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Updated: Thursday, June 13, 2019
 
 

dhcp_inittab(5)

Name

dhcp_inittab - information repository for DHCP options

Description

The /etc/dhcp/inittab and the /etc/dhcp/inittab6 files contain information about the Dynamic Host Configuration Protocol (DHCP) options, which are network configuration parameters passed from DHCP servers to DHCP clients when a client machine uses DHCP. Since many DHCP-related commands must parse and understand these DHCP options, this file serves as a central location where information about these options may be obtained.

The DHCP inittab and inittab6 files provide three general pieces of information:

  • A mnemonic alias, or symbol name, for each option number. For instance, option 12 is aliased to the name Hostname. This is useful for DHCP-related programs that require human interaction, such as dhcpinfo(1).

  • Information about the syntax for each option. This includes information such as the type of the value, for example, whether it is a 16-bit integer or an IP address.

  • The policy for what options are visible to which DHCP-related programs.

If you make any changes to the /etc/dhcp/inittab file, note that only additions of or changes to SITE options are preserved during upgrade. For /etc/dhcp/inittab6, no options are preserved during upgrade.

The VENDOR options defined here are intended for use by the Solaris DHCP client and DHCP management tools. The SUNW vendor space is owned by Sun, and changes are likely during upgrade. If you need to configure the Solaris DHCP server to support the vendor options of a different client, see dhcptab for details.

Each DHCP option belongs to a certain category, which roughly defines the scope of the option; for instance, an option may only be understood by certain hosts within a given site, or it may be globally understood by all DHCP clients and servers. The following categories are defined; the category names are not case-sensitive:

STANDARD

All client and server DHCP implementations agree on the semantics. These are administered by the Internet Assigned Numbers Authority (IANA). These options are numbered from 1 to 127 for IPv4 DHCP, and 1 to 65535 for DHCPv6.

SITE

Within a specific site, all client and server implementations agree on the semantics. However, at another site the type and meaning of the option may be quite different. These options are numbered from 128 to 254 for IPv4 DHCP. DHCPv6 does not support site options.

VENDOR

Each vendor may define 254 options (65536 for DHCPv6) unique to that vendor. The vendor is identified within a DHCP packet by the “Vendor Class” option, number 60 (number 17 for DHCPv6). An option with a specific numeric identifier belonging to one vendor will, in general, have a type and semantics different from that of a different vendor. Vendor options are “super-encapsulated” into the vendor field number 43, as defined in RFC 2132 for IPv4 DHCP, and number 17 as defined in RFC 3315 for DHCPv6. The /etc/dhcp/inittab file contains only Sun vendor options. Define non-Sun vendor options in the dhcptab file.

FIELD

This category allows the fixed fields within a DHCP packet to be aliased to a mnemonic name for use with dhcpinfo(1).

INTERNAL

This category is internal to the Solaris DHCP implementation and will not be further defined.

DHCP inittab and inittab6 Format

Data entries are written one per line and have seven fields; each entry provides information for one option. Each field is separated by a comma, except for the first and second, which are separated by whitespace (as defined in isspace(3C)). An entry cannot be continued onto another line. Blank lines and those whose first non-whitespace character is '#' are ignored.

The fields, in order, are:

  • Mnemonic Identifier

    The Mnemonic Identifier is a user-friendly alias for the option number; it is not case sensitive. This field must be per-category unique and should be unique across all categories. The option names in the STANDARD, SITE, and VENDOR spaces should not overlap, or the behavior will be undefined. See Mnemonic Identifiers for Options section of this man page for descriptions of the option names.

  • Category (scope)

    The Category field is one of STANDARD, SITE, VENDOR, FIELD, or INTERNAL and identifies the scope in which the option falls. SITE is not used in inittab6.

  • Option Number

    The Option Number is the number of this option when it is in a DHCP packet. This field should be per-category unique and the STANDARD and SITE fields should not have overlapping code fields or the behavior is undefined.

  • Data Type

    Data Type is one of the following values, which are not case sensitive:

    ASCII

    A printable character string

    Bool

    Has no value. Scope limited to category limited to INTERNAL. Presence of an option of this type within a Solaris configuration file represents TRUE, absence represents FALSE.

    Octet

    An array of bytes

    Unumber8

    An 8-bit unsigned integer

    Snumber8

    An 8-bit signed integer

    Unumber16

    A 16-bit unsigned integer

    Snumber16

    A 16-bit signed integer

    Unumber24

    A 24-bit unsigned integer

    Unumber32

    A 32-bit unsigned integer

    Snumber32

    A 32-bit signed integer

    Unumber64

    A 64-bit unsigned integer

    Snumber64

    A 64-bit signed integer

    Ip

    An IPv4 address

    Ipv6

    An IPv6 address

    Duid

    An RFC 3315 Unique Identifier

    Domain

    An RFC 1035-encoded domain name

    The data type field describes an indivisible unit of the option payload, using one of the values listed above.

