path: root/usr/src/man/man4/dhcp_network.4

'\" te
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.TH dhcp_network 4 "5 Mar 2004" "SunOS 5.11" "File Formats"
.SH NAME
dhcp_network \- DHCP network tables
.SH DESCRIPTION
.sp
.LP
The Dynamic Host Configuration Protocol (\fBDHCP\fR) network tables are used to
map the client identifiers of \fBDHCP\fR clients to \fBIP\fR addresses and the
associated configuration parameters of that address. One \fBDHCP\fR network
table exists for each network served by the \fBDHCP\fR server, and each table
is named using the network's \fBIP\fR address. There is no table or file with
the name \fBdhcp_network\fR.
.sp
.LP
The \fBDHCP\fR network tables can exist as \fBASCII\fR text files, binary text
files, or \fBNIS+\fR tables, depending on the data store used. Since the format
of the file could change, the preferred method of managing the \fBDHCP\fR
network tables is through the use of \fBdhcpmgr\fR(1M) or the \fBpntadm\fR(1M)
command.
.sp
.LP
The \fBdhcp_network\fR file is used as a policy mechanism for whether
\fBin.dhcpd\fR(1M) leases addresses on a given network. If the \fBDHCP\fR
server is not serving leases or information to a network, there should be no
\fBdhcp_network\fR file for that network. To set the \fBDHCP\fR server in
\fBinformational\fR mode, where it responds to \fBINFORM\fR messages but does
not lease addresses on that network, create an empty \fBdhcp_network\fR file
for that network. For normal operations, where the \fBDHCP\fR server both
leases addresses and responds to \fBINFORM\fR packets, create a
\fBdhcp_network\fR file using \fBdhcpmgr\fR(1M) or \fBpntadm\fR(1M) and
populate it with leasable addresses.
.sp
.LP
The format of the records in a \fBDHCP\fR network table depends on the data
store used to maintain the table. However, an entry in a \fBDHCP\fR network
table must contain the following fields:
.sp
.ne 2
.mk
.na
\fB\fBClient_ID\fR \fR
.ad
.RS 14n
.rt  
The client identifier field, \fBClient_ID\fR, is an \fBASCII\fR hexadecimal
representation of the unique octet string value of the \fBDHCP\fR Client
Identifier Option (code 61) which identifies a \fBDHCP\fR client. In the
absence of the \fBDHCP\fR Client Identifier Option, the \fBDHCP\fR client is
identified using the form given below for \fBBOOTP\fR clients. The number of
characters in this field must be an even number, with a maximum length of 64
characters. Valid characters are \fB0\fR \fB-\fR \fB9\fR and \fBA\fR-\fBF\fR.
Entries with values of \fB00\fR are freely available for dynamic allocation to
requesting clients. \fBBOOTP\fR clients are identified by the concatenation of
the network's hardware type (as defined by \fBRFC\fR 1340, titled "Assigned
Numbers") and the client's hardware address. For example, the following
\fBBOOTP\fR client has a hardware type of '\fB01\fR' (10mb ethernet) and a
hardware address of \fB8:0:20:11:12:b7\fR, so its client identifier would be:
\fB010800201112B7\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fBFlags\fR \fR
.ad
.RS 14n
.rt  
The \fBFlags\fR field is a decimal value, the bit fields of which can have a
combination of the following values:
.sp
.ne 2
.mk
.na
\fB\fB1 (PERMANENT)\fR \fR
.ad
.RS 18n
.rt  
Evaluation of the \fBLease\fR field is turned off (lease is permanent). If this
bit is not set, Evaluation of the \fBLease\fR field is enabled and the
\fBLease\fR is \fBDYNAMIC.\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fB2 (MANUAL)\fR \fR
.ad
.RS 18n
.rt  
This entry has a manual client \fBID\fR binding (cannot be reclaimed by
\fBDHCP\fR server). Client will not be allocated another address.
.RE

.sp
.ne 2
.mk
.na
\fB\fB4 (UNUSABLE)\fR \fR
.ad
.RS 18n
.rt  
When set, this value means that either through \fBICMP\fR echo or client
\fBDECLINE,\fR this address has been found to be unusable. Can also be used by
the network administrator to \fIprevent\fR a certain client from booting, if
used in conjunction with the \fBMANUAL\fR flag.
.RE

