Dynamic Host Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP) Parameters

Last Updated

  • 2026-02-02

Note

For the Civic Address Types Registry RFC 4776, please see: http://www.iana.org/assignments/civic-address-types-registry

Available Formats

BOOTP Vendor Extensions and DHCP Options

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 2939: Procedures and IANA Guidelines for Definition of New DHCP Options and Message Types

Note

The Bootstrap Protocol (BOOTP) RFC 951 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) RFC 2131 provides a framework for automatic configuration of IP hosts. The document "DHCP Options and BOOTP Vendor Information Extensions" RFC 2132 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.

Available Formats

Tag Name Data Length Meaning Reference
0 Pad 0 None RFC 2132
1 Subnet Mask 4 Subnet Mask Value RFC 2132
2 Time Offset 4 Time Offset in Seconds from UTC (note: deprecated by 100 and 101) RFC 2132
3 Router N N/4 Router addresses RFC 2132
4 Time Server N N/4 Timeserver addresses RFC 2132
5 Name Server N N/4 IEN-116 Server addresses RFC 2132
6 Domain Server N N/4 DNS Server addresses RFC 2132
7 Log Server N N/4 Logging Server addresses RFC 2132
8 Quotes Server N N/4 Quotes Server addresses RFC 2132
9 LPR Server N N/4 Printer Server addresses RFC 2132
10 Impress Server N N/4 Impress Server addresses RFC 2132
11 RLP Server N N/4 RLP Server addresses RFC 2132
12 Hostname N Hostname string RFC 2132
13 Boot File Size 2 Size of boot file in 512 byte chunks RFC 2132
14 Merit Dump File N Client to dump and name the file to dump it to RFC 2132
15 Domain Name N The DNS domain name of the client RFC 2132
16 Swap Server N Swap Server address RFC 2132
17 Root Path N Path name for root disk RFC 2132
18 Extension File N Path name for more BOOTP info RFC 2132
19 Forward On/Off 1 Enable/Disable IP Forwarding RFC 2132
20 SrcRte On/Off 1 Enable/Disable Source Routing RFC 2132
21 Policy Filter N Routing Policy Filters RFC 2132
22 Max DG Assembly 2 Max Datagram Reassembly Size RFC 2132
23 Default IP TTL 1 Default IP Time to Live RFC 2132
24 MTU Timeout 4 Path MTU Aging Timeout RFC 2132
25 MTU Plateau N Path MTU Plateau Table RFC 2132
26 MTU Interface 2 Interface MTU Size RFC 2132
27 MTU Subnet 1 All Subnets are Local RFC 2132
28 Broadcast Address 4 Broadcast Address RFC 2132
29 Mask Discovery 1 Perform Mask Discovery RFC 2132
30 Mask Supplier 1 Provide Mask to Others RFC 2132
31 Router Discovery 1 Perform Router Discovery RFC 2132
32 Router Request 4 Router Solicitation Address RFC 2132
33 Static Route N Static Routing Table RFC 2132
34 Trailers 1 Trailer Encapsulation RFC 2132
35 ARP Timeout 4 ARP Cache Timeout RFC 2132
36 Ethernet 1 Ethernet Encapsulation RFC 2132
37 Default TCP TTL 1 Default TCP Time to Live RFC 2132
38 Keepalive Time 4 TCP Keepalive Interval RFC 2132
39 Keepalive Data 1 TCP Keepalive Garbage RFC 2132
40 NIS Domain N NIS Domain Name RFC 2132
41 NIS Servers N NIS Server Addresses RFC 2132
42 NTP Servers N NTP Server Addresses RFC 2132
43 Vendor Specific N Vendor Specific Information RFC 2132
44 NETBIOS Name Srv N NETBIOS Name Servers RFC 2132
45 NETBIOS Dist Srv N NETBIOS Datagram Distribution RFC 2132
46 NETBIOS Node Type 1 NETBIOS Node Type RFC 2132
47 NETBIOS Scope N NETBIOS Scope RFC 2132
48 X Window Font N X Window Font Server RFC 2132
49 X Window Manager N X Window Display Manager RFC 2132
50 Address Request 4 Requested IP Address RFC 2132
51 Address Time 4 IP Address Lease Time RFC 2132
