Internet Assigned Numbers Authority

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

Last Updated
For the Civic Address Types Registry [RFC4776], please see:
Available Formats



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Registries included below

BOOTP Vendor Extensions and DHCP Options

Registration Procedure(s)
IETF Review
The Bootstrap Protocol (BOOTP) [RFC951] 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) [RFC2131] provides a framework for
automatic configuration of IP hosts.  The document "DHCP Options and
BOOTP Vendor Information Extensions" [RFC2132] 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 [RFC2132]
1 Subnet Mask 4 Subnet Mask Value [RFC2132]
2 Time Offset 4 Time Offset in Seconds from UTC (note: deprecated by 100 and 101) [RFC2132]
3 Router N N/4 Router addresses [RFC2132]
4 Time Server N N/4 Timeserver addresses [RFC2132]
5 Name Server N N/4 IEN-116 Server addresses [RFC2132]
6 Domain Server N N/4 DNS Server addresses [RFC2132]
7 Log Server N N/4 Logging Server addresses [RFC2132]
8 Quotes Server N N/4 Quotes Server addresses [RFC2132]
9 LPR Server N N/4 Printer Server addresses [RFC2132]
10 Impress Server N N/4 Impress Server addresses [RFC2132]
11 RLP Server N N/4 RLP Server addresses [RFC2132]
12 Hostname N Hostname string [RFC2132]
13 Boot File Size 2 Size of boot file in 512 byte chunks [RFC2132]
14 Merit Dump File N Client to dump and name the file to dump it to [RFC2132]
15 Domain Name N The DNS domain name of the client [RFC2132]
16 Swap Server N Swap Server address [RFC2132]
17 Root Path N Path name for root disk [RFC2132]
18 Extension File N Path name for more BOOTP info [RFC2132]
19 Forward On/Off 1 Enable/Disable IP Forwarding [RFC2132]
20 SrcRte On/Off 1 Enable/Disable Source Routing [RFC2132]
21 Policy Filter N Routing Policy Filters [RFC2132]
22 Max DG Assembly 2 Max Datagram Reassembly Size [RFC2132]
23 Default IP TTL 1 Default IP Time to Live [RFC2132]
24 MTU Timeout 4 Path MTU Aging Timeout [RFC2132]
25 MTU Plateau N Path MTU Plateau Table [RFC2132]
26 MTU Interface 2 Interface MTU Size [RFC2132]
27 MTU Subnet 1 All Subnets are Local [RFC2132]
28 Broadcast Address 4 Broadcast Address [RFC2132]
29 Mask Discovery 1 Perform Mask Discovery [RFC2132]
30 Mask Supplier 1 Provide Mask to Others [RFC2132]
31 Router Discovery 1 Perform Router Discovery [RFC2132]
32 Router Request 4 Router Solicitation Address [RFC2132]
33 Static Route N Static Routing Table [RFC2132]
34 Trailers 1 Trailer Encapsulation [RFC2132]
35 ARP Timeout 4 ARP Cache Timeout [RFC2132]
36 Ethernet 1 Ethernet Encapsulation [RFC2132]
37 Default TCP TTL 1 Default TCP Time to Live [RFC2132]
38 Keepalive Time 4 TCP Keepalive Interval [RFC2132]
39 Keepalive Data 1 TCP Keepalive Garbage [RFC2132]
40 NIS Domain N NIS Domain Name [RFC2132]
41 NIS Servers N NIS Server Addresses [RFC2132]
42 NTP Servers N NTP Server Addresses [RFC2132]
43 Vendor Specific N Vendor Specific Information [RFC2132]
44 NETBIOS Name Srv N NETBIOS Name Servers [RFC2132]
45 NETBIOS Dist Srv N NETBIOS Datagram Distribution [RFC2132]
46 NETBIOS Node Type 1 NETBIOS Node Type [RFC2132]
47 NETBIOS Scope N NETBIOS Scope [RFC2132]
48 X Window Font N X Window Font Server [RFC2132]
49 X Window Manager N X Window Display Manager [RFC2132]
50 Address Request 4 Requested IP Address [RFC2132]
51 Address Time 4 IP Address Lease Time [RFC2132]
52 Overload 1 Overload "sname" or "file" [RFC2132]
53 DHCP Msg Type 1 DHCP Message Type [RFC2132]