  • Granularity

    The Granularity field describes how many indivisible units in the option payload make up a whole value or item for this option. The value must be greater than zero (0) for any data type other than Bool, in which case it must be zero ( 0).

  • Maximum Number Of Items

    This value specifies the maximum items of Granularity which are permissible in a definition using this symbol. For example, there can only be one IP address specified for a subnet mask, so the Maximum number of items in this case is one (1). A Maximum value of zero (0) means that a variable number of items is permitted.

  • Visibility

    The Visibility field specifies which DHCP-related programs make use of this information, and should always be defined as sdmi for newly added options.

Mnemonic Identifiers for IPv4 Options

The following table maps the mnemonic identifiers used in Solaris DHCP to RFC 2132 and RFC 3442 options:

Symbol
Code
Description
Subnet
1
Subnet Mask, dotted Internet address (IP).
UTCoffst
2
Coordinated Universal time offset (seconds).
Router
3†
List of Routers, IP.
Timeserv
4
List of RFC-868 servers, IP.
IEN116ns
5
List of IEN 116 name servers, IP.
DNSserv
6
List of DNS name servers, IP.
Logserv
7
List of MIT-LCS UDP log servers, IP.
Cookie
8
List of RFC-865 cookie servers, IP.
Lprserv
9
List of RFC-1179 line printer servers, IP.
Impress
10
List of Imagen Impress servers, IP.
Resource
11
List of RFC-887 resource location servers, IP.
Hostname
12
Client's hostname, value from hosts database.
Bootsize
13
Number of 512 octet blocks in boot image, NUMBER.
Dumpfile
14
Path where core image should be dumped, ASCII.
DNSdmain
15
DNS domain name, ASCII.
Swapserv
16
Client's swap server, IP.
Rootpath
17
Client's Root path, ASCII.
ExtendP
18
Extensions path, ASCII.
IpFwdF
19
IP Forwarding Enable/Disable, NUMBER.
NLrouteF
20
Non-local Source Routing, NUMBER.
PFilter
21
Policy Filter, IP.
MaxIpSiz
22
Maximum datagram Reassembly Size, NUMBER.
IpTTL
23
Default IP Time to Live, (1=<x<=255), NUMBER.
PathTO
24
RFC-1191 Path MTU Aging Timeout, NUMBER.
PathTbl
25
RFC-1191 Path MTU Plateau Table, NUMBER.
MTU
26
Interface MTU, x>=68, NUMBER.
SameMtuF
27
All Subnets are Local, NUMBER.
Broadcst
28
Broadcast Address, IP.
MaskDscF
29
Perform Mask Discovery, NUMBER.
MaskSupF
30
Mask Supplier, NUMBER.
RDiscvyF
31
Perform Router Discovery, NUMBER.
RSolictS
32
Router Solicitation Address, IP.
StaticRt
33
Static Route, Double IP (network router).
TrailerF
34
Trailer Encapsulation, NUMBER.
ArpTimeO
35
ARP Cache Time out, NUMBER.
EthEncap
36
Ethernet Encapsulation, NUMBER.
TcpTTL
37
TCP Default Time to Live, NUMBER.
TcpKaInt
38
TCP Keepalive Interval, NUMBER.
TcpKaGbF
39
TCP Keepalive Garbage, NUMBER.
NISdmain
40
NIS Domain name, ASCII.
NISservs
41
List of NIS servers, IP.
NTPservs
42
List of NTP servers, IP.
NetBNms
44
List of NetBIOS Name servers, IP.
NetBDsts
45
List of NetBIOS Distribution servers, IP.
NetBNdT
46
NetBIOS Node type (1=B-node, 2=P, 4=M, 8=H).
NetBScop
47
NetBIOS scope, ASCII.
XFontSrv
48
List of X Window Font servers, IP.
XDispMgr
49
List of X Window Display managers, IP.
LeaseTim
51
Lease Time Policy, (-1 = PERM), NUMBER.
Message
56
Message to be displayed on client, ASCII.
T1Time
58
Renewal (T1) time, NUMBER.
T2Time
59
Rebinding (T2) time, NUMBER.
NW_dmain
62
NetWare/IP Domain Name, ASCII.
NWIPOpts
63
NetWare/IP Options, OCTET (unknown type).
TFTPsrvN
66
TFTP server hostname, ASCII.
OptBootF
67
Optional Bootfile path, ASCII.
MblIPAgt
68
Mobile IP Home Agent, IP.
SMTPserv
69
Simple Mail Transport Protocol Server, IP.
POP3serv
70
Post Office Protocol (POP3) Server, IP.
NNTPserv
71
Network News Transport Proto. (NNTP) Server, IP.
WWWservs
72
Default WorldWideWeb Server, IP.
Fingersv
73
Default Finger Server, IP.
IRCservs
74
Internet Relay Chat Server, IP.
STservs
75
StreetTalk Server, IP.
STDAservs
76
StreetTalk Directory Assist. Server, IP.
UserClas
77
User class information, ASCII.
SLP_DA
78
Directory agent, OCTET.
SLP_SS
79
Service scope, OCTET.
AgentOpt
82
Agent circuit ID, OCTET.
FQDN
89
Fully Qualified Domain Name, OCTET.
PXEarch
93
Client system architecture, NUMBER.
ClasslessRt
121†
List of Classless Static Routes, CLROUTE.
BootFile
N/A
File to Boot, ASCII.
BootPath
N/A
Boot path prefix to apply to client's requested boot file, ASCII.
BootSrvA
N/A
Boot Server, IP.
BootSrvN
N/A
Boot Server Hostname, ASCII.
EchoVC
N/A
Echo Vendor Class Identifier Flag, (Present=TRUE)
LeaseNeg
N/A
Lease is Negotiable Flag, (Present=TRUE)