52 Overload 1 Overload "sname" or "file" RFC 2132
53 DHCP Msg Type 1 DHCP Message Type RFC 2132
54 DHCP Server Id 4 DHCP Server Identification RFC 2132
55 Parameter List N Parameter Request List RFC 2132
56 DHCP Message N DHCP Error Message RFC 2132
57 DHCP Max Msg Size 2 DHCP Maximum Message Size RFC 2132
58 Renewal Time 4 DHCP Renewal (T1) Time RFC 2132
59 Rebinding Time 4 DHCP Rebinding (T2) Time RFC 2132
60 Class Id N Class Identifier RFC 2132
61 Client Id N Client Identifier RFC 2132
62 NetWare/IP Domain N NetWare/IP Domain Name RFC 2242
63 NetWare/IP Option N NetWare/IP sub Options RFC 2242
64 NIS-Domain-Name N NIS+ v3 Client Domain Name RFC 2132
65 NIS-Server-Addr N NIS+ v3 Server Addresses RFC 2132
66 Server-Name N TFTP Server Name RFC 2132
67 Bootfile-Name N Boot File Name RFC 2132
68 Home-Agent-Addrs N Home Agent Addresses RFC 2132
69 SMTP-Server N Simple Mail Server Addresses RFC 2132
70 POP3-Server N Post Office Server Addresses RFC 2132
71 NNTP-Server N Network News Server Addresses RFC 2132
72 WWW-Server N WWW Server Addresses RFC 2132
73 Finger-Server N Finger Server Addresses RFC 2132
74 IRC-Server N Chat Server Addresses RFC 2132
75 StreetTalk-Server N StreetTalk Server Addresses RFC 2132
76 STDA-Server N ST Directory Assist. Addresses RFC 2132
77 User-Class N User Class Information RFC 3004
78 Directory Agent N directory agent information RFC 2610
79 Service Scope N service location agent scope RFC 2610
80 Rapid Commit 0 Rapid Commit RFC 4039
81 Client FQDN N Fully Qualified Domain Name RFC 4702
82 Relay Agent Information N Relay Agent Information RFC 3046
83 iSNS N Internet Storage Name Service RFC 4174
84 REMOVED/Unassigned RFC 3679
85 NDS Servers N Novell Directory Services RFC 2241
86 NDS Tree Name N Novell Directory Services RFC 2241
87 NDS Context N Novell Directory Services RFC 2241
88 BCMCS Controller Domain Name list RFC 4280
89 BCMCS Controller IPv4 address option RFC 4280
90 Authentication N Authentication RFC 3118
91 client-last-transaction-time option RFC 4388
92 associated-ip option RFC 4388
93 Client System N Client System Architecture RFC 4578
94 Client NDI N Client Network Device Interface RFC 4578
95 LDAP N Lightweight Directory Access Protocol RFC 3679
96 REMOVED/Unassigned RFC 3679
97 UUID/GUID N UUID/GUID-based Client Identifier RFC 4578
98 User-Auth N Open Group's User Authentication RFC 2485
99 GEOCONF_CIVIC RFC 4776
100 PCode N IEEE 1003.1 TZ String RFC 4833
101 TCode N Reference to the TZ Database RFC 4833
102-107 REMOVED/Unassigned RFC 3679
108 IPv6-Only Preferred 4 Number of seconds that DHCPv4 should be disabled RFC 8925
109 OPTION_DHCP4O6_S46_SADDR 16 DHCPv4 over DHCPv6 Softwire Source Address Option RFC 8539
110 REMOVED/Unassigned RFC 3679
111 Unassigned RFC 3679
112 Netinfo Address N NetInfo Parent Server Address RFC 3679
113 Netinfo Tag N NetInfo Parent Server Tag RFC 3679
114 DHCP Captive-Portal N DHCP Captive-Portal RFC 8910
115 REMOVED/Unassigned RFC 3679
116 Auto-Config N DHCP Auto-Configuration RFC 2563
117 Name Service Search N Name Service Search RFC 2937
118 Subnet Selection Option 4 Subnet Selection Option RFC 3011
119 Domain Search N DNS domain search list RFC 3397
120 SIP Servers DHCP Option N SIP Servers DHCP Option RFC 3361
121 Classless Static Route Option N Classless Static Route Option RFC 3442
122 CCC N CableLabs Client Configuration RFC 3495
123 GeoConf Option 16 GeoConf Option RFC 6225
124 V-I Vendor Class Vendor-Identifying Vendor Class RFC 3925
125 V-I Vendor-Specific Information Vendor-Identifying Vendor-Specific Information RFC 3925