54 DHCP Server Id 4 DHCP Server Identification [RFC2132]
55 Parameter List N Parameter Request List [RFC2132]
56 DHCP Message N DHCP Error Message [RFC2132]
57 DHCP Max Msg Size 2 DHCP Maximum Message Size [RFC2132]
58 Renewal Time 4 DHCP Renewal (T1) Time [RFC2132]
59 Rebinding Time 4 DHCP Rebinding (T2) Time [RFC2132]
60 Class Id N Class Identifier [RFC2132]
61 Client Id N Client Identifier [RFC2132]
62 NetWare/IP Domain N NetWare/IP Domain Name [RFC2242]
63 NetWare/IP Option N NetWare/IP sub Options [RFC2242]
64 NIS-Domain-Name N NIS+ v3 Client Domain Name [RFC2132]
65 NIS-Server-Addr N NIS+ v3 Server Addresses [RFC2132]
66 Server-Name N TFTP Server Name [RFC2132]
67 Bootfile-Name N Boot File Name [RFC2132]
68 Home-Agent-Addrs N Home Agent Addresses [RFC2132]
69 SMTP-Server N Simple Mail Server Addresses [RFC2132]
70 POP3-Server N Post Office Server Addresses [RFC2132]
71 NNTP-Server N Network News Server Addresses [RFC2132]
72 WWW-Server N WWW Server Addresses [RFC2132]
73 Finger-Server N Finger Server Addresses [RFC2132]
74 IRC-Server N Chat Server Addresses [RFC2132]
75 StreetTalk-Server N StreetTalk Server Addresses [RFC2132]
76 STDA-Server N ST Directory Assist. Addresses [RFC2132]
77 User-Class N User Class Information [RFC3004]
78 Directory Agent N directory agent information [RFC2610]
79 Service Scope N service location agent scope [RFC2610]
80 Rapid Commit 0 Rapid Commit [RFC4039]
81 Client FQDN N Fully Qualified Domain Name [RFC4702]
82 Relay Agent Information N Relay Agent Information [RFC3046]
83 iSNS N Internet Storage Name Service [RFC4174]
84 REMOVED/Unassigned [RFC3679]
85 NDS Servers N Novell Directory Services [RFC2241]
86 NDS Tree Name N Novell Directory Services [RFC2241]
87 NDS Context N Novell Directory Services [RFC2241]
88 BCMCS Controller Domain Name list [RFC4280]
89 BCMCS Controller IPv4 address option [RFC4280]
90 Authentication N Authentication [RFC3118]
91 client-last-transaction-time option [RFC4388]
92 associated-ip option [RFC4388]
93 Client System N Client System Architecture [RFC4578]
94 Client NDI N Client Network Device Interface [RFC4578]
95 LDAP N Lightweight Directory Access Protocol [RFC3679]
96 REMOVED/Unassigned [RFC3679]
97 UUID/GUID N UUID/GUID-based Client Identifier [RFC4578]
98 User-Auth N Open Group's User Authentication [RFC2485]
100 PCode N IEEE 1003.1 TZ String [RFC4833]
101 TCode N Reference to the TZ Database [RFC4833]
102-107 REMOVED/Unassigned [RFC3679]
108 IPv6-Only Preferred 4 Number of seconds that DHCPv4 should be disabled [RFC8925]
109 OPTION_DHCP4O6_S46_SADDR 16 DHCPv4 over DHCPv6 Softwire Source Address Option [RFC8539]
110 REMOVED/Unassigned [RFC3679]
111 Unassigned [RFC3679]
112 Netinfo Address N NetInfo Parent Server Address [RFC3679]
113 Netinfo Tag N NetInfo Parent Server Tag [RFC3679]
114 DHCP Captive-Portal N DHCP Captive-Portal [RFC8910]
115 REMOVED/Unassigned [RFC3679]
116 Auto-Config N DHCP Auto-Configuration [RFC2563]
117 Name Service Search N Name Service Search [RFC2937]
118 Subnet Selection Option 4 Subnet Selection Option [RFC3011]
119 Domain Search N DNS domain search list [RFC3397]
120 SIP Servers DHCP Option N SIP Servers DHCP Option [RFC3361]
121 Classless Static Route Option N Classless Static Route Option [RFC3442]
122 CCC N CableLabs Client Configuration [RFC3495]
123 GeoConf Option 16 GeoConf Option [RFC6225]
124 V-I Vendor Class Vendor-Identifying Vendor Class [RFC3925]
125 V-I Vendor-Specific Information Vendor-Identifying Vendor-Specific Information [RFC3925]
126 Removed/Unassigned [RFC3679]
127 Removed/Unassigned [RFC3679]
128 PXE - undefined (vendor specific) [RFC4578]
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) [RFC4578]
129 Kernel options. Variable length string
129 Call Server IP address
130 PXE - undefined (vendor specific) [RFC4578]
130 Ethernet interface. Variable length string.
130 Discrimination string (to identify vendor)
131 PXE - undefined (vendor specific) [RFC4578]
131 Remote statistics server IP address
132 PXE - undefined (vendor specific) [RFC4578]
132 IEEE 802.1Q VLAN ID
133 PXE - undefined (vendor specific) [RFC4578]
133 IEEE 802.1D/p Layer 2 Priority
134 PXE - undefined (vendor specific) [RFC4578]
134 Diffserv Code Point (DSCP) for VoIP signalling and media streams
135 PXE - undefined (vendor specific) [RFC4578]
135 HTTP Proxy for phone-specific applications
137 OPTION_V4_LOST [RFC5223]
138 OPTION_CAPWAP_AC_V4 N CAPWAP Access Controller addresses [RFC5417]
139 OPTION-IPv4_Address-MoS N a series of suboptions [RFC5678]
140 OPTION-IPv4_FQDN-MoS N a series of suboptions [RFC5678]
141 SIP UA Configuration Service Domains N List of domain names to search for SIP User Agent Configuration [RFC6011]
142 OPTION-IPv4_Address-ANDSF N ANDSF IPv4 Address Option for DHCPv4 [RFC6153]
143 OPTION_V4_SZTP_REDIRECT N This option provides a list of URIs for SZTP bootstrap servers [RFC8572]
144 GeoLoc 16 Geospatial Location with Uncertainty [RFC6225]
145 FORCERENEW_NONCE_CAPABLE 1 Forcerenew Nonce Capable [RFC6704]
146 RDNSS Selection N Information for selecting RDNSS [RFC6731]
147 OPTION_V4_DOTS_RI N The name of the peer DOTS agent. [RFC8973]
148 OPTION_V4_DOTS_ADDRESS N (the minimal length is 4) N/4 IPv4 addresses of peer DOTS agent(s). [RFC8973]
149 Unassigned [RFC3942]
150 TFTP server address [RFC5859]
150 Etherboot
150 GRUB configuration path name
151 status-code N+1 Status code and optional N byte text message describing status. [RFC6926]
152 base-time 4 Absolute time (seconds since Jan 1, 1970) message was sent. [RFC6926]
153 start-time-of-state 4 Number of seconds in the past when client entered current state. [RFC6926]
154 query-start-time 4 Absolute time (seconds since Jan 1, 1970) for beginning of query. [RFC6926]
155 query-end-time 4 Absolute time (seconds since Jan 1, 1970) for end of query. [RFC6926]
156 dhcp-state 1 State of IP address. [RFC6926]
157 data-source 1 Indicates information came from local or remote server. [RFC6926]
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. [RFC7291]
159 OPTION_V4_PORTPARAMS 4 This option is used to configure a set of ports bound to a shared IPv4 address. [RFC7618]
160 Unassigned Previously assigned by [RFC7710]; known to also be used by Polycom. [RFC7710][RFC8910]
161 OPTION_MUD_URL_V4 N (variable) Manufacturer Usage Descriptions [RFC8520]
162 OPTION_V4_DNR N Encrypted DNS Server [RFC9463]
163-174 Unassigned [RFC3942]
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 [RFC3942]
208 PXELINUX Magic 4 magic string = F1:00:74:7E [RFC5071][Deprecated]
209 Configuration File N Configuration file [RFC5071]
210 Path Prefix N Path Prefix Option [RFC5071]
211 Reboot Time 4 Reboot Time [RFC5071]
212 OPTION_6RD 18 + N OPTION_6RD with N/4 6rd BR addresses [RFC5969]
213 OPTION_V4_ACCESS_DOMAIN N Access Network Domain Name [RFC5986]
214-219 Unassigned
220 Subnet Allocation Option N Subnet Allocation Option [RFC6656]
221 Virtual Subnet Selection (VSS) Option [RFC6607]
222-223 Unassigned [RFC3942]
224-254 Reserved (Private Use)
255 End 0 None [RFC2132]

