DHCP Options
DHCP provides a framework for passing configuration information to hosts on a TCP/IP network.
Configuration parameters and other control information are carried in tagged data items that are stored
in the options field of the DHCP message. The data items themselves are also called options.
This appendix contains DHCP options and BOOTP vendor extensions from RFC 2132, and includes the
validation type for each option, as indicated in Table B-10 on page B-14.
This appendix also contains the standard Microsoft client options and several tables displaying the
options sorted by categories.
Option Descriptions
The following sections describe the DHCP options in detail:
• RFC 1497 Vendor Extensions, page B-1
• IP Layer Parameters Per Host, page B-3
APPENDIX
B
• IP Layer Parameters Per Interface, page B-4
• Link Layer Parameters Per Interface, page B-4
• TCP Parameters, page B-5
• Application and Service Parameters, page B-5
• DHCPv4 Extension Options, page B-8
• DHCPv6 Options, page B-10
• Microsoft Client Options, page B-13
• Options by Number, page B-14
• Options by Network Registrar Name, page B-18
• Option Validation Types, page B-24
RFC 1497 Vendor Extensions
Table B-1 on page B-2 lists the vendor extensions as defined in RFC 1497.
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B-1
Option Descriptions
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-1 RFC 1497 Vendor Extension Options
Option Name No. Length Description
Pad 0 1 octet Causes the subsequent fields to align on word boundaries.
End 255 1 octet End of valid information in the vendor field. Subsequent
octets should be filled with the Pad options.
Subnet Mask 1 4 octets Client subnet mask, as per RFC 950. If both the Subnet Mask
and the Router option are specified in a DHCP reply, the
Subnet Mask option must be first.
Time Offset 2 4 octets Offset of the client subnet, in seconds, from Universal Time
(UT). The offset is expressed as a twos-complement 32-bit
integer. A positive offset indicates a location east of the zero
meridian and a negative offset indicates a location we s t of the
zero meridian.
Router 3 4 octet minimum;
multiples of 4
Time Server 4 4 octet minimum;
multiples of 4
Name Server
Option
Domain Name
Server
5 4 octet minimum;
multiples of 4
6 4 octet minimum;
multiples of 4
List of IP addresses for routers on the client subnet. Routers
should be in order of preference.
List of RFC 868 compliant time servers available to the
client. Servers should be in order of preference.
List of IEN 116 name servers available to the client. Servers
should be in order of preference.
List of Domain Name System (STD 13, RFC 1035) name
servers available to the client. Servers should be in order of
preference.
Log Server 7 4 octet minimum;
multiples of 4
Cookie Server 8 4 octet minimum;
multiples of 4
LPR Server 9 4 octet minimum;
multiples of 4
Impress
Server
Resource
Location
10 4 octet minimum;
multiples of 4
11 4 octet minimum;
multiples of 4
Server
List of MIT-LCS UDP log servers available to the client.
Servers should be in order of preference.
List of RFC 865-compliant cookie servers available to the
client. Servers should be in order of preference.
List of RFC 1179-compliant line printer servers available to
the client. Servers should be in order of preference.
List of Imagen Impress servers available to the client. Servers
should be in order of preference.
List of RFC 887-compliant resource location servers
available to the client. Servers should be in order of
preference.
Host Name 12 1 octet minimum Name of the client. The name may or may not be qualified
with the local domain name. See RFC 1035 for the character
set restrictions.
Boot File Size 13 2 octets Number of 512-octet blocks in the default boot file.
Merit Dump
File
14 1 octet minimum Path name of a file to which the client core image should be
placed in the event the client crashes. The path is formatted
as a character string consisting of characters from the NVT
ASCII character set.
Domain Name 15 1 octet minimum Domain name that the client should use when resolving
hostnames through the Domain Name System.
Swap Server 16 4 octets IP address of the client swap server.
B-2
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-1 RFC 1497 Vendor Extension Options (continued)
Option Name No. Length Description
Root Path 17 1 octet minimum Path name that contains the client root disk. The path is
Extensions
18 1 octet minimum Uses a string to specify a file, retrievable through TFTP. The
Path
IP Layer Parameters Per Host
Table B-2 lists the options that affect the operation of the IP layer on a per-host basis.
Table B-2 IP Layer Parameters Per Host Options
Option Descriptions
formatted as a character string consisting of characters from
the NVT ASCII character set.
file contains information that can be interpreted in the same
way as the 64-octet vendor-extension field within the
BOOTP response, with these exceptions: the length of the file
is unconstrained, and all references to instances of this option
in the file are ignored.
Option Name No. Length Description
IP Forwarding
Enable/Disable
Non-Local
Source Routing
Enable/Disable
Policy Filter 21 8 octet minimum;
19 1 octet Specifies whether the client should configure its IP layer
for packet forwarding. Values: 0=disable; 1=enable
20 1 octet Specifies whether the client should configure its IP layer to
allow forwarding of datagrams with non-local source
routes. Values: 0=disable; 1=enable
Policy filters for non-local source routing. The filters
multiples of 8
consist of a list of IP addresses and masks that specify
destination/mask pairs with which to filter incoming source
routes. Any source-routed datagram whose next-hop
address does not match one of the filters should be
discarded by the client.
Maximum
Datagram
22 2 octets Maximum size datagram that the client should be prepared
to reassemble. Value: 576 minimum
Reassembly
Size
Default IP
Time-to-Live
Path MTU
Aging Timeout
Path MTU
Plateau Table
23 1 octet Default TTL that the client should use on outgoing
datagrams. Values: 1 to 255
24 4 octets Timeout (in seconds) to use when aging Path MTU values
(defined in RFC 1191).
25 2 octets minimum;
multiples of 2
Table of MTU sizes to use when performing Path MTU
Discovery as defined in RFC 1191. The table is formatted
as a list of 16-bit unsigned integers, ordered from smallest
to largest. Value: 68 minimum
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Option Descriptions
IP Layer Parameters Per Interface
Table B-3 lists the options that affect the operation of the IP layer on a per-interface basis. A client can
issue multiple requests, one per interface, to configure interfaces with their specific parameters.
Table B-3 IP Layer Parameters Per Interface Options
Option Name No. Length Description
Interface MTU 26 2 octets Maximum time to live to use on this interface.
All Subnets
Are Local
Broadcast
Address
Perform Mask
Discovery
Mask Supplier 30 1 octet Specifies whether or not the client should respond to subnet
Perform Router
Discovery
Router
Solicitation
Address
Static Route 33 8 octet minimum;
27 1 octet Specifies whether or not the client can assume that all
28 4 octets Broadcast address in use on the client subnet.