126 Removed/Unassigned RFC 3679
127 Removed/Unassigned RFC 3679
128 PXE - undefined (vendor specific) RFC 4578
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) RFC 4578
129 Kernel options. Variable length string
129 Call Server IP address
130 PXE - undefined (vendor specific) RFC 4578
130 Ethernet interface. Variable length string.
130 Discrimination string (to identify vendor)
131 PXE - undefined (vendor specific) RFC 4578
131 Remote statistics server IP address
132 PXE - undefined (vendor specific) RFC 4578
132 IEEE 802.1Q VLAN ID
133 PXE - undefined (vendor specific) RFC 4578
133 IEEE 802.1D/p Layer 2 Priority
134 PXE - undefined (vendor specific) RFC 4578
134 Diffserv Code Point (DSCP) for VoIP signalling and media streams
135 PXE - undefined (vendor specific) RFC 4578
135 HTTP Proxy for phone-specific applications
136 OPTION_PANA_AGENT RFC 5192
137 OPTION_V4_LOST RFC 5223
138 OPTION_CAPWAP_AC_V4 N CAPWAP Access Controller addresses RFC 5417
139 OPTION-IPv4_Address-MoS N a series of suboptions RFC 5678
140 OPTION-IPv4_FQDN-MoS N a series of suboptions RFC 5678
141 SIP UA Configuration Service Domains N List of domain names to search for SIP User Agent Configuration RFC 6011
142 OPTION-IPv4_Address-ANDSF N ANDSF IPv4 Address Option for DHCPv4 RFC 6153
143 OPTION_V4_SZTP_REDIRECT N This option provides a list of URIs for SZTP bootstrap servers RFC 8572
144 GeoLoc 16 Geospatial Location with Uncertainty RFC 6225
145 FORCERENEW_NONCE_CAPABLE 1 Forcerenew Nonce Capable RFC 6704
146 RDNSS Selection N Information for selecting RDNSS RFC 6731
147 OPTION_V4_DOTS_RI N The name of the peer DOTS agent. RFC 8973
148 OPTION_V4_DOTS_ADDRESS N (the minimal length is 4) N/4 IPv4 addresses of peer DOTS agent(s). RFC 8973
149 Unassigned RFC 3942
150 TFTP server address RFC 5859
150 Etherboot
150 GRUB configuration path name
151 status-code N+1 Status code and optional N byte text message describing status. RFC 6926
152 base-time 4 Absolute time (seconds since Jan 1, 1970) message was sent. RFC 6926
153 start-time-of-state 4 Number of seconds in the past when client entered current state. RFC 6926
154 query-start-time 4 Absolute time (seconds since Jan 1, 1970) for beginning of query. RFC 6926
155 query-end-time 4 Absolute time (seconds since Jan 1, 1970) for end of query. RFC 6926
156 dhcp-state 1 State of IP address. RFC 6926
157 data-source 1 Indicates information came from local or remote server. RFC 6926
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. RFC 7291
159 OPTION_V4_PORTPARAMS 4 This option is used to configure a set of ports bound to a shared IPv4 address. RFC 7618
160 Unassigned Previously assigned by RFC 7710; known to also be used by Polycom. RFC 7710; RFC 8910
161 OPTION_MUD_URL_V4 N (variable) Manufacturer Usage Descriptions RFC 8520
162 OPTION_V4_DNR N Encrypted DNS Server RFC 9463
163-174 Unassigned RFC 3942
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 RFC 3942
208 PXELINUX Magic 4 magic string = F1:00:74:7E RFC 5071; Deprecated
209 Configuration File N Configuration file RFC 5071
210 Path Prefix N Path Prefix Option RFC 5071
211 Reboot Time 4 Reboot Time RFC 5071
212 OPTION_6RD 18 + N OPTION_6RD with N/4 6rd BR addresses RFC 5969
213 OPTION_V4_ACCESS_DOMAIN N Access Network Domain Name RFC 5986
214-219 Unassigned
220 Subnet Allocation Option N Subnet Allocation Option RFC 6656
221 Virtual Subnet Selection (VSS) Option RFC 6607
222-223 Unassigned RFC 3942
224-254 Reserved (Private Use)
255 End 0 None RFC 2132