DHCP Message Type 53 Values

Registration Procedure(s)
IETF Review
Available Formats

Value Message Type Reference
18 DHCPTLS [RFC7724]

NetWare/IP Option Type 63 Sub-Option Codes

Registration Procedure(s)
Not defined
Available Formats

Value Message Type Reference
10 NWIP_1_1 [RFC2242]
12-255 Unassigned

DHCP Cablelabs Client Configuration Option Type 122 Sub-Option Codes

Registration Procedure(s)
IETF Review
Available Formats

Code Sub-Option Description Reference
1 TSP's Primary DHCP Server Address [RFC3495]
2 TSP's Secondary DHCP Server Address [RFC3495]
3 TSP's Provisioning Server Address [RFC3495]
4 TSP's AS-REQ/AS-REP Backoff and Retry [RFC3495]
5 TSP's AP-REQ/AP-REP Backoff and Retry [RFC3495]
6 TSP's Kerberos Realm Name [RFC3495]
7 TSP's Ticket Granting Server Utilization [RFC3495]
8 TSP's Provisioning Timer Value [RFC3495]
9 TSP's Security Ticket Control [RFC3594]
10 KDC Server Address [RFC3634]
11-255 Unassigned

DHCP Status Code Type 151 Values

Registration Procedure(s)
IETF Review
Available Formats

Status-Code Name Reference
0 Success [RFC6926]
1 UnspecFail [RFC6926]
2 QueryTerminated [RFC6926]
3 MalformedQuery [RFC6926]
4 NotAllowed [RFC6926]
5 DataMissing [RFC7724]
6 ConnectionActive [RFC7724]
7 CatchUpComplete [RFC7724]
8 TLSConnectionRefused [RFC7724]
9-255 Unassigned

DHCP State Type 156 Values

Registration Procedure(s)
IETF Review
Available Formats

State Name Reference
0 Reserved [RFC6926]
2 ACTIVE [RFC6926]
6 RESET [RFC6926]
7 REMOTE [RFC6926]
9-255 Unassigned

Altitude Type Registry

Registration Procedure(s)
Standards Action
Available Formats

Type Altitude Field Description Reference
0 No known altitude [RFC6225]
1 Altitude in meters [RFC6225]
2 Altitude in floors [RFC6225]
3-15 Unassigned

Datum Registry

Registration Procedure(s)
Standards Action
Available Formats

Datum Datum Field Description Reference
0 Reserved [RFC6225]
1 Vertical datum WGS 84 defined by EPSG CRS Code 4327 [RFC6225]
2 Vertical datum NAD83 defined by EPSG CRS Code 4269 with North American Vertical Datum of 1988 (NAVD88) [RFC6225]
3 Vertical datum NAD83 defined by EPSG CRS Code 4269 with Mean Lower Low Water (MLLW) as associated vertical datum [RFC6225]
4-7 Unassigned

GeoLoc Option Version Registry

Registration Procedure(s)
Standards Action
Available Formats

Version Description Reference
0 Reserved [RFC6225]
1 Implementations utilizing uncertainty parameters for both DHCPv4 and DHCPv6 GeoLoc options [RFC6225]
2-3 Unassigned

CableLabs Client Configuration Option Ticket Control Mask Bit Definitions

Registration Procedure(s)
IETF Review
Available Formats

Bit Description Reference
0 the PacketCable Provisioning Server used by the CCD. [RFC3594]
1 the group of all PacketCable Call Management Servers used by the CCD. [RFC3594]
2-15 Reserved and MUST be set to 0.

