GE StoreSafe Pro Series User manual

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APPENDIX
B
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
•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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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Descriptions
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 west of the
zero meridian.
Router 3 4 octet minimum;
multiples of 4
List of IP addresses for routers on the client subnet. Routers
should be in order of preference.
Time Server 4 4 octet minimum;
multiples of 4
List of RFC 868 compliant time servers available to the
client. Servers should be in order of preference.
Name Server
Option
5 4 octet minimum;
multiples of 4
List of IEN 116 name servers available to the client. Servers
should be in order of preference.
Domain Name
Server
6 4 octet minimum;
multiples of 4
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
List of MIT-LCS UDP log servers available to the client.
Servers should be in order of preference.
Cookie Server 8 4 octet minimum;
multiples of 4
List of RFC 865-compliant cookie servers available to the
client. Servers should be in order of preference.
LPR Server 9 4 octet minimum;
multiples of 4
List of RFC 1179-compliant line printer servers available to
the client. Servers should be in order of preference.
Impress
Server
10 4 octet minimum;
multiples of 4
List of Imagen Impress servers available to the client. Servers
should be in order of preference.
Resource
Location
Server
11 4 octet minimum;
multiples of 4
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.

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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Descriptions
IP Layer Parameters Per Host
Table B-2 lists the options that affect the operation of the IP layer on a per-host basis.
Root Path 17 1 octet minimum Path name that contains the client root disk. The path is
formatted as a character string consisting of characters from
the NVT ASCII character set.
Extensions
Path
18 1 octet minimum Uses a string to specify a file, retrievable through TFTP. The
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.
Table B-1 RFC 1497 Vendor Extension Options (continued)
Option Name No. Length Description
Table B-2 IP Layer Parameters Per Host Options
Option Name No. Length Description
IP Forwarding
Enable/Disable
19 1 octet Specifies whether the client should configure its IP layer
for packet forwarding. Values: 0=disable; 1=enable
Non-Local
Source Routing
Enable/Disable
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 Filter 21 8 octet minimum;
multiples of 8
Policy filters for non-local source routing. The filters
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
Reassembly
Size
22 2 octets Maximum size datagram that the client should be prepared
to reassemble. Value: 576 minimum
Default IP
Time-to-Live
23 1 octet Default TTL that the client should use on outgoing
datagrams. Values: 1 to 255
Path MTU
Aging Timeout
24 4 octets Timeout (in seconds) to use when aging Path MTU values
(defined in RFC 1191).
Path MTU
Plateau Table
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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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
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.
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-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
27 1 octet Specifies whether or not the client can assume that all
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
Broadcast
Address
28 4 octets Broadcast address in use on the client subnet.
Perform Mask
Discovery
29 1 octet Specifies whether or not the client should perform subnet
mask discovery using ICMP. Values: 0=disable; 1=enable
Mask Supplier 30 1 octet Specifies whether or not the client should respond to subnet
mask requests using ICMP.
Values: 0=do not respond; 1=respond
Perform Router
Discovery
31 1 octet Specifies whether or not the client should solicit routers
using the Router Discovery mechanism defined in RFC
1256. Values: 0=disable; 1=enable
Router
Solicitation
Address
32 4 octets Address to which the client should transmit router
solicitation requests.
Static Route 33 8 octet minimum;
multiples of 8
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.
Table B-4 Link Layer Parameters Per Interface Options
Option Name No. Length Description
Trailer
Encapsulation
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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Option Descriptions
TCP Parameters
Table B-5 lists the options that affect the operation of the TCP layer on a per-interface basis.
Application and Service Parameters
Table B-6 lists some miscellaneous options used to configure miscellaneous applications and services.
ARP Cache
Timeout
35 4 octets Timeout in seconds for ARP cache entries.
Ethernet
Encapsulation
36 1 octet Specifies whether or not the client should use Ethernet Version 2 (RFC
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
Table B-4 Link Layer Parameters Per Interface Options (continued)
Option Name No. Length Description
Table B-5 TCP Parameter Options
Option Name No. Length Description
TCP Default
TTL
37 1 octet Default TTL that the client should use when sending TCP segments.
Value: minimum 1
TCP Keepalive
Interval
38 4 octets Interval (in seconds) that the client TCP should wait before sending a
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.
TCP Keepalive
Garbage
39 1 octet Specifies the whether or not the client should send TCP keep-alive
messages with an octet of garbage for compatibility with older
implementations.
Values: 0=do not send; 1=send
Table B-6 Application and Service Parameter Options
Option Name No. Length Description
Network
Information
Service (NIS)
Domain
40 1 octet minimum Name of the client NIS domain. The domain is formatted
as a character string consisting of characters from the NVT
ASCII character set.
Network
Information
Service (NIS)
Servers
41 4 octet minimum;
multiples of 4
List of IP addresses indicating NIS servers available to the
client. Servers should be in order of preference.