Note -  defines that as per RFC 3442, if the DHCP server returns both, a Classless Static Route option and a Router option, the Solaris DHCP client ignores the Router option.

Mnemonic Identifiers for IPv6 Options

The following table maps the mnemonic identifiers used in Solaris DHCP to RFC 3315, 3319, 3646, 3898, 4075, and 4280 options:

Symbol
Code
Description
ClientID
1
Unique identifier for client, DUID
ServerID
2
Unique identifier for server, DUID
Preference
7
Server preference, NUMBER
Unicast
12
Unicast server address, IPV6
UserClass
15
User classes for client, OCTET
VendorClass
16
Vendor client hardware items, OCTET
SIPNames
21
SIP proxy server name list, DOMAIN
SIPAddresses
22
SIP proxy server addresses in preference order, IPV6
DNSAddresses
23
DNS server addresses in preference order, IPV6
DNSSearch
24
DNS search list, DOMAIN
NISServers
27
NIS server addresses in preference order, IPV6
NISDomain
29
NIS domain name, DOMAIN
SNTPServers
31
IPV6
InfoRefresh
32
UNUMBER32
BCMCDomain
33
Broadcast/multicast control server name list, DOMAIN
BCMCAddresses
34
Broadcast/multicast control server addresses, IPV6

Examples

Example 1 Altering the DHCP inittab File

In general, the DHCP inittab file should only be altered to add SITE options. If other options are added, they will not be automatically carried forward when the system is upgraded. For instance:

ipPairs    SITE, 132, IP, 2, 0, sdmi

describes an option named ipPairs, that is in the SITE category. That is, it is defined by each individual site, and is option code 132, which is of type IP Address, consisting of a potentially infinite number of pairs of IP addresses.

Files

  • /etc/dhcp/inittab
  • /etc/dhcp/inittabv6

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/network
Interface Stability
Committed

See Also

dhcpinfo(1), isspace(3C), attributes(7), dhcp(7), dhcpagent(8)

Alexander, S., and R. Droms. RFC 2132, DHCP Options and BOOTP Vendor Extensions. Network Working Group. March 1997.

Droms, R. RFC 2131, Dynamic Host Configuration Protocol. Network Working Group. March 1997.

Droms, R. RFC 3315, Dynamic Host Configuration Protocol for IPv6 (DHCPv6). Cisco Systems. July 2003.

Schulzrinne, H., and B. Volz. RFC 3319, Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation Protocol (SIP) Servers. Columbia University and Ericsson. July 2003.

Lemon, T., and S. Cheshire. RFC 3396, Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4). Network Working Group. November 2002.

Lemon, T., S. Cheshire, and B. Volz. RFC 3442, The Classless Static Route Option for Dynamic Host Configuration Protocol (DHCP) version 4. Network Working Group. December 2002.

Droms, R. RFC 3646, DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6). Cisco Systems. December 2003.

Kalusivalingam, V. RFC 3898, Network Information Service (NIS) Configuration Options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6). Cisco Systems. October 2004.

Chowdhury, K., P. Yegani, and L. Madour. RFC 4280, Dynamic Host Configuration Protocol (DHCP) Options for Broadcast and Multicast Control Servers. Starent Networks, Cisco Systems, and Ericsson. November 2005.

Mockapetris, P.V. RFC 1035, Domain names - implementation and specification. ISI. November 1987.