DHCP Relay Agent Sub-Option Codes

Registration Procedure(s)
IETF Review
Available Formats

Code Sub-Option Description Reference
1 Agent Circuit ID Sub-option [RFC3046]
2 Agent Remote ID Sub-option [RFC3046]
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 [RFC3256]
5 Link selection Sub-option [RFC3527]
6 Subscriber-ID Suboption [RFC3993]
7 RADIUS Attributes Sub-option [RFC4014]
8 Authentication Suboption [RFC4030]
9 Vendor-Specific Information Suboption [RFC4243]
10 Relay Agent Flags [RFC5010]
11 Server Identifier Override Suboption [RFC5107]
12 Relay Agent Identifier Sub-option [RFC6925]
13 Access-Technology-Type Sub-option [RFC7839]
14 Access-Network-Name Sub-option [RFC7839]
15 Access-Point-Name Sub-option [RFC7839]
16 Access-Point-BSSID Sub-option [RFC7839]
17 Operator-Identifier Sub-option [RFC7839]
18 Operator-Realm Sub-option [RFC7839]
19 DHCPv4 Relay Source Port Sub-Option [RFC8357]
20-150 Unassigned
151 DHCPv4 Virtual Subnet Selection Sub-Option [RFC6607]
152 DHCPv4 Virtual Subnet Selection Control Sub-Option [RFC6607]

Authentication Suboption (value 8) - Protocol identifier values

Registration Procedure(s)
IETF Review
Available Formats

Value Protocol Reference
0 DHCPv4 Configuration Token [RFC3118, Section 4]
1 DHCPv4 Delayed Authentication [RFC3118, Section 5]
2 DHCPv6 Delayed Authentication (Obsolete) [RFC8415]
3 DHCPv6 Reconfigure Key Authentication [RFC8415]
4-254 Unassigned
255 Reserved [RFC3118]

Authentication Suboption (value 8) - Algorithm identifier values

Registration Procedure(s)
IETF Review
Available Formats

Value Algorithm Reference
0 Reserved [RFC4030]
1 HMAC-SHA1 keyed hash [RFC4030]

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

Registration Procedure(s)
IETF Review
Available Formats

Value Description Reference
0 Reserved [RFC4030]
1 use of a monotonically increasing counter value [RFC4030]

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

Registration Procedure(s)
Standards Action
Available Formats

Value Name Reference
0 Reserved [RFC5678]
1 IS [RFC5678]
2 CS [RFC5678]
3 ES [RFC5678]
4-254 Unassigned
255 Reserved [RFC5678]

NTP Time Source Suboptions

Registration Procedure(s)
IETF Review
See the NTP Time Source Suboptions registry at []

VSS Type Options

Registration Procedure(s)
IETF Review
Available Formats

Type Name Reference
0 Network Virtual Terminal (NVT) ASCII VPN identifier [RFC6607]
1 RFC2685 VPN-ID [RFC2685][RFC6607]
2-253 Unassigned
254 All VPNs (wildcard) [RFC6926]
255 Global, default VPN [RFC6607]

RADIUS Attributes Permitted in RADIUS Attributes DHCP Suboption

Registration Procedure(s)
Expert Review
Alan DeKok, Mohamed Boucadair
Available Formats

Type Code Attribute Reference
1 User-Name [RFC2865]
6 Service-Type [RFC2865]
26 Vendor-Specific [RFC2865]
27 Session-Timeout [RFC2865]
88 Framed-Pool [RFC2869]
100 Framed-IPv6-Pool [RFC3162]
245.4 DHCPv4-Options [RFC9445]

DHCP Options Permitted in the RADIUS DHCPv4-Options Attribute

Registration Procedure(s)
Expert Review
Alan DeKok, Mohamed Boucadair
Available Formats

Tag Name Reference
162 OPTION_V4_DNR [RFC9445]

Contact Information

ID Name Contact URI Last Updated
[Ralph_Droms] Ralph Droms mailto:rdroms& 2001-01