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Option Descriptions
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 noctets, 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.
•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.
NetBIOS over
TCP/IP Name
Server
44 4 octet minimum;
multiples of 4
List of RFC 1001/1002 NBNS name servers in order of
preference.
NetBIOS over
TCP/IP
Datagram
Distribution
Server
45 4 octet minimum;
multiples of 4
List of RFC 1001/1002 NBDD servers in order of
preference.
Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description

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Option Descriptions
NetBIOS over
TCP/IP Node
Type
46 1 octet Allows NetBIOS over TCP/IP client, which are configured
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
NetBIOS over
TCP/IP Scope
47 1 octet minimum NetBIOS over TCP/IP scope parameter for the client as
specified in RFC 1001/1002.
X Window
System Font
Server
48 4 octet minimum;
multiples of 4
List of X Window System Font servers available to the
client. Servers should be in order of preference.
X Window
System Display
Manager
49 4 octet minimum;
multiples of 4
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.
Network
Information
Service (NIS+)
Domain
64 1 octet minimum Name of the client NIS+ domain. The domain is formatted
as a character string consisting of characters from the NVT
ASCII character set.
Network
Information
Service (NIS+)
Servers
65 4 octet minimum;
multiples of 4
List of IP addresses indicating NIS+ servers available to
the client. Servers should be in order of preference.
Mobile IP Home
Agent
68 0 octets
minimum;
multiples of 4;
expected, 4 octets
(single home
agent address)
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
Simple Mail
Transport
Protocol
(SMTP) Server
69 4 octet minimum;
multiples of 4
List of SMTP servers available to the client. Servers
should be in order of preference.
Post Office
Protocol (POP3)
Server
70 4 octet minimum;
multiples of 4
List of POP3 servers available to the client. Servers should
be in order of preference.
Network News
Transport
Protocol
(NNTP) Server
71 4 octet minimum;
multiples of 4
List of NNTP servers available to the client. Servers should
be in order of preference.
World Wide Web
(WWW) Server
72 4 octet minimum;
multiples of 4
List of World Wide Web (WWW) servers available to the
client. Servers should be in order of preference.
Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description

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Option Descriptions
DHCPv4 Extension Options
Table B-7 lists the DHCPv4 extension options.
Finger Server 73 4 octet minimum;
multiples of 4
List of Finger servers available to the client. Servers
should be in order of preference.
Internet Relay
Chat Server
74 4 octet minimum;
multiples of 4
List of IRC servers available to the client. Servers should
be in order of preference.
StreetTalk
Server
75 4 octet minimum;
multiples of 4
List of StreetTalk servers available to the client. Servers
should be in order of preference.
StreetTalk
Directory
Assistance
(STDA) Server
76 4 octet minimum;
multiples of 4
List of STDA servers available to the client. Servers should
be in order of preference.
Table B-6 Application and Service Parameter Options (continued)
Option Name No. Length Description
Table B-7 DHCPv4 Extensions
Option Name No. Length Description
Requested IP
Address
50 4 octets Used in a client request (DHCPDISCOVER) to allow the client to
request that a particular IP address be assigned.
IP Address
Lease Time
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

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Option Descriptions
Server Identifier 54 4 octets Used in DHCPOFFER and DHCPREQUEST messages, and can
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.
Parameter
Request List
55 1 octet
minimum
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.
Message 56 1 octet
minimum
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
noctets of NVT ASCII text, which the client can display on an
available output device.
Maximum
DHCP Message
Size
57 2 octets Maximum-length DHCP message that a server is willing to accept.
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
Renewal (T1)
Time Value
58 4 octets Time interval from address assignment until the client transitions
to RENEWING state.
Value: seconds, as 32-bit unsigned integer
Rebinding (T2)
Time Value
59 4 octets Time interval from address assignment until the client transitions
to REBINDING state.
Value: seconds, as 32-bit unsigned integer
Vendor Class
Identifier
60 1 octet
minimum
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.
Table B-7 DHCPv4 Extensions (continued)
Option Name No. Length Description

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Option Descriptions
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.
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
66 1 octet
minimum
Identifies a TFTP server when the sname field in the DHCP header
has been used for DHCP options.
Bootfile Name 67 1 octet
minimum
Identifies a bootfile when the file field is the DHCP header that has
been used for DHCP options.
Relay Agent
Information
82 Identifies the DHCP relay agent information.
iSNS 83 14 bytes
minimum
Identifies the Internet Storage Name Service (see RFC 4174)
BCMS
Controller
Domain
88 Variable List of Broadcast and Multicast Service (BCMS) controller
domains (see RFC 4280)
BCMS Address 89 4 octets
minimum
List of IP addresses for the BCMS controller (see RFC 4280)
Lease Query
Client Last
Transaction
Time
91 4 octets Time of the most recent access of the client sending a
DHCPLEASEQUERY (see RFC 4388).
Lease Query
Associated IP
Addresses
92 4 octets
minimum
All IP addresses associated with the client specified in a particular
DHCPLEASEQUERY message (see RFC 4388).
Table B-7 DHCPv4 Extensions (continued)
Option Name No. Length Description

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Option Descriptions
Table B-8 DHCPv6 Options
Network Registrar Name
(Type) No. Description (Mod=modifiable)
client-identifier
AT _ B L O B
1 DUID identifying a client between a client and a server.
server-identifier
AT _ B L O B
2 DUID identifying a server between a client and a server.
ia-na
AT _ B L O B
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 O B
4 Temporary Addresses option with the associated parameters and
addresses.
iaaddr
AT _ B L O B
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 O RT
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 T 8
7 A server sends this option to a client to affect what server the client
selects (Mod).
elapsed-time
AT _ S H O RT
8 A client sends this option to a server to indicate how long the client
has been trying to complete a message exchange (Mod).
relay-message
AT _ B L O B
9 DHCP message in a Relay-forward or Relay-reply message.
auth
AT _ B L O B
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
12 The server sends this option to a client to indicate that the client can
unicast messages to the server.
status-code
AT _ B L O B
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
AT_ZEROSIZE
14 Signals use of the two-message exchange for address assignment.
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.