29 1 octet Specifies whether or not the client should perform subnet
31 1 octet Specifies whether or not the client should solicit routers
32 4 octets Address to which the client should transmit router
multiples of 8
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
subnets of the IP network to which the client is connected
use the same MTU as the subnet of that network to which the
client is directly connected.
Values: 1=all subnets share same MTU; 0=some
directly-connected subnets can have smaller MTUs
mask discovery using ICMP. Values: 0=disable; 1=enable
mask requests using ICMP.
Values: 0=do not respond; 1=respond
using the Router Discovery mechanism defined in RFC
1256. Values: 0=disable; 1=enable
solicitation requests.
List of static routes that the client should install in its
routing cache. If multiple routes to the same destination are
specified, they are in descending order of priority. The
routes consist of a list of IP address pairs. The first address
is the destination address, and the second address is the
router for the destination. The default route (0.0.0.0) is an
illegal destination for a static route.
Link Layer Parameters Per Interface
Table B-4 lists the options that affect the operation of the data link layer on a per-interface basis.
Table B-4 Link Layer Parameters Per Interface Options
Option Name No. Length Description
Trailer
Encapsulation
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B-4
34 1 octet Specifies whether or not the client should negotiate the use of trailers
(RFC 893) when using the ARP protocol. Values: 0=do not use; 1=use
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Table B-4 Link Layer Parameters Per Interface Options (continued)
Option Name No. Length Description
ARP Cache
Timeout
Ethernet
Encapsulation
35 4 octets Timeout in seconds for ARP cache entries.
36 1 octet Specifies whether or not the client should use Ethernet Version 2 (RFC
TCP Parameters
Table B-5 lists the options that affect the operation of the TCP layer on a per-interface basis.
Table B-5 TCP Parameter Options
Option Name No. Length Description
TCP Default
TTL
TCP Keepalive
Interval
TCP Keepalive
Garbage
37 1 octet Default TTL that the client should use when sending TCP segments.
38 4 octets Interval (in seconds) that the client TCP should wait before sending a
39 1 octet Specifies the whether or not the client should send TCP keep-alive
Option Descriptions
894) or IEEE 802.3 (RFC 1042) encapsulation if the interface is an
Ethernet.
Value: 0=use RFC 894 encapsulation; 1=use RFC 1042 encapsulation
Value: minimum 1
keepalive message on a TCP connection. The time is specified as a
32-bit unsigned integer. A value of zero indicates that the client should
not generate keepalive messages on connections unless specifically
requested by an application. Value: 32-bit unsigned; 0=do not generate
keepalive messages unless specifically requested.
messages with an octet of garbage for compatibility with older
implementations.
Values: 0=do not send; 1=send
Application and Service Parameters
Table B-6 lists some miscellaneous options used to configure miscellaneous applications and services.
Table B-6 Application and Service Parameter Options
Option Name No. Length Description
Network
Information
Service (NIS)
Domain
Network
Information
Service (NIS)
Servers
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40 1 octet minimum Name of the client NIS domain. The domain is formatted
41 4 octet minimum;
multiples of 4
as a character string consisting of characters from the NVT
ASCII character set.
List of IP addresses indicating NIS servers available to the
client. Servers should be in order of preference.
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description
Network Time
Protocol Servers
42 4 octet minimum;
multiples of 4
List of IP addresses indicating NTP servers that are
available to the client. Servers should be in order of
preference.
Vendor-Specific
Information
43 1 octet minimum This option is used by clients and servers to exchange
vendor-specific information. The information is an opaque
object of n octets, presumably interpreted by
vendor-specific code on the clients and servers. The
definition of this information is vendor specific. The
vendor is indicated in the dhcp-class-identifier option.
Servers not equipped to interpret the vendor-specific
information sent by a client must ignore it (although it can
be reported). Clients that do not receive desired
vendor-specific information should make an attempt to
operate without it, although they can do so (and announce
they are doing so) in a degraded mode.
If a vendor potentially encodes more than one item of
information in this option, then the vendor should encode
the option using encapsulated vendor-specific options as
described here.
The encapsulated vendor-specific options field should be
encoded as a sequence of code, length, and value fields of
identical syntax to the DHCP options field with these
exceptions:
• There should not be a magic cookie field in the
encapsulated vendor-specific extensions field.
NetBIOS over
TCP/IP Name
Server
NetBIOS over
TCP/IP
Datagram
Distribution
Server
44 4 octet minimum;
multiples of 4
45 4 octet minimum;
multiples of 4
• Codes other than 0 or 255 can be redefined by the
vendor within the encapsulated vendor-specific
extensions field, but should conform to the
tag-length-value syntax defined in section 2.
Code 255 (END), if present, signifies the end of the
encapsulated vendor extensions, not the end of the vendor
extensions field.
If the code 255 is not present, then the end of the enclosing
vendor-specific information field is taken as the end of the
encapsulated vendor-specific extensions field.
List of RFC 1001/1002 NBNS name servers in order of
preference.
List of RFC 1001/1002 NBDD servers in order of
preference.
B-6
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Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description
NetBIOS over
46 1 octet Allows NetBIOS over TCP/IP client, which are configured
TCP/IP Node
Type
NetBIOS over
47 1 octet minimum NetBIOS over TCP/IP scope parameter for the client as
TCP/IP Scope
X Window
System Font
48 4 octet minimum;
multiples of 4
Server
X Window
System Display
49 4 octet minimum;
multiples of 4
Manager
Network
64 1 octet minimum Name of the client NIS+ domain. The domain is formatted
Information
Service (NIS+)
Domain
Network
Information
65 4 octet minimum;
multiples of 4
Service (NIS+)
Servers
Mobile IP Home
Agent
68 0 octets
minimum;
multiples of 4;
expected, 4 octets
(single home
agent address)
Simple Mail
Transport
69 4 octet minimum;
multiples of 4
Protocol
(SMTP) Server
Post Office
Protocol (POP3)
70 4 octet minimum;
multiples of 4
Server
Network News
Transport
71 4 octet minimum;
multiples of 4
Protocol
(NNTP) Server
Wor ld Wid e We b
(WWW) Server
72 4 octet minimum;
multiples of 4
Option Descriptions
as described in RFC 1001/1002.