DHCP Message Type 53 Values

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 2939: Procedures and IANA Guidelines for Definition of New DHCP Options and Message Types

Available Formats

Value Message Type Reference
1 DHCPDISCOVER RFC 2132
2 DHCPOFFER RFC 2132
3 DHCPREQUEST RFC 2132
4 DHCPDECLINE RFC 2132
5 DHCPACK RFC 2132
6 DHCPNAK RFC 2132
7 DHCPRELEASE RFC 2132
8 DHCPINFORM RFC 2132
9 DHCPFORCERENEW RFC 3203
10 DHCPLEASEQUERY RFC 4388
11 DHCPLEASEUNASSIGNED RFC 4388
12 DHCPLEASEUNKNOWN RFC 4388
13 DHCPLEASEACTIVE RFC 4388
14 DHCPBULKLEASEQUERY RFC 6926
15 DHCPLEASEQUERYDONE RFC 6926
16 DHCPACTIVELEASEQUERY RFC 7724
17 DHCPLEASEQUERYSTATUS RFC 7724
18 DHCPTLS RFC 7724

NetWare/IP Option Type 63 Sub-Option Codes

Registration Procedure(s)

  • Not defined

Reference

  • RFC 2242: NetWare/IP Domain Name and Information

Available Formats

Value Message Type Reference
1 NWIP_DOES_NOT_EXIST RFC 2242
2 NWIP_EXIST_IN_OPTIONS_AREA RFC 2242
3 NWIP_EXIST_IN_SNAME_FILE RFC 2242
4 NWIP_EXIST_BUT_TOO_BIG RFC 2242
5 NSQ_BROADCAST RFC 2242
6 PREFERRED_DSS RFC 2242
7 NEAREST_NWIP_SERVER RFC 2242
8 AUTORETRIES RFC 2242
9 AUTORETRY_SECS RFC 2242
10 NWIP_1_1 RFC 2242
11 PRIMARY_DSS RFC 2242
12-255 Unassigned

DHCP Cablelabs Client Configuration Option Type 122 Sub-Option Codes

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 3495: Dynamic Host Configuration Protocol (DHCP) Option for CableLabs Client Configuration

Available Formats

Code Sub-Option Description Reference
1 TSP's Primary DHCP Server Address RFC 3495
2 TSP's Secondary DHCP Server Address RFC 3495
3 TSP's Provisioning Server Address RFC 3495
4 TSP's AS-REQ/AS-REP Backoff and Retry RFC 3495
5 TSP's AP-REQ/AP-REP Backoff and Retry RFC 3495
6 TSP's Kerberos Realm Name RFC 3495
7 TSP's Ticket Granting Server Utilization RFC 3495
8 TSP's Provisioning Timer Value RFC 3495
9 TSP's Security Ticket Control RFC 3594
10 KDC Server Address RFC 3634
11-255 Unassigned

DHCP Status Code Type 151 Values

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

Status-Code Name Reference
0 Success RFC 6926
1 UnspecFail RFC 6926
2 QueryTerminated RFC 6926
3 MalformedQuery RFC 6926
4 NotAllowed RFC 6926
5 DataMissing RFC 7724
6 ConnectionActive RFC 7724
7 CatchUpComplete RFC 7724
8 TLSConnectionRefused RFC 7724
9-255 Unassigned

DHCP State Type 156 Values

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

State Name Reference
0 Reserved RFC 6926
1 AVAILABLE RFC 6926
2 ACTIVE RFC 6926
3 EXPIRED RFC 6926
4 RELEASED RFC 6926
5 ABANDONED RFC 6926
6 RESET RFC 6926
7 REMOTE RFC 6926
8 TRANSITIONING RFC 6926
9-255 Unassigned

Altitude Type Registry

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6225: Dynamic Host Configuration Protocol Options for Coordinate-Based Location Configuration Information

Available Formats

Type Altitude Field Description Reference
0 No known altitude RFC 6225
1 Altitude in meters RFC 6225
2 Altitude in floors RFC 6225
3-15 Unassigned

Datum Registry

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6225: Dynamic Host Configuration Protocol Options for Coordinate-Based Location Configuration Information

Available Formats

Datum Datum Field Description Reference
0 Reserved RFC 6225
1 Vertical datum WGS 84 defined by EPSG CRS Code 4327 RFC 6225
2 Vertical datum NAD83 defined by EPSG CRS Code 4269 with North American Vertical Datum of 1988 (NAVD88) RFC 6225
3 Vertical datum NAD83 defined by EPSG CRS Code 4269 with Mean Lower Low Water (MLLW) as associated vertical datum RFC 6225
4-7 Unassigned

GeoLoc Option Version Registry

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 6225: Dynamic Host Configuration Protocol Options for Coordinate-Based Location Configuration Information

Available Formats

Version Description Reference
0 Reserved RFC 6225
1 Implementations utilizing uncertainty parameters for both DHCPv4 and DHCPv6 GeoLoc options RFC 6225
2-3 Unassigned

CableLabs Client Configuration Option Ticket Control Mask Bit Definitions

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 3594: PacketCable Security Ticket Control Sub-Option for the DHCP CableLabs Client Configuration (CCC) Option

Available Formats

Bit Description Reference
0 the PacketCable Provisioning Server used by the CCD. RFC 3594
1 the group of all PacketCable Call Management Servers used by the CCD. RFC 3594
2-15 Reserved and MUST be set to 0.