.sp
.ne 2
.mk
.na
\fB\fB8 (BOOTP)\fR \fR
.ad
.RS 18n
.rt  
This entry is reserved for allocation to \fBBOOTP\fR clients only.
.RE

.RE

.sp
.ne 2
.mk
.na
\fB\fBClient_IP\fR \fR
.ad
.RS 14n
.rt  
The \fBClient_IP\fR field holds the \fBIP\fR address for this entry. This value
must be unique in the database.
.RE

.sp
.ne 2
.mk
.na
\fB\fBServer_IP\fR \fR
.ad
.RS 14n
.rt  
This field holds the \fBIP\fR address of the \fBDHCP\fR server which \fIowns\fR
this client \fBIP\fR address, and thus is responsible for initial allocation to
a requesting client. On a multi-homed DHCP server, this IP address must be the
first address returned by \fBgethostbyname\fR(3NSL).
.RE

.sp
.ne 2
.mk
.na
\fB\fBLease\fR \fR
.ad
.RS 14n
.rt  
This numeric field holds the entry's absolute lease expiration time, and is in
seconds since \fBJanuary 1, 1970\fR. It can be decimal, or hexadecimal (if
\fB0x\fR prefixes number). The special value \fB-1\fR is used to denote a
permanent lease.
.RE

.sp
.ne 2
.mk
.na
\fB\fBMacro\fR \fR
.ad
.RS 14n
.rt  
This \fBASCII\fR text field contains the \fBdhcptab\fR macro name used to look
up this entry's configuration parameters in the \fBdhcptab\fR(4) database.
.RE

.sp
.ne 2
.mk
.na
\fB\fBComment\fR \fR
.ad
.RS 14n
.rt  
This \fBASCII\fR text field contains an optional comment.
.RE

.SS "TREATISE ON LEASES"
.sp
.LP
This section describes how the \fBDHCP/BOOTP\fR server calculates a client's
configuration lease using information contained in the \fBdhcptab\fR(4) and
\fBDHCP\fR network tables. The server consults the \fBLeaseTim\fR and
\fBLeaseNeg\fR symbols in the \fBdhcptab\fR, and the \fBFlags\fR and
\fBLease\fR fields of the chosen IP address record in the \fBDHCP\fR network
table.
.sp
.LP
The server first examines the \fBFlags\fR field for the identified \fBDHCP\fR
network table record. If the \fBPERMANENT\fR flag is on, then the client's
lease is considered permanent.
.sp
.LP
If the \fBPERMANENT\fR flag is not on, the server checks if the client's lease
as represented by the \fBLease\fR field in the network table record has
expired. If the lease is not expired, the server checks if the client has
requested a new lease. If the \fBLeaseNeg\fR symbol has not been included in
the client's \fBdhcptab\fR parameters, then the client's requested lease
extension is ignored, and the lease is set to be the time remaining as shown by
the \fBLease\fR field. If the \fBLeaseNeg\fR symbol \fIhas\fR been included,
then the server will extend the client's lease to the value it requested if
this requested lease is less than or equal to the current time plus the value
of the client's \fBLeaseTim\fR \fBdhcptab\fR parameter.
.sp
.LP
If the client's requested lease is greater than policy allows (value of
\fBLeaseTim\fR), then the client is given a lease equal to the current time
plus the value of \fBLeaseTim\fR. If \fBLeaseTim\fR is not set, then the
default \fBLeaseTim\fR value is one hour.
.sp
.LP
For more information about the \fBdhcptab\fR symbols, see \fBdhcptab\fR(4).
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for a description of the following attribute:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityEvolving
.TE

.SH SEE ALSO
.sp
.LP
\fBdhcpconfig\fR(1M), \fBdhcpmgr\fR(1M), \fBdhtadm\fR(1M), \fBin.dhcpd\fR(1M),
\fBpntadm\fR(1M), \fBdhcptab\fR(4), \fBdhcp\fR(5), \fBdhcp_modules\fR(5),
\fBattributes\fR(5)
.sp
.LP
\fISolaris DHCP Service Developer\&'s Guide\fR
.sp
.LP
\fISystem Administration Guide: IP Services\fR
.sp
.LP
Reynolds, J. and J. Postel, \fIAssigned Numbers\fR, STD 2, RFC 1340,
USC/Information Sciences Institute, July 1992.