Values: Single hexadecimal octet that identifies the client
type:
• 0x1=B-node (broadcast node)
• 0x2=P-node (point-to-point node)
• 0x4=M-node (mixed node)
• 0x8=H-node
specified in RFC 1001/1002.
List of X Window System Font servers available to the
client. Servers should be in order of preference.
List of IP addresses of systems that are running the X
Window System Display Manager and are available to the
client. Addresses should be in order of preference.
as a character string consisting of characters from the NVT
ASCII character set.
List of IP addresses indicating NIS+ servers available to
the client. Servers should be in order of preference.
List of IP addresses indicating mobile IP home agents
available to the client. Agents should be in order of
preference.
Value: 32-bit address; 0=no home agents available
List of SMTP servers available to the client. Servers
should be in order of preference.
List of POP3 servers available to the client. Servers should
be in order of preference.
List of NNTP servers available to the client. Servers should
be in order of preference.
List of World Wide Web (WWW) servers available to the
client. Servers should be in order of preference.
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Option Descriptions
Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description
Finger Server 73 4 octet minimum;
Internet Relay
Chat Server
StreetTalk
Server
StreetTalk
Directory
Assistance
(STDA) Server
DHCPv4 Extension Options
Table B-7 lists the DHCPv4 extension options.
multiples of 4
74 4 octet minimum;
multiples of 4
75 4 octet minimum;
multiples of 4
76 4 octet minimum;
multiples of 4
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
List of Finger servers available to the client. Servers
should be in order of preference.
List of IRC servers available to the client. Servers should
be in order of preference.
List of StreetTalk servers available to the client. Servers
should be in order of preference.
List of STDA servers available to the client. Servers should
be in order of preference.
Table B-7 DHCPv4 Extensions
Option Name No. Length Description
Requested IP
Address
IP Address
Lease Time
50 4 octets Used in a client request (DHCPDISCOVER) to allow the client to
request that a particular IP address be assigned.
51 4 octets Used in a client request (DHCPDISCOVER or DHCPREQUEST)
to allow the client to request a lease time for the IP address. In a
server reply (DHCPOFFER), a DHCP server uses this option to
specify the lease time it is willing to offer.
Value: seconds, as 32-bit unsigned integer
Option Overload 52 1 octet Indicates that the DHCP sname or file fields are being overloaded
by using them to carry DHCP options. A DHCP server inserts this
option if the returned parameters will exceed the usual space
allotted for options. If this option is present, the client interprets
the specified additional fields after it concludes interpretation of
the standard option fields.
Values: 1=file field is used to hold options; 2=sname field is used
to hold options; 3=both fields are used to hold options
DHCP Message
Type
53 1 octet Used to convey the type of DHCP message. The preset value is 1
(DHCPDISCOVER). Values:
1=DHCPDISCOVER; 2=DHCPOFFER; 3=DHCPREQUEST;
4=DHCPDECLINE; 5=DHCPACK; 6=DHCPNAK;
7=DHCPRELEASE; 8=DHCPINFORM; 13=LEASEQUERY
B-8
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Table B-7 DHCPv4 Extensions (continued)
Option Name No. Length Description
Server Identifier 54 4 octets Used in DHCPOFFER and DHCPREQUEST messages, and can
Parameter
Request List
55 1 octet
minimum
Message 56 1 octet
minimum
Maximum
57 2 octets Maximum-length DHCP message that a server is willing to accept.
DHCP Message
Size
Renewal (T1)
58 4 octets Time interval from address assignment until the client transitions
Time Value
Rebinding (T2)
59 4 octets Time interval from address assignment until the client transitions
Time Value
Vendor Class
Identifier
60 1 octet
minimum
Option Descriptions
optionally be included in the DHCPACK and DHCPNAK
messages. DHCP servers include this option in the DHCPOFFER
in order to allow the client to distinguish between lease offers.
DHCP clients use the contents of the server identifier field as the
destination address for any DHCP messages unicast to the DHCP
server. DHCP clients also indicate which of several lease offers is
being accepted by including this option in a DHCPREQUEST
message. The identifier is the IP address of the selected server.
Used by a DHCP client to request values for specified
configuration parameters. The list of requested parameters is
specified as n octets, where each octet is a valid DHCP option code
as defined in this document. The client can list the options in order
of preference. The DHCP server does not have to return the options
in the requested order, but must try to insert the options in the order
that the client requested.
Used by a DHCP server to provide an error message to a DHCP
client in a DHCPNAK message in the event of a failure. A client
can use this option in a DHCPDECLINE message to indicate why
the client declined the offered parameters. The message consists of
n octets of NVT ASCII text, which the client can display on an
available output device.
The length is specified as an unsigned 16-bit integer. A client can
use the maximum DHCP message size option in
DHCPDISCOVER or DHCPREQUEST messages, but should not
use the option in DHCPDECLINE messages. Value: 576 minimum
to RENEWING state.
Value: seconds, as 32-bit unsigned integer
to REBINDING state.
Value: seconds, as 32-bit unsigned integer
Used by DHCP clients to optionally identify the vendor type and
configuration of a DHCP client. The information is a string of n
octets, interpreted by servers. Vendors can choose to define
specific vendor class identifiers to convey particular configuration
or other identification information about a client. For example, the
identifier can encode the client hardware configuration. Servers
not equipped to interpret the class-specific information sent by a
client must ignore it (although it can be reported). Servers that
respond should only use option 43 to return the vendor-specific
information to the client.
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Option Descriptions
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-7 DHCPv4 Extensions (continued)
Option Name No. Length Description
Client-Identifier 61 2 octet
minimum
Used by DHCP clients to specify their unique identifier. DHCP
servers use this value to index their database of address bindings.
This value is expected to be unique for all clients in an
administrative domain.
DHCP servers should treat identifiers as opaque objects. The client
identifier can consist of type-value pairs similar to the
htype/chaddr fields. For instance, it can consist of a hardware type
and hardware address. In this case, the type field should be one of
the ARP hardware types defined in STD2. A hardware type of 0
(zero) should be used when the value field contains an identifier
other than a hardware address (for example, a fully qualified
domain name).
For correct identification of clients, each client-identifier must be
unique among the client-identifiers used on the subnet to which the
client is attached. Vendors and system administrators are
responsible for choosing client-identifiers that meet this
requirement for uniqueness.
TFTP Server
Name
Bootfile Name 67 1 octet
Relay Agent
66 1 octet
minimum
Identifies a TFTP server when the sname field in the DHCP header
has been used for DHCP options.
Identifies a bootfile when the file field is the DHCP header that has
minimum
been used for DHCP options.