DHCP Relay Agent Sub-Option Codes

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 3046: DHCP Relay Agent Information Option

Available Formats

Code Sub-Option Description Reference
1 Agent Circuit ID Sub-option RFC 3046
2 Agent Remote ID Sub-option RFC 3046
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. Ralph Droms
4 DOCSIS Device Class Suboption RFC 3256
5 Link selection Sub-option RFC 3527
6 Subscriber-ID Suboption RFC 3993
7 RADIUS Attributes Sub-option RFC 4014
8 Authentication Suboption RFC 4030
9 Vendor-Specific Information Suboption RFC 4243
10 Relay Agent Flags RFC 5010
11 Server Identifier Override Suboption RFC 5107
12 Relay Agent Identifier Sub-option RFC 6925
13 Access-Technology-Type Sub-option RFC 7839
14 Access-Network-Name Sub-option RFC 7839
15 Access-Point-Name Sub-option RFC 7839
16 Access-Point-BSSID Sub-option RFC 7839
17 Operator-Identifier Sub-option RFC 7839
18 Operator-Realm Sub-option RFC 7839
19 DHCPv4 Relay Source Port Sub-Option RFC 8357
20-150 Unassigned
151 DHCPv4 Virtual Subnet Selection Sub-Option RFC 6607
152 DHCPv4 Virtual Subnet Selection Control Sub-Option RFC 6607

Authentication Suboption (value 8) - Protocol identifier values

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 3118: Authentication for DHCP Messages

Available Formats

Value Protocol Reference
0 DHCPv4 Configuration Token RFC 3118, Section 4
1 DHCPv4 Delayed Authentication RFC 3118, Section 5
2 DHCPv6 Delayed Authentication (Obsolete) RFC 9915
3 DHCPv6 Reconfigure Key Authentication RFC 9915
4-254 Unassigned
255 Reserved RFC 3118

Authentication Suboption (value 8) - Algorithm identifier values

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 4030: The Authentication Suboption for the Dynamic Host Configuration Protocol (DHCP) Relay Agent Option

Available Formats

Value Algorithm Reference
0 Reserved RFC 4030
1 HMAC-SHA1 keyed hash RFC 4030

Authentication Suboption (value 8) - Replay Detection Method (RDM) identifier values

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 4030: The Authentication Suboption for the Dynamic Host Configuration Protocol (DHCP) Relay Agent Option

Available Formats

Value Description Reference
0 Reserved RFC 4030
1 use of a monotonically increasing counter value RFC 4030

IEEE 802.21 Service Type (MoS DHCPv4 Address and FQDN Sub-Options)

Registration Procedure(s)

  • Standards Action

Reference

  • RFC 5678: Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for IEEE 802.21 Mobility Services (MoS) Discovery

Available Formats

Value Name Reference
0 Reserved RFC 5678
1 IS RFC 5678
2 CS RFC 5678
3 ES RFC 5678
4-254 Unassigned
255 Reserved RFC 5678

NTP Time Source Suboptions

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 5908: Network Time Protocol (NTP) Server Option for DHCPv6

Note

See the NTP Time Source Suboptions registry at Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

VSS Type Options

Registration Procedure(s)

  • IETF Review

Reference

  • RFC 6607: Virtual Subnet Selection Options for DHCPv4 and DHCPv6

Available Formats

Type Name Reference
0 Network Virtual Terminal (NVT) ASCII VPN identifier RFC 6607
1 RFC2685 VPN-ID RFC 2685; RFC 6607
2-253 Unassigned
254 All VPNs (wildcard) RFC 6926
255 Global, default VPN RFC 6607

RADIUS Attributes Permitted in RADIUS Attributes DHCP Suboption

Registration Procedure(s)

  • Expert Review

Expert(s)

  • Alan DeKok, Mohamed Boucadair

Reference

  • RFC 9445: RADIUS Extensions for DHCP-Configured Services

Available Formats

Type Code Attribute Reference
1 User-Name RFC 2865
6 Service-Type RFC 2865
26 Vendor-Specific RFC 2865
27 Session-Timeout RFC 2865
88 Framed-Pool RFC 2869
100 Framed-IPv6-Pool RFC 3162
245.4 DHCPv4-Options RFC 9445

DHCP Options Permitted in the RADIUS DHCPv4-Options Attribute

Registration Procedure(s)

  • Expert Review

Expert(s)

  • Alan DeKok, Mohamed Boucadair

Reference

  • RFC 9445: RADIUS Extensions for DHCP-Configured Services

Available Formats

Tag Name Reference
162 OPTION_V4_DNR RFC 9445

Contact Information

Name Contact URI Last Updated
Ralph Droms rdroms&cisco.com 2001-01