 0. IETF Review 1 Agent Circuit ID Sub-option 2 Agent Remote ID Sub-option 3 Sub-option 3 is reserved and should not be assigned at this time; proprietary and incompatible usages of this sub-option value have been seen limited deployment. 4 DOCSIS Device Class Suboption 5 Link selection Sub-option 6 Subscriber-ID Suboption 7 RADIUS Attributes Sub-option 8 Authentication Suboption 9 Vendor-Specific Information Suboption 10 Relay Agent Flags 11 Server Identifier Override Suboption 12 Relay Agent Identifier Sub-option 13 Access-Technology-Type Sub-option 14 Access-Network-Name Sub-option 15 Access-Point-Name Sub-option 16 Access-Point-BSSID Sub-option 17 Operator-Identifier Sub-option 18 Operator-Realm Sub-option 19 DHCPv4 Relay Source Port Sub-Option 20-150 Unassigned 151 DHCPv4 Virtual Subnet Selection Sub-Option 152 DHCPv4 Virtual Subnet Selection Control Sub-Option IETF Review 0 DHCPv4 Configuration Token RFC3118, Section 4 1 DHCPv4 Delayed Authentication RFC3118, Section 5 2 DHCPv6 Delayed Authentication (Obsolete) 3 DHCPv6 Reconfigure Key Authentication 4-254 Unassigned 255 Reserved IETF Review 0 Reserved 1 HMAC-SHA1 keyed hash IETF Review 0 Reserved 1 use of a monotonically increasing counter value Standards Action 0 Reserved 1 IS 2 CS 3 ES 4-254 Unassigned 255 Reserved IETF Review See the NTP Time Source Suboptions registry at IETF Review 0 Network Virtual Terminal (NVT) ASCII VPN identifier 1 RFC2685 VPN-ID 2-253 Unassigned 254 All VPNs (wildcard) 255 Global, default VPN Expert Review Alan DeKok, Mohamed Boucadair 1 User-Name 6 Service-Type 26 Vendor-Specific 27 Session-Timeout 88 Framed-Pool 100 Framed-IPv6-Pool 245.4 DHCPv4-Options Expert Review Alan DeKok, Mohamed Boucadair 162 OPTION_V4_DNR Ralph Droms mailto:rdroms&cisco.com 2001-01