82 Identifies the DHCP relay agent information.
Information
iSNS 83 14 bytes
Identifies the Internet Storage Name Service (see RFC 4174)
minimum
BCMS
Controller
88 Variable List of Broadcast and Multicast Service (BCMS) controller
domains (see RFC 4280)
Domain
BCMS Address 89 4 octets
List of IP addresses for the BCMS controller (see RFC 4280)
minimum
Lease Query
Client Last
91 4 octets Time of the most recent access of the client sending a
DHCPLEASEQUERY (see RFC 4388).
Transaction
Time
Lease Query
Associated IP
92 4 octets
minimum
All IP addresses associated with the client specified in a particular
DHCPLEASEQUERY message (see RFC 4388).
Addresses
DHCPv6 Options
Table B-8 on page B-11 lists the DHCPv6 options, along with their defined data types. All the option
packets include at least an option length (option-len) and a variable length data field. There can also be
additional parameter settings, as described in the table. Mod in the Description column indicates that the
option is modifiable. Many of these options are described in RFC 3315.
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Table B-8 DHCPv6 Options
Network Registrar Name
(Type) No. Description (Mod=modifiable)
client-identifier
1 DUID identifying a client between a client and a server.
AT _B L OB
server-identifier
2 DUID identifying a server between a client and a server.
AT _B L OB
ia-na
AT _B L OB
3 Nontemporary Addresses option with the associated parameters and
addresses. Parameters are the unique ID, time the client contacts the
addresses in the IA to extend the lifetime, and time the client contacts
any available server to extend the lifetime of the addresses.
ia-ta
AT _B L OB
iaaddr
AT _B L OB
4 Temporary Addresses option with the associated parameters and
addresses.
5 IPv6 addresses associated with an IA_NA or IA_TA. (The IAADRR
must be encapsulated in the options field of an IA_NA or IA_TA
option.) The IAADDR option includes preferred and valid lifetime
fields, and the options field that encapsulates the options specific to
this address.
oro
AT _S H ORT
6 Option Request option (ORO) that identifies a list of options in a
message between a client and a server. A client can include this option
in a Solicit, Request, Renew, Rebind, Confirm, or Information-request
message to inform the server about options the client wants from the
server. A server can include this option in a Reconfigure message to
indicate which option updates the client should request.
preference
AT _I N T8
elapsed-time
AT _S H ORT
relay-message
7 A server sends this option to a client to affect what server the client
selects (Mod).
8 A client sends this option to a server to indicate how long the client
has been trying to complete a message exchange (Mod).
9 DHCP message in a Relay-forward or Relay-reply message.
AT _B L OB
auth
AT _B L OB
11 Authenticates the identity and contents of a DHCP message. The
parameters are the authentication protocol, the authentication
algorithm, the replay detection method (RDM), and the authentication
information.
server-unicast
AT_IP6ADDR
status-code
AT _B L OB
12 The server sends this option to a client to indicate that the client can
unicast messages to the server.
13 Returns a status indication related to the DHCP message or option in
which it appears. The parameters are the status code and status
message.
rapid-commit
14 Signals use of the two-message exchange for address assignment.
AT_ZEROSIZE
user-class
AT_TYPECNT
15 Clients use this option to identify the type or category of user or
applications it represents. A zero type count value field followed by
user data (as a blob).
vendor-class
AT_VENDOR_CLASS
16 Clients use this option to identify the vendor that manufactured the
hardware on which they are running.
Option Descriptions
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Option Descriptions
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-8 DHCPv6 Options (continued)
Network Registrar Name
(Type) No. Description (Mod=modifiable)
vendor-opts
AT_VENDOR_OPTS
17 Clients and servers use this option to exchange vendor-specific
information. The enterprise ID for the CableLabs vendor is 4491; the
suboptions for CableLabs are listed in Table C-4 on page C-7.
interface-id
AT _B L OB
reconfigure-message
AT _I N T8
18 Relay agents use this option to identify the interface on which the
client message is received.
19 The server includes this in a Reconfigure message to indicate whether
the client should respond with a Renew or Information-request
message.
reconfigure-accept
AT_ZEROSIZE
sip-servers-name
AT _D N SNA ME
sip-servers-address
20 Clients use this option to announce to the server whether the client is
willing to accept Reconfigure messages.
21 Domain names of the SIP outbound proxy servers for the client (Mod).
See RFC 3319.
22 IPv6 addresses of the SIP outbound proxy servers for the client (Mod).
AT_IP6ADDR
dns-servers
23 IPv6 addresses of DNS recursive name servers (Mod).
AT_IP6ADDR
domain-list
24 Domain names in the domain search list (Mod).
AT _D N SNA ME
ia-pd
AT _B L OB
25 IPv6 prefix delegation identity association and its associated
parameters and prefixes. Parameters are the unique ID, time the client
contacts the addresses in the IA to extend the lifetime, and time the
client contacts any available server to extend the lifetime of the
addresses.
iaprefix
AT _B L OB
26 IPv6 prefixes associated with an IA_PD. The prefix must be
encapsulated in the options field of an IA_PD option. Parameters are
the valid and preferred lifetimes, prefix length, and the prefix.
nis-servers
AT_IP6ADDR
nisp-servers
27 List of IPv6 addresses of Network Information Service (NIS) servers
available to the client (see RFC 3898) (Mod).
28 List of IPv6 addresses of NIS+ servers available to the client (Mod).
AT_IP6ADDR
nis-domain-name
29 Conveys the NIS domain name to the client (Mod).
AT _D N SNA ME
nisp-domain-name
30 Conveys the NIS+ domain name to the client (Mod).
AT _D N SNA ME
sntp-servers
AT_IP6ADDR
info-refresh-time
AT _T I ME
bcms-server-d
31 List of Simple Network Time Protocol (SNTP) servers available to the
client (see RFC 4075) (Mod).
32 Sets an upper bound for how long a client should wait before
refreshing DHCPv6 information (see RFC 4242) (Mod).
33 List of BCMS controller domains (see RFC 4280) (Mod).
AT _D N SNA ME
bcms-server-a
AT_IP6ADDR
34 List of IPv6 addresses for the Broadcast and Multicast Service
(BCMS) controller (see RFC 4280) (Mod).
B-12
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-8 DHCPv6 Options (continued)
Network Registrar Name
(Type) No. Description (Mod=modifiable)
geoconf-civic
36 DHCP civic addresses configuration (Mod).
AT _B L OB
remote-id
AT _B L OB
relay-agent-subscriber-id
AT _B L OB
client-fqdn
37 Relay agents that terminate switched or permanent circuits can add
this option to identify remote hosts (see RFC 4649) (Mod).
