NAME

dhcptags − DHCP option mnemonic mapping table

DESCRIPTION

For the most part, parameters (henceforth referred to as options) returned to the client by the DHCP/BOOTP protocol are encoded in the so-called vendor field of the BOOTP packet.  Each option is identified numerically, and also carries a length specifier.  The purpose of dhcptags is to indentify the type of each option, to label each with a short mnemonic text string for use by dhcpinfo(1), and to give a longer textual description. 

OPTIONS

General Options

Options defined by DHCP are of three general types:

Standard All client and server DHCP implementations agree on the semantics.  These are administered by the Internet Naming Authority (IANA).  These options are numbered from 1 to 127. 

Site-specific Within a specific site, all client and server implementations agree as to 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. 

Vendor-specific Each vendor may define 256 options unique to that vendor.  The vendor is identified within a DHCP packet by the "Vendor Class" option (#60).  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 (#43); within a specific DHCP packet there may be several instances of option #43. 

Pseudo Options

As well as the three general types, the Solaris DHCP implementation defines certain "pseudo" options, numbered from 512 upward.  These are a convenient method for referring to items which either correspond to fixed fields in the BOOTP packet (such as the siaddr field) or which, though not options themselves, are used in constructing valid options (for example, the home directory used in constructing the exact path to a boot image). 

In general, the agent (see dhcpagent(1M)) knows little if anything about the semantics of any of the first three kinds of option, except for the subnet mask and broadcast address.  Its only duty is to acquire and store this data and to make it available to other interested parties (see dhcpinfo(1)).  The responsibility for understanding and using the data rests with these third parties.  Pseudo tags, on the contrary, have a specific meaning to dhcpagent(1M), and consequently it is meaningless to add to this list.  The only useful edit that can be performed on the pseudo tags is to change the textual description or the mnemonic. 

USAGE

Blank lines and those whose first non-whitespace character is ’#’ are ignored.  Data entries are written one per line and have five fields.  An individual entry cannot be continued onto another line. 

The fields are (in order):

• Tag number

• Mnemonic identifier

• Vendor class

• Data type

(One from the following case insensitive values):

byte

octet

int1 A 1-byte value

int2 A 2-byte value

int4 A 4-byte value

string A printable character string

ip An IP address

iplist A list of IP addresses

int2list A list of 2-byte values

opaque An array of 1-byte values

boolean Either true or false

• Long name

Standard Option List

FILES

/etc/dhcp/dhcptags

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

dhcpinfo(1), dhcpagent(1M), attributes(5)

Alexander, S., and R. Droms, DHCP Options and BOOTP Vendor Extensions, RFC 2132, Silicon Graphics, Inc., Bucknell University, March 1997.

Droms, R., Dynamic Host Configuration Protocol, RFC 2131, Bucknell University, March 1997.

SunOS 5.6  —  Last change:   —  Last change: