| Option number | Option | Description
|
| 1 | Subnet mask | The subnet mask option specifies the client's subnet mask
as per Request for Comments (RFC) 950. If both the subnet mask and the
router option are specified in a DHCP reply, the subnet mask option must be
specified first. The code for the subnet mask option is 1, and its length is
4 octets.
subnet mask option
|
| 2 | Time offset | The time offset field specifies the offset of the client's
subnet in seconds from Coordinated Universal Time (UTC). The offset is
expressed as a two's 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.
The code for the time offset option is 2, and its length is 4 octets.
time offset option
|
| 3 | Router | The router option specifies a list of IP addresses for routers
on the client's subnet. Routers should be listed in order of preference.
The code for the router option is 3. The minimum length for the router
option is 4 octets, and the length must always be a multiple of 4.
router option
|
| 4 | Time server | The time server option specifies a list of RFC 868 time
servers available to the client. Servers should be listed in order of
preference.
The code for the time server option is 4. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
time server option
|
| 5 | Name server | The name server option specifies a list of IEN 116 name
servers available to the client. Servers should be listed in order of
preference.
The code for the name server option is 5. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
name server option
|
| 6 | Domain Name Server | The domain name server option specifies a list of
Domain Name System (STD 13, RFC 1035) name servers available to the client.
Servers should be listed in order of preference.
The code for the domain name server option is 6. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
domain name server option
|
| 7 | Log server | The log server option specifies a list of MIT-LCS UDP log
servers available to the client. Servers should be listed in order of
preference.
The code for the log server option is 7. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
log server option
|
| 8 | Cookie server | The cookie server option specifies a list of RFC 865
cookie servers available to the client. Servers should be listed in order of
preference.
The code for the cookie server option is 8. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
cookie server option
|
| 9 | LPR server | The LPR server option specifies a list of RFC 1179 line
printer servers available to the client. Servers should be listed in order
of preference.
The code for the LPR server option is 9. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
LPR server option
|
| 10 | Impress server | The Impress server option specifies a list of Imagen
Impress servers available to the client. Servers should be listed in order
of preference.
The code for the Impress server option is 10. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
impress server option
|
| 11 | Resource location server | This option specifies a list of RFC 887
Resource Location servers available to the client. Servers should be listed
in order of preference.
The code for this option is 11. The minimum length for this option is 4
octets, and the length must always be a multiple of 4.
resource location server option
|
| 12 | Host name | This option specifies the name of the client. The name
might or might not be qualified with the local domain name (see section 3.17
for the preferred way to retrieve the domain name). See RFC 1035 for
character set restrictions.
The code for this option is 12, and its minimum length is 1.
host name option
|
| 13 | Boot file size | This option specifies the length in 512-octet blocks
of the default boot image for the client. The file length is specified as an
unsigned 16-bit integer.
The code for this option is 13, and its length is 2.
boot file size option
|
| 14 | Merit dump file | This option specifies the path-name of a file to
which the client's core image should be dumped in the event the client
crashes. The path is formatted as a character string consisting of
characters from the NVT ASCII character set.
The code for this option is 14. Its minimum length is 1.
merit dump file option
|
| 15 | Domain name | This option specifies the domain name that client should
use when resolving hostnames through the Domain Name System.
The code for this option is 15. Its minimum length is 1.
domain name option
|
| 16 | Swap server | This specifies the IP address of the client's swap
server.
The code for this option is 16, and its length is 4.
swap server option
|
| 17 | Root path | This option specifies the path-name that contains the
client's root disk. The path is formatted as a character string consisting
of characters from the NVT ASCII character set.
The code for this option is 17. Its minimum length is 1.
root path option
|
| 18 | Extensions path | A string to specify a file, retrievable via TFTP,
which contains information that can be interpreted in the same way as the 64
-octet vendor-extension field within the BOOTP response, with the following
exceptions:
The length of the file is unconstrained
All references to Tag 18 (that is, instances of the BOOTP Extensions
Path field) within the file are ignored.
The code for this option is 18. Its minimum length is 1.
extensions path option
|
| 19 | IP forwarding | This option specifies whether the client should
configure its IP layer for packet forwarding. A value of 0 means disable IP
forwarding, and a value of 1 means enable IP forwarding.
The code for this option is 19, and its length is 1.
IP forwarding option
|
| 20 | Non-Local source routing | This option specifies whether the client
should configure its IP layer to allow forwarding of datagrams with non
-local source routes. A value of 0 means disallow forwarding of such
datagrams, and a value of 1 means allow forwarding.
The code for this option is 20, and its length is 1.
non-local source routing option
|
| 21 | Policy filter | This option specifies policy filters for non-local
source routing. The filters consist of a list of IP addresses and masks
which 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.
The code for this option is 21. The minimum length of this option is 8, and
the length must be a multiple of 8.
policy filter option
|
| 22 | Maximum datagram reassembly size | This option specifies the maximum
size datagram that the client should be prepared to reassemble. The size is
specified as a 16-bit unsigned integer. The minimum value legal value is
576.
The code for this option is 22, and its length is 2.
maximum datagram reassembly size option
|
| 23 | Default IP time to live | This option specifies the default time-to
-live that the client should use on outgoing datagrams. The TTL is specified
as an octet with a value between 1 and 255.
The code for this option is 23, and its length is 1.
default IP time to live option
|
| 24 | Path MTU aging timeout | This option specifies the timeout (in seconds)
to use when aging Path MTU values discovered by the mechanism defined in RFC
1191. The timeout is specified as a 32-bit unsigned integer.
The code for this option is 24, and its length is 4.
path MTU aging timeout option
|
| 25 | Path MTU plateau table | This option specifies a 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. The minimum MTU value cannot be smaller than 68.
The code for this option is 25. Its minimum length is 2, and the length must
be a multiple of 2.
path MTU plateau table option
|
| 26 | Interface MTU | This option specifies the MTU to use on this interface.
The MTU is specified as a 16-bit unsigned integer. The minimum legal value
for the MTU is 68.
The code for this option is 26, and its length is 2.
interface MTU option
|
| 27 | All subnets are local | This option specifies whether 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. A value of 1 indicates that all subnets share the same
MTU. A value of 0 means that the client should assume that some subnets of
the directly connected network might have smaller MTUs.
The code for this option is 27, and its length is 1.
all subnets are local option
|
| 28 | Broadcast address | This option specifies the broadcast address in use
on the client's subnet. Legal values for broadcast addresses are specified
in section 3.2.1.3 of RFC 2132.
The code for this option is 28, and its length is 4.
broadcast address option
|
| 29 | Perform mask discovery | This option specifies whether the client
should perform subnet mask discovery using ICMP. A value of 0 indicates that
the client should not perform mask discovery. A value of 1 means that the
client should perform mask discovery.
The code for this option is 29, and its length is 1.
perform mask discovery option
|
| 30 | Mask supplier | This option specifies whether the client should respond
to subnet mask requests using ICMP. A value of 0 indicates that the client
should not respond. A value of 1 means that the client should respond.
The code for this option is 30, and its length is 1.
mask supplier option
|
| 31 | Perform router discovery | This option specifies whether the client
should solicit routers using the Router Discovery mechanism defined in RFC
1256. A value of 0 indicates that the client should not perform router
discovery. A value of 1 means that the client should perform router
discovery.
The code for this option is 31, and its length is 1.
perform router discovery option
|
| 32 | Router solicitation address option | This option specifies the address
to which the client should transmit router solicitation requests.
The code for this option is 32, and its length is 4.
router solicitation address option
|
| 33 | Static route | This option specifies a list of static routes that the
client should install in its routing cache. If multiple routes to the same
destination are specified, they are listed 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.
The code for this option is 33. The minimum length of this option is 8, and
the length must be a multiple of 8.
static route option
|
| 34 | Trailer encapsulation | This option specifies whether the client should
negotiate the use of trailers (RFC 893) when using the ARP protocol. A value
of 0 indicates that the client should not attempt to use trailers. A value
of 1 means that the client should attempt to use trailers.
The code for this option is 34, and its length is 1.
trailer encapsulation option
|
| 35 | ARP cache timeout | This option specifies the timeout in seconds for
ARP cache entries. The time is specified as a 32-bit unsigned integer.
The code for this option is 35, and its length is 4.
ARP cache timeout option
|
| 36 | Ethernet encapsulation | This option specifies whether the client
should use Ethernet Version 2 (RFC 894) or IEEE 802.3 (RFC 1042)
encapsulation if the interface is an Ethernet. A value of 0 indicates that
the client should use RFC 894 encapsulation. A value of 1 means that the
client should use RFC 1042 encapsulation.
The code for this option is 36, and its length is 1.
ethernet encapsulation option
|
| 37 | TCP default TTL | This option specifies the default TTL that the client
should use when sending TCP segments. The value is represented as an 8-bit
unsigned integer. The minimum value is 1.
The code for this option is 37, and its length is 1.
TCP default TTL option
|
| 38 | TCP keep-alive interval | This option specifies the 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.
The code for this option is 38, and its length is 4.
TCP keep-alive interval option
|
| 39 | TCP keep-alive garbage | This option specifies whether the client
should send TCP keepalive messages with an octet of garbage for
compatibility with older implementations. A value of 0 indicates that a
garbage octet should not be sent. A value of 1 indicates that a garbage
octet should be sent.
The code for this option is 39, and its length is 1.
TCP keep-alive garbage option
|
| 40 | Network information service domain | This option specifies the name of
the client's NIS domain. The domain is formatted as a character string
consisting of characters from the NVT ASCII character set.
The code for this option is 40. Its minimum length is 1.
network information service domain option
|
| 41 | Network information servers | This option specifies a list of IP
addresses indicating NIS servers available to the client. Servers should be
listed in order of preference.
The code for this option is 41. Its minimum length is 4, and the length must
be a multiple of 4.
network information servers option
|
| 42 | Network time protocol servers option | This option specifies a list of
IP addresses indicating NTP servers available to the client. Servers should
be listed in order of preference.
The code for this option is 42. Its minimum length is 4, and the length must
be a multiple of 4.
network time protocol servers option
|
| 44 | NetBIOS over TCP/IP name server | The NetBIOS name server (NBNS) option
specifies a list of RFC 1001/1002 NBNS name servers listed in order of
preference.
The code for this option is 44. The minimum length of the option is 4
octets, and the length must always be a multiple of 4.
NetBIOS over TCP/IP name server option
|
| 45 | NetBIOS over TCP/IP datagram distribution server | The NetBIOS datagram
distribution server (NBDD) option specifies a list of RFC 1001/1002 NBDD
servers listed in order of preference.
The code for this option is 45. The minimum length of the option is 4
octets, and the length must always be a multiple of 4.
NetBIOS over TCP/IP datagram distribution server option
|
| 46 | NetBIOS over TCP/IP node type | The NetBIOS node type option allows
NetBIOS over TCP/IP clients which are configurable to be configured as
described in RFC 1001/1002. The value is specified as a single octet which
identifies the client type as follows:
node type value
In the above chart, the notation '0x' indicates a number in base-16
(hexadecimal).
The code for this option is 46. The length of this option is always 1.
NetBIOS over TCP/IP node type option
|
| 47 | NetBIOS over TCP/IP scope | The NetBIOS scope option specifies the
NetBIOS over TCP/IP scope parameter for the client as specified in RFC
1001/1002.
The code for this option is 47. The minimum length of this option is 1.
NetBIOD over TCP/IP scope option
|
| 48 | X Window System Font server | This option specifies a list of X Window
System Font servers available to the client. Servers should be listed in
order of preference.
The code for this option is 48. The minimum length of this option is 4
octets, and the length must be a multiple of 4.
X Window System Font server option
|
| 49 | X Window System display manager | This option specifies a list of IP
addresses of systems that are running the X Window System Display Manager
and are available to the client.
Addresses should be listed in order of preference.
The code for the this option is 49. The minimum length of this option is 4,
and the length must be a multiple of 4.
X Window System display manager option
|
| 51 | IP address lease time | This option is 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.
The time is in units of seconds, and is specified as a 32-bit unsigned
integer.
The code for this option is 51, and its length is 4.
IP address lease time option
|
| 58 | Renewal (T1) time value | This option specifies the time interval from
address assignment until the client transitions to the RENEWING state.
The value is in units of seconds, and is specified as a 32-bit unsigned
integer.
The code for this option is 58, and its length is 4.
renewal(T1) time value option
|
| 59 | Rebinding (T2) time value | This option specifies the time interval
from address assignment until the client transitions to the REBINDING
state.
The value is in units of seconds, and is specified as a 32-bit unsigned
integer.
The code for this option is 59, and its length is 4.
rebinding(T2) time value option
|
| 62 | NetWare/IP domain name | Specifies the Netware/IP domain name.
|
| 63 | NetWare/IP | Specifies the NetWare sub-options you want. The range is 1
to 255. Use option 62 to specify the NetWare/IP domain name.
|
| 64 | NIS domain name | This option specifies the name of the client's NIS+
domain. The domain is formatted as a character string consisting of
characters from the NVT ASCII character set.
The code for this option is 64. Its minimum length is 1.
NIS domain name option
|
| 65 | NIS servers |
This option specifies a list of IP addresses indicating NIS+ servers
available to the client. Servers should be listed in order of preference.
The code for this option is 65. Its minimum length is 4, and the length must
be a multiple of 4.
NIS servers option
|
| 66 | Server name | This option is used to identify a TFTP server when the
'sname' field in the DHCP header has been used for DHCP options.
The code for this option is 66, and its minimum length is 1.
Server name option
|
| 67 | Boot file name | This option is used to identify a bootfile when the
'file' field in the DHCP header has been used for DHCP options.
The code for this option is 67, and its minimum length is 1.
Boot file name option
|
| 68 | Home address | This option specifies a list of IP addresses indicating
mobile IP home agents available to the client. Agents should be listed in
order of preference.
The code for this option is 68. Its minimum length is 0 (indicating no home
agents are available) and the length must be a multiple of 4. It is expected
that the usual length will be four octets, containing a single home agent's
address.
Home address option
|
| 69 | SMTP servers | The SMTP server option specifies a list of SMTP servers
available to the client. Servers should be listed in order of preference.
The code for the SMTP server option is 69. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
SMTP servers option
|
| 70 | POP3 server |
The POP3 server option specifies a list of POP3 available to the client.
Servers should be listed in order of preference.
The code for the POP3 server option is 70. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
POP3 server option
|
| 71 | NNTP server | The NNTP server option specifies a list of NNTP available
to the client. Servers should be listed in order of preference.
The code for the NNTP server option is 71. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
NNTP server option
|
| 72 | WWW server | The WWW server option specifies a list of WWW available to
the client. Servers should be listed in order of preference.
The code for the WWW server option is 72. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
WWW server option
|
| 73 | Finger server | The Finger server option specifies a list of Finger
available to the client. Servers should be listed in order of preference.
The code for the Finger server option is 73. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
Finger server option
|
| 74 | IRC server | The IRC server option specifies a list of IRC available to
the client. Servers should be listed in order of preference.
The code for the IRC server option is 74. The minimum length for this option
is 4 octets, and the length must always be a multiple of 4.
IRC server option
|
| 75 | StreetTalk server | The StreetTalk server option specifies a list of
StreetTalk servers available to the client. Servers should be listed in
order of preference.
The code for the StreetTalk server option is 75. The minimum length for this
option is 4 octets, and the length must always be a multiple of 4.
StreetTalk server option
|
| 76 | STDA server | The StreetTalk Directory Assistance (STDA) server option
specifies a list of STDA servers available to the client. Servers should be
listed in order of preference.
The code for the StreetTalk Directory Assistance server option is 76. The
minimum length for this option is 4 octets, and the length must always be a
multiple of 4.
STDA server option
|
| 77 | User class | Specifies the class name of which the host is a member.
You must have previously defined this class to the DHCP server during DHCP
server configuration.
|
| 78 | Directory agent | Specifies the IP address of the directory agent if
clients use Service Location Protocol to transact messages.
|
| 79 | Service scope | Specifies the scope of the directory agent that uses
Service Location Protocol to respond to service request messages.
|
| 80 | Naming authority | Specifies the naming authority for the directory
agent if clients use Service Location Protocol to transact messages. The
naming authority specifies the syntax for schemes that are used in URLs.
Parent topic:
DHCP concepts
|