38 Allows assignment and activation of subscriber-specific actions (see
RFC 4580) (Mod).
39 DHCP client FQDN (Mod).
AT _B L OB
new-posix-timezone
AT _B L OB
new-tzdb-timezone
41 POSIX time zone, for example, EST5EDT4,
M3.2.0/02:00,M11.1.0/02:00.
42 POSIX time zone database name, for example, Europe/Zurich.
AT _B L OB
ero
AT _B L OB
lq-query
AT _B L OB
43 Relay agent Echo Request option to inform the server of the list of
relay agent options to echo back.
44 Used only in a LEASEQUERY message; identifies the query being
performed. The option includes the query type, link-address (or 0::0),
and options to provide data needed for the query.
client-data
AT _B L OB
clt-time
AT _T I ME
45 Encapsulates the data for a single client on a single link in a
LEASEQUERY-REPLY message.
46 Client last transaction time encapsulated in the client-data option;
identifies how long ago the server last communicated with the client
(in seconds).
lq-relay-data
AT _B L OB
lq-client-link
AT_IP6ADDR
47 Used only in a LEASEQUERY-REPLY message; provides the relay
agent data used when the client last communicated with the server.
48 Used only in a LEASEQUERY-REPLY message; identifies the links
on which the client has one or more bindings. It is used in reply to a
query when no link-address was specified and the client is found to be
on more than one link.
lost-server
AT _D N SNA ME
51 A DHCPv6 client will request a LoST server domain name in an
Options Request Option (ORO) (see RFC3315) (Mod).
This option contains a single domain name and must contain precisely
one root label.
Option Descriptions
Microsoft Client Options
Table B-9 lists the standard Microsoft client options.
Table B-9 Microsoft DHCP Client Options
Option Name No. Description
dhcp-lease-time 51 14 days
domain-name 15 A domain name such as cisco.com
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Option Tables
Table B-9 Microsoft DHCP Client Options (continued)
Option Name No. Description
domain-name-servers 6 IP address of the name servers
netbios-name-servers 44 WINS server address
netbios-node-type 46 Identifies the NetBIOS client type; note that Network Registrar displays
routers 3 IP address of the router for this subnet
Option Tables
The following tables display the DHCP options in various ways. They show the options sorted
numerically, by Network Registrar name, and by category.
DHCP options have a prescribed format and allowed values for their option parameters. Table B-10 lists
each DHCP option and parameter type (in the Validation column). The parameter formats and allowed
values come from the DHCP and Internet RFCs. All the DHCP options appear, but clients control only
some, and the CLI only others.
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
a warning if it is not present
Options by Number
Table B-10 shows the DHCPv4 options sorted by option number, and includes the validation type. (See
Table B-12 on page B-24 for details on the option validation types found in the Validation column.) A
0+ in the Comments column means a repeat count of zero or more occurrences, 1+ means one or more
occurrences, 2n means multiple occurrences in multiples of 2. Comments also indicate whether the
option includes suboptions, and, if so, how many, and whether the option is nonmodifiable (NM).
Tip For the syntax for adding more complex option data values for suboptions, see the “Adding Complex
Values for Suboptions” section on page 21-7.
Table B-10 DHCPv4 Options by Number
No. Network Registrar Name Protocol Name Validation Comments
0pad Pad AT_NOLEN NM
1 subnet-mask Subnet Mask AT_ IPA DD R
2 time-offset Time Offset AT _S T IM E Replaced by tz-
3 routers Router AT _I PA DD R 1+
4 time-servers Time Server AT _I PA DD R 1+
5 name-servers Name Server AT _I PA DD R 1+
6 domain-name-servers Domain Server AT _ IPA D DR 1+
7 log-servers Log Server AT _I PA DD R 1+
8 cookie-servers Quotes Server AT _I PA DD R 1+
options
(RFC 4833)
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments
9 lpr-servers LPR Server AT _ IPA DD R 1+
10 impress-servers Impress Server AT _ IPA DD R 1+
11 resource-location-servers RLP Server AT_ IPA DD R 1+
12 host-name Host Name AT_ NS T RI NG
13 boot-size Boot File Size AT_ SH OR T
14 merit-dump Merit Dump File AT _N S TR IN G
15 domain-name Domain Name AT _N S TR IN G
16 swap-server Swap Server AT _I PAD DR
17 root-path Root Path AT _ NS T RI NG
18 extensions-path Extension File AT _N ST RI NG
19 ip-forwarding Forward On/Off AT_BOOL
20 non-local-source-routing SrcRte On/Off AT_BOOL
21 policy-filters Policy Filter AT _I PA DD R 2n
22 max-dgram-reassembly Maximum DG
23 Default-ip-ttl Default IP TTL AT_RANGEBYTE
24 path-mtu-aging-timeout MTU Timeout AT_ TI ME
25 path-mtu-plateau-tables MTU Plateau AT_RANGESHORT 2n
26 interface-mtu MTU Interface AT_RANGESHORT
27 all-subnets-local MTU Subnet AT_BOOL
28 broadcast-address Broadcast Address AT _ IPA DD R
29 perform-mask-discovery Mask Discovery AT_BOOL
30 mask-supplier Mask Supplier AT_BOOL
31 router-discovery Router Discovery AT_BOOL
32 router-solicitation-address Router Request AT _I PA DD R
33 static-routes Static Route AT _ IPA DD R 2n
34 trailer-encapsulation Trailers AT_BOOL
35 arp-cache-timeout ARP Timeout AT _T IM E
36 ieee802.3-encapsulation Ethernet AT_BOOL