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Option Descriptions
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 O B
18 Relay agents use this option to identify the interface on which the
client message is received.
reconfigure-message
AT _ I N T 8
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
20 Clients use this option to announce to the server whether the client is
willing to accept Reconfigure messages.
sip-servers-name
AT _ D N S NA M E
21 Domain names of the SIP outbound proxy servers for the client (Mod).
See RFC 3319.
sip-servers-address
AT_IP6ADDR
22 IPv6 addresses of the SIP outbound proxy servers for the client (Mod).
dns-servers
AT_IP6ADDR
23 IPv6 addresses of DNS recursive name servers (Mod).
domain-list
AT _ D N S NA M E
24 Domain names in the domain search list (Mod).
ia-pd
AT _ B L O B
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 O B
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
27 List of IPv6 addresses of Network Information Service (NIS) servers
available to the client (see RFC 3898) (Mod).
nisp-servers
AT_IP6ADDR
28 List of IPv6 addresses of NIS+ servers available to the client (Mod).
nis-domain-name
AT _ D N S NA M E
29 Conveys the NIS domain name to the client (Mod).
nisp-domain-name
AT _ D N S NA M E
30 Conveys the NIS+ domain name to the client (Mod).
sntp-servers
AT_IP6ADDR
31 List of Simple Network Time Protocol (SNTP) servers available to the
client (see RFC 4075) (Mod).
info-refresh-time
AT _ T I M E
32 Sets an upper bound for how long a client should wait before
refreshing DHCPv6 information (see RFC 4242) (Mod).
bcms-server-d
AT _ D N S NA M E
33 List of BCMS controller domains (see RFC 4280) (Mod).
bcms-server-a
AT_IP6ADDR
34 List of IPv6 addresses for the Broadcast and Multicast Service
(BCMS) controller (see RFC 4280) (Mod).
Table B-8 DHCPv6 Options (continued)
Network Registrar Name
(Type) No. Description (Mod=modifiable)

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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Descriptions
Microsoft Client Options
Table B-9 lists the standard Microsoft client options.
geoconf-civic
AT _ B L O B
36 DHCP civic addresses configuration (Mod).
remote-id
AT _ B L O B
37 Relay agents that terminate switched or permanent circuits can add
this option to identify remote hosts (see RFC 4649) (Mod).
relay-agent-subscriber-id
AT _ B L O B
38 Allows assignment and activation of subscriber-specific actions (see
RFC 4580) (Mod).
client-fqdn
AT _ B L O B
39 DHCP client FQDN (Mod).
new-posix-timezone
AT _ B L O B
41 POSIX time zone, for example, EST5EDT4,
M3.2.0/02:00,M11.1.0/02:00.
new-tzdb-timezone
AT _ B L O B
42 POSIX time zone database name, for example, Europe/Zurich.
ero
AT _ B L O B
43 Relay agent Echo Request option to inform the server of the list of
relay agent options to echo back.
lq-query
AT _ B L O B
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 O B
45 Encapsulates the data for a single client on a single link in a
LEASEQUERY-REPLY message.
clt-time
AT _ T I M E
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 O B
47 Used only in a LEASEQUERY-REPLY message; provides the relay
agent data used when the client last communicated with the server.
lq-client-link
AT_IP6ADDR
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 S NA M E
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.
Table B-8 DHCPv6 Options (continued)
Network Registrar Name
(Type) No. Description (Mod=modifiable)
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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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Tables
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.
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.
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
a warning if it is not present
routers 3 IP address of the router for this subnet
Table B-9 Microsoft DHCP Client Options (continued)
Option Name No. Description
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 _ I PA D D R
2 time-offset Time Offset AT _ S T I M E Replaced by tz-
options
(RFC 4833)
3 routers Router AT _ I PA D D R 1+
4 time-servers Time Server AT _ I PA D D R 1+
5 name-servers Name Server AT _ I PA D D R 1+
6 domain-name-servers Domain Server AT _ I PA D D R 1+
7 log-servers Log Server AT _ I PA D D R 1+
8 cookie-servers Quotes Server AT _ I PA D D R 1+