37 default-tcp-ttl Default TCP TTL AT_RANGEBYTE
38 tcp-keepalive-interval Keepalive Time AT_ TI ME
39 tcp-keepalive-garbage Keepalive Data AT_BOOL
40 nis-domain NIS Domain AT _ ST R IN G
41 nis-servers NIS Servers AT _ IPA DD R 1+
42 ntp-servers NTP Servers AT _ IPA DD R 1+
43 vendor-encapsulated-
options
Option Tables
AT _S H ORT
Assembly
Vendor Specific AT _B L OB NM
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Option Tables
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments
44 netbios-name-servers NetBIOS Name Server AT _ IPA DD R 1+
45 netbios-dd-servers NetBIOS Distribution
AT _I PA DD R 1+
Server
46 netbios-node-type NetBIOS Node Type AT_RANGEBYTE
47 netbios-scope NetBIOS Scope AT _ NS T RI NG
48 font-servers X Window Font AT _ IPA DD R 1+
49 x-display-managers X Window Manager AT _I PA DD R 1+
50 dhcp-requested-address Address Request AT _ IPA DD R
51 dhcp-lease-time Address Time AT _T I ME NM
52 dhcp-option-overload Overload AT _ OV E RL OA D
53 dhcp-message-type DHCP Message Type AT_MESSAGE NM (See the
DHCP Message
Type option in
Table B-7 on
page B-8)
54 dhcp-server-identifier DHCP Server ID AT _I PA DD R
55 dhcp-parameter-request-
Parameter List AT _ IN T8 0+
list
56 dhcp-message DHCP Message AT _N ST R IN G NM
57 dhcp-max-message-size DHCP Maximum
AT _S H ORT NM
Message Size
58 dhcp-renewal-time Renewing Time AT _ TI ME NM
59 dhcp-rebinding-time Rebinding Time AT _T I ME NM
60 dhcp-class-identifier Class Identifier AT _N S TR I NG
61 dhcp-client-identifier Client Identifier AT _ BL O B
62 netwareip-domain NetWare/IP Domain AT _ NS TR IN G
63 netwareip-information NetWare/IP Option AT _B L OB
64 nis+-domain NIS Domain Name AT_ NS TR IN G
65 nis+-servers NIS Server Address AT _ IPA D DR 1+
66 tftp-server TFTP Server Name AT _ NS T RI NG
67 boot-file Bootfile Name AT _ NS T RI NG
68 mobile-ip-home-agents Mobile IP Home Agent AT _ IPA DD R 0+
69 smtp-servers SMTP Server AT _I PA D DR 1+
70 pop3-servers POP3 Server AT _I PA D DR 1+
71 nntp-servers NNTP Server AT _I PA DD R 1+
72 www-servers WWW Server AT _I PA DD R 1+
73 finger-servers Finger Server AT _I PA DD R 1+
74 irc-servers IRC Server AT_ I PAD DR 1+
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments
75 streettalk-servers StreetTalk Server AT _I PA DD R 1+
76 streettalk-directory-
assistance-servers
77 dhcp-user-class-id User Class ID AT_TYPECNT Suboptions (2)
78 slp-directory-agent Service Location
79 slp-service-scope SLP Service Scope AT _B L OB Suboptions (2)
80 rapid-commit Rapid Commit AT_ZEROSIZE
81 client-fqdn Client FQDN AT _B L OB Suboptions (4)
82 relay-agent-info Relay Agent
83 iSNS Internet Storage Name
85 nds-servers NDS Servers AT_ IPA D DR 1+
86 nds-tree NDS Tree Name AT _N S TR IN G
87 nds-context NDS Context AT _ NS T RI N G
88 bcms-servers-d BCMS Controller
89 bcms-servers-a BCMS Address AT _I PA DD R 1+
90 authentication Authentication AT _B L OB Suboptions (5)
91 client-last-transaction-
time
92 associated-ip Lease Query
93 pxe-client-arch AT _S H ORT
94 pxe-client-network-id AT _B L OB Suboptions (2)
95 ldap-url AT _N S TR IN G
97 pxe-client-machine-id AT _B L OB Suboptions (2)
98 user-auth AT _N S TR IN G
99 geoconf-civic Civic Addresses
100 tz-posix IEEE 1003.1 String AT _N S TR IN G
101 tz-database Time Zone Database AT _ NS T RI NG
112 netinfo-parent-server-addr AT _I PA DD R
113 netinfo-parent-server-tag AT _N S TR IN G
114 initial-url AT _N S TR IN G
STDA Server AT_ IPA DD R 1+
AT _B L OB Suboptions (2)
Protocol Directory
Agent
AT _B L OB For suboptions,
Information
see Tab le C- 3 on
page C-2
AT _B L OB Suboptions (7)
Service (RFC4174)
AT _D N SNA ME 1+
Domain (RFC 4280)
Lease Query Client
AT _T I ME
Last Transaction Time
AT _I PA DD R 1+
Associated IP
Addresses
AT _B L OB
Configuration
Option Tables
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Option Tables
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments
116 auto-configure Autoconfiguration AT_RANGEBYTE
117 name-service-search Name Service Search AT _ SH OR T 1+
118 subnet-selection Subnet Selection AT _ IPA DD R
119 domain-search Domain Search AT _B LO B
120 sip-servers SIP Servers AT_ B LO B Suboptions (2)
121 classless-static-route Classless Static Route AT _B L OB
122 cablelabs-client-
configuration)
CableLabs Client
Configuration
AT _B L OB Suboptions (10)
(see
cablelabs-clientconfiguration,
page C-3)
123 geo-conf GeoConf Option AT _B LO B
124 v-i-vendor-class Vendor-Identifying
AT_VENDOR_CLASS NM
Vendor Class
125 v-i-vendor-info Vendor-Identifying
Vendor-Specific Info
AT_VENDOR_OPTS See also the
cablelabs-125
suboptions in
Table C-3 on
page C-2
128 mcns-security-server -- AT _I PA DD R
161 cisco-leased-ip Cisco AT _I PAD DR
162 cisco-client-requested-
Cisco AT _N S TR IN G
host-name
163 cisco-client-last-
Cisco AT _I N T
transaction-time
185 vpn-id VPN Identifier AT _B LO B NM: Suboptions
(2)
220 subnet-alloc Subnet Allocation AT _ BL OB Suboptions (5)
221 cisco-vpn-id Cisco VPN Identifier AT_ BL OB Suboptions (2)
251 cisco-auto-configure Cisco
AT_RANGEBYTE
Autoconfiguration
255 end End AT_NOLEN NM
Options by Network Registrar Name
Table B-11 lists the DHCP options by Network Registrar name. (For each option validation type,
cross-reference it by number to Table B-10 and check the Validation column.)
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Tables
Table B-11 DHCP Options by Network Registrar Name
Network Registrar Name No. Option Name Category
all-subnets-local 27 All Subnets Are Local Interface
arp-cache-timeout 35 ARP Cache Timeout Interface
associated-ip 92 Lease Query Associated IP DHCPv4
auth 11 Authentication DHCPv6
authentication 90 Authentication --
auto-configuration 116 Auto-Configuration DHCPv4
bcms-server-a 34 BCMS Address v6 DHCPv6
bcms-servers-a 89 BCMS Address DHCPv4
bcms-server-d 33 BCMS Controller Domain v6 DHCPv6
bcms-servers-d 88 BCMS Controller Domain DHCPv4
boot-file 67 Bootfile Name BOOTP
boot-size 13 Boot File Size BOOTP
broadcast-address 28 Broadcast Address Interface
cablelabs-client-configuration 122 CableLabs Client Configuration Interface
cisco-autoconfigure 251 Cisco Autoconfiguration DHCPv4
cisco-client-last-transaction-time 163 Cisco Client Last Transaction
DHCPv4
Time
cisco-client-requested-host-name 162 Cisco Client Requested Host Name DHCPv4
cisco-leased-ip 161 Cisco Leased IP Address DHCPv4
cisco-vpn-id 221 Cisco VPN Identifier DHCPv4
classless-static-route 121 Classless Static Route DHCPv4
client-data 45 Leasequery Reply Client Data DHCPv6
client-fqdn 81 DHCP Client FQDN DHCPv4
client-fqdn 39 DHCP Client FQDN DHCPv6
client-identifier 1 Client Identifier DHCPv6
client-last-transaction-time 91 Leasequery Client Last
DHCPv4
Transaction Time
clt-time 46 Leasequery Client Last
DHCPv6
Transaction Time
cookie-servers 8 Cookie Server BOOTP
default-ip-ttl 23 Default IP Time-to-Live Host IP
default-tcp-ttl 37 TCP Default TTL Interface
dhcp-class-identifier 60 Vendor Class Identifier DHCPv4
dhcp-client-identifier 61 Client-Identifier Basic
dhcp-lease-time
51 IP Address Lease Time Lease Information,
MS DHCP Client
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Option Tables
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-11 DHCP Options by Network Registrar Name (continued)
Network Registrar Name No. Option Name Category
dhcp-max-message-size 57 Maximum DHCP
DHCPv4
Message Size
dhcp-message-type 53 DHCP Message Type DHCPv4
dhcp-message 56 Message DHCPv4
dhcp-option-overload 52 Option Overload DHCPv4
dhcp-parameter-request-list 55 Parameter Request List DHCPv4
dhcp-rebinding-time 59 Rebinding (T2)
Time Value
dhcp-renewal-time 58 Renewing (T1)
Time Value
Lease Information,
MS DHCP Client
Lease Information,
MS DHCP Client
dhcp-requested-address 50 Requested IP Address DHCPv4
dhcp-server-identifier 54 Server Identifier DHCPv4
dhcp-user-class-id 77 User Class ID DHCPv4
dns-servers 23 DNS Recursive Name Server DHCPv6
domain-list 24 Domain Search List DHCPv6
domain-name 15 Domain Name Basic, MS DHCP Client
domain-name-servers 6 Domain Name Server Basic, MS DHCP Client
domain-search 119 Domain Search DHCPv4
elapsed-time 8 Elapsed Time DHCPv6
end 255 End --
ero 43 Relay Agent Echo Request Option DHCPv6
extensions-path 18 Extensions Path BOOTP
finger-servers 73 Finger Server Servers
font-servers 48 X Window System
Servers
Font Server
geo-conf 123 GeoConf DHCPv4
geoconf-civic 99 Civic Addresses Configuration DHCPv4
geoconf-civic 36 Civic Addresses Configuration DHCPv6
host-name 12 Host Name Basic
ia-na 3 Identity Association for
DHCPv6
Nontemporary Addresses
ia-pd 25 Prefix Delegation DHCPv6
ia-ta 4 Identity Association for
DHCPv6
Temporary Addresses
iaaddr 5 IA Address DHCPv6
iaprefix 26 IA Prefix DHCPv6
ieee802.3-encapsulation 36 Ethernet Encapsulation Interface
impress-servers 10 Impress Server BOOTP
B-20
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-11 DHCP Options by Network Registrar Name (continued)
Network Registrar Name No. Option Name Category
info-refresh-time 32 Information Refresh Time DHCPv6
interface-id 18 Interface Identifier DHCPv6
interface-mtu 26 Interface MTU Interface
ip-forwarding 19 IP Forwarding
irc-servers 74 IRC Server Servers
isns 83 iSNS DHCPv4
log-servers 7 Log Server Servers
lpr-servers 9 LPR Server Servers
lq-client-link 48 Leasequery Client Link Reply DHCPv6
lq-query 44 Leasequery DHCPv6
lq-relay-data 47 Leasequery Relay Agent Reply DHCPv6
mask-supplier 30 Mask Supplier Interface
max-dgram-reassembly 22 Maximum Datagram Reassembly
mcns-security-server 128 -- Servers
merit-dump 14 Merit Dump File BOOTP
mobile-ip-home-agents 68 Mobile IP Home Agent Servers
name-servers 5 Name Server BOOTP
name-service-search 117 Name Service Search DHCPv4
nds-context 87 NDS Context NetWare Client
nds-servers 85 NDS Servers NetWare Client
nds-tree 86 NDS Tree Name NetWare Client
netbios-dd-servers 45 NetBIOS over TCP/IP
netbios-name-servers 44 NetBIOS over TCP/IP
netbios-node-type 46 NetBIOS over TCP/IP
netbios-scope 47 NetBIOS over TCP/IP
netwareip-domain 62 NetWare/IP Domain Name NetWare Client
netwareip-information 63 NetWare/IP Information NetWare Client
new-posix-timezone 41 POSIX time zone string DHCPv6
new-tzdb-timezone 42
nis+-domain 64 NIS+ Domain Servers
nis+-servers 65 Network Information Service
Host IP
Enable/Disable
Host IP
Size
WINS/NetBIOS
Datagram Distribution Server
WINS/NetBIOS,
Name Server
MS DHCP Client
WINS/NetBIOS,
Node Type
MS DHCP Client
WINS/NetBIOS,
Scope
MS DHCP Client
POSIX time zone database name DHCPv6
Servers
(NIS+) Servers
Option Tables
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B-21
Option Tables
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-11 DHCP Options by Network Registrar Name (continued)
Network Registrar Name No. Option Name Category
nis-domain 40 NIS Domain Servers
nis-domain-name 29 NIS Domain Name DHCPv6
nis-servers 41 Network Information Service
Servers
(NIS) Servers
nis-servers 27 NIS Servers DHCPv6
nisp-domain-name 30 NIS+ Domain Name DHCPv6