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Option Tables
9 lpr-servers LPR Server AT_ I PA D D R 1+
10 impress-servers Impress Server AT _ I PA D D R 1+
11 resource-location-servers RLP Server AT _ I PA D D R 1+
12 host-name Host Name AT _ N S T R I N G
13 boot-size Boot File Size AT _ S HO RT
14 merit-dump Merit Dump File AT _ N S T R I N G
15 domain-name Domain Name AT _ N S T R I N G
16 swap-server Swap Server AT _ I PA D D R
17 root-path Root Path AT _ N S T R I N G
18 extensions-path Extension File AT _ N S T R I 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 D D R 2n
22 max-dgram-reassembly Maximum DG
Assembly
AT _ S H O RT
23 Default-ip-ttl Default IP TTL AT_RANGEBYTE
24 path-mtu-aging-timeout MTU Timeout AT _ T I M E
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 _ I PA D D 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 D D R
33 static-routes Static Route AT _ I PA D D R 2n
34 trailer-encapsulation Trailers AT_BOOL
35 arp-cache-timeout ARP Timeout AT _ T I M E
36 ieee802.3-encapsulation Ethernet AT_BOOL
37 default-tcp-ttl Default TCP TTL AT_RANGEBYTE
38 tcp-keepalive-interval Keepalive Time AT _ T I M E
39 tcp-keepalive-garbage Keepalive Data AT_BOOL
40 nis-domain NIS Domain AT _ S T R I N G
41 nis-servers NIS Servers AT _ I PA D D R 1+
42 ntp-servers NTP Servers AT_ I PA D D R 1+
43 vendor-encapsulated-
options
Vendor Specific AT _ B L O B NM
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments

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Option Tables
44 netbios-name-servers NetBIOS Name Server AT _ I PA D D R 1+
45 netbios-dd-servers NetBIOS Distribution
Server
AT _ I PA D D R 1+
46 netbios-node-type NetBIOS Node Type AT_RANGEBYTE
47 netbios-scope NetBIOS Scope AT _ N S T R I N G
48 font-servers X Window Font AT _ I PA D D R 1+
49 x-display-managers X Window Manager AT _ IPA D D R 1+
50 dhcp-requested-address Address Request AT _ I PA D D R
51 dhcp-lease-time Address Time AT _ T I M E NM
52 dhcp-option-overload Overload AT _ OV E R L 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 D D R
55 dhcp-parameter-request-
list
Parameter List AT _ I N T 8 0+
56 dhcp-message DHCP Message AT _ N S T R I N G NM
57 dhcp-max-message-size DHCP Maximum
Message Size
AT _ S H O RT NM
58 dhcp-renewal-time Renewing Time AT _ T I M E NM
59 dhcp-rebinding-time Rebinding Time AT _ TI M E NM
60 dhcp-class-identifier Class Identifier AT _ N S T R IN G
61 dhcp-client-identifier Client Identifier AT _ B L O B
62 netwareip-domain NetWare/IP Domain AT _ N S T R I N G
63 netwareip-information NetWare/IP Option AT _ B L O B
64 nis+-domain NIS Domain Name AT _ N S T R I N G
65 nis+-servers NIS Server Address AT _ I PA D D R 1+
66 tftp-server TFTP Server Name AT _ N S T R I N G
67 boot-file Bootfile Name AT _ N S T R IN G
68 mobile-ip-home-agents Mobile IP Home Agent AT _ I PA D D R 0+
69 smtp-servers SMTP Server AT _ I PA D D R 1+
70 pop3-servers POP3 Server AT _ I PA D D R 1+
71 nntp-servers NNTP Server AT _ I PA D D R 1+
72 www-servers WWW Server AT _ I PA D D R 1+
73 finger-servers Finger Server AT _ I PA D D R 1+
74 irc-servers IRC Server AT _ I PA D D R 1+
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments

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Option Tables
75 streettalk-servers StreetTalk Server AT _ I PA D D R 1+
76 streettalk-directory-
assistance-servers
STDA Server AT _ I PA D D R 1+
77 dhcp-user-class-id User Class ID AT_TYPECNT Suboptions (2)
78 slp-directory-agent Service Location
Protocol Directory
Agent
AT _ B L O B Suboptions (2)
79 slp-service-scope SLP Service Scope AT _ B L O B Suboptions (2)
80 rapid-commit Rapid Commit AT_ZEROSIZE
81 client-fqdn Client FQDN AT _ B L O B Suboptions (4)
82 relay-agent-info Relay Agent
Information
AT _ B L O B For suboptions,
see Table C-3 on
page C-2
83 iSNS Internet Storage Name
Service (RFC4174)
AT _ B L O B Suboptions (7)
85 nds-servers NDS Servers AT _ I PA D D R 1+
86 nds-tree NDS Tree Name AT _ N S T R I N G
87 nds-context NDS Context AT _ N S T R I N G
88 bcms-servers-d BCMS Controller
Domain (RFC 4280)
AT _ D N S NA M E 1+
89 bcms-servers-a BCMS Address AT _ I PA D D R 1+
90 authentication Authentication AT _ B L O B Suboptions (5)
91 client-last-transaction-
time
Lease Query Client
Last Transaction Time
AT _ T I M E
92 associated-ip Lease Query
Associated IP
Addresses
AT _ I PA D D R 1+
93 pxe-client-arch AT _ S H O RT
94 pxe-client-network-id AT _ B L O B Suboptions (2)
95 ldap-url AT _ N S T R I N G
97 pxe-client-machine-id AT _ B L O B Suboptions (2)
98 user-auth AT _ N S T R I N G
99 geoconf-civic Civic Addresses
Configuration
AT _ B L O B
100 tz-posix IEEE 1003.1 String AT _ N S T R I N G
101 tz-database Time Zone Database AT _ N S T R I N G
112 netinfo-parent-server-addr AT _ I PA D D R
113 netinfo-parent-server-tag AT _ N S T R I N G
114 initial-url AT _ N S T R I N G
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments

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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Tables
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.)
116 auto-configure Autoconfiguration AT_RANGEBYTE
117 name-service-search Name Service Search AT_ S H O RT 1+
118 subnet-selection Subnet Selection AT _ I PA D D R
119 domain-search Domain Search AT _ B L O B
120 sip-servers SIP Servers AT _ B L O B Suboptions (2)
121 classless-static-route Classless Static Route AT _ B L O B
122 cablelabs-client-
configuration)
CableLabs Client
Configuration
AT _ B L O B Suboptions (10)
(see
cablelabs-client-
configuration,
page C-3)
123 geo-conf GeoConf Option AT _ B L O B
124 v-i-vendor-class Vendor-Identifying
Vendor Class
AT_VENDOR_CLASS NM
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 D D R
161 cisco-leased-ip Cisco AT _ I PA D D R
162 cisco-client-requested-
host-name
Cisco AT _ N S T R IN G
163 cisco-client-last-
transaction-time
Cisco AT _ I N T
185 vpn-id VPN Identifier AT _ B L O B NM: Suboptions
(2)
220 subnet-alloc Subnet Allocation AT _ B L O B Suboptions (5)
221 cisco-vpn-id Cisco VPN Identifier AT _ B L O B Suboptions (2)
251 cisco-auto-configure Cisco
Autoconfiguration
AT_RANGEBYTE
255 end End AT_NOLEN NM
Table B-10 DHCPv4 Options by Number (continued)
No. Network Registrar Name Protocol Name Validation Comments

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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
Time
DHCPv4
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 1Client Identifier DHCPv6
client-last-transaction-time 91 Leasequery Client Last
Transaction Time
DHCPv4
clt-time 46 Leasequery Client Last
Transaction Time
DHCPv6
cookie-servers 8Cookie 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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Part 6: Appendices, Glossary, and Index Appendix B DHCP Options
Option Tables
dhcp-max-message-size 57 Maximum DHCP
Message Size
DHCPv4
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
Lease Information,
MS DHCP Client
dhcp-renewal-time 58 Renewing (T1)
Time Value
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 6Domain Name Server Basic, MS DHCP Client
domain-search 119 Domain Search DHCPv4
elapsed-time 8Elapsed 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
Font Server
Servers
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 3Identity Association for
Nontemporary Addresses
DHCPv6
ia-pd 25 Prefix Delegation DHCPv6
ia-ta 4Identity Association for
Temporary Addresses
DHCPv6
iaaddr 5IA Address DHCPv6
iaprefix 26 IA Prefix DHCPv6
ieee802.3-encapsulation 36 Ethernet Encapsulation Interface
impress-servers 10 Impress Server BOOTP
Table B-11 DHCP Options by Network Registrar Name (continued)
Network Registrar Name No. Option Name Category