nisp-servers 28 NIS+ Servers DHCPv6
nntp-servers 71 NNTP Server Servers
non-local-source-routing 20 Non-Local Source Routing Host IP
ntp-servers 42 NTP Servers Servers
option-time 8 Option Time DHCPv6
oro 6 Option Request Option DHCPv6
pad 0 Pad --
path-mtu-aging-timeout 24 Path MTU Aging Timeout Host IP
path-mtu-plateau-tables 25 Path MTU Plateau Table Host IP
perform-mask-discovery 29 Perform Mask Discovery Interface
policy-filters 21 Policy Filter Host IP
pop3-servers 70 POP3 Server Servers
preference 7 Preference DHCPv6
rapid-commit 80 Rapid Commit DHCPv4
rapid-commit 14 Rapid Commit DHCPv6
reconfigure-accept 20 Reconfigure Accept DHCPv6
reconfigure-message 19 Reconfigure Message DHCPv6
relay-agent-info 82 DHCP Relay Agent
DHCPv4
Information
relay-agent-subscriber-id 38 Relay Agent Subscriber ID DHCPv6
relay-message 9 Relay Message DHCPv6
remote-id 37 Relay Agent Remote ID DHCPv6
resource-location-servers 11 Resource Location Server BOOTP
root-path 17 Root Path BOOTP
router-discovery 31 Perform Router Discovery Interface
router-solicitation-address 32 Router Solicitation Address Interface
routers 3 Router Basic, MS DHCP Client
server-identifier 2 DHCPv6 Server Identifier DHCPv6
server-unicast 12 Server Unicast DHCPv6
sip-servers 120 SIP Servers DHCPv4
sip-servers-name 21 SIP Servers Domain Name List DHCPv6
B-22
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-11 DHCP Options by Network Registrar Name (continued)
Network Registrar Name No. Option Name Category
sip-servers-address 22 SIP Servers IPv6 Address List DHCPv6
slp-directory agent 78 SLP Directory Agent DHCPv4
slp-service-scope 79 SLP Service Scope DHCPv4
smtp-servers 69 SMTP Server Servers
sntp-servers 31 SNTP Configuration DHCPv6
static-route 33 Static Route Interface
status-code 13 Status Code DHCPv6
streettalk-directoryassistance-servers
streettalk-servers 75 StreetTalk Server Servers
subnet-mask 1 Subnet Mask Basic
subnet-selection 118 Subnet Selection DHCPv4
swap-server 16 Swap Server BOOTP
tcp-keepalive-garbage 39 TCP Keepalive Garbage Interface
tcp-keepalive-interval 38 TCP Keepalive Interval Interface
tftp-server 66 TFTP Server Name Servers
time-offset 2 Time Offset BOOTP
time-servers 4 Time Server BOOTP
trailer-encapsulation 34 Trailer Encapsulation Interface
tz-database 101 TZ Database String DHCPv4
tz-posix 100 IEEE 1003.1 String DHCPv4
user-auth 98 User Authentication DHCPv4
user-class 15 User Class DHCPv6
vendor-class 16 Vendor Class DHCPv6
vendor-encapsulated-options 43 Vendor Specific Information DHCPv4
vendor-opts 17 Vendor Specific Information DHCPv6
v-i-vendor-class 124 Vendor Identifying Vendor Class DHCPv4
v-i-vendor-opts 125 Vendor Identifying Vendor
vpn-id 185 VPN Identifier DHCPv4
www-servers 72 WWW Server Servers
x-display-managers 49 X Window System
Option Tables
76 STDA Server Servers
DHCPv4
Options
Servers
Display Manager
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B-23
Option Tables
Option Validation Types
Table B-12 defines the DHCP option validation types. Note that you cannot use some of them to define
custom options.
Table B-12 Validation Types
Validation Description—Web UI Equivalent)
AT_BLOB List of binary bytes—binary
AT_BOOL Boolean—boolean
AT_DATE Bytes representing a date—date
AT_DNSNAME DNS name—DNS name
AT_INT Unsigned 32-bit integer—unsigned 32-bit
AT_INT8 8-bit integer—unsigned 8-bit
AT_INTI Unsigned 32-bit integer (Intel)—unsigned 32-bit (Intel)
AT_IPADDR 32-bit IP address—IP address
AT_IP6ADDR 32-bit IPv6 address—IPv6 address
AT_MACADDR Bytes representing a MAC address—MAC address
AT_MESSAGE Unsigned 8-bit message (not usable for custom options)
AT_NOLEN No length (used for PAD and END only)
AT_NSTRING Sequence of ASCII characters—string
AT_OVERLOAD Overload bytes (not usable for custom options)
AT_RANGEBYTE Range of bytes (not usable for custom options)
AT_RANGESHORT Range of shorts (not usable for custom options)
AT_RDNSNAME Relative DNS name—relative DNS name
AT_SHORT Unsigned 16-bit integer—unsigned 16-bit
AT_SHRTI Unsigned 16-bit integer (Intel)—unsigned 16-bit (Intel)
AT_SINT Signed 32-bit integer—signed 32-bit
AT_SINT8 8-bit integer—signed 8-bit
AT_SINTI Signed 32-bit integer (Intel)—signed 32-bit (Intel)
AT_SSHORT Signed 16-bit integer—signed 16-bit
AT_SSHRTI Signed 16-bit integer (Intel)—signed 16-bit (Intel)
AT_STIME Signed 32-bit signed integer representing time—signed time
AT_STRING Unrestricted sequence of ASCII characters—string
AT_TIME Unsigned 32-bit integer representing time—unsigned time
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
B-24
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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Table B-12 Validation Types (continued)
Validation Description—Web UI Equivalent)
AT_TYPECNT Type requiring two child definition: size of the type field, and type of
data—counted-type:
For the DHCPv4 dhcp-user-class-id option (77), the repeating pattern is:
[ len (1 byte) ] [ data, of single type ]
For the DHCPv6 user-class option (15), the repeating pattern is:
[ len (2 byte) ] [ data, of single type ]
AT_VENDOR_CLASS Vendor-class option (enterprise ID followed by opaque data; if DHCPv4,
enterprise ID is followed by EID length)—vendor-class
AT_VENDOR_OPTS Vendor-specific options data (enterprise ID followed by TLVs of
vendor-specific data; if DHCPv4, enterprise ID is followed by EID
length)—vendor-opts
AT_ZEROSIZE 32 bits of zero size (no longer used for PAD and END)
Option Tables
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Option Tables
Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
B-26
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