1dhcp_network(4) File Formats dhcp_network(4)
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6 dhcp_network - DHCP network tables
7
9 The Dynamic Host Configuration Protocol (DHCP) network tables are used
10 to map the client identifiers of DHCP clients to IP addresses and the
11 associated configuration parameters of that address. One DHCP network
12 table exists for each network served by the DHCP server, and each table
13 is named using the network's IP address. There is no table or file with
14 the name dhcp_network.
15 The DHCP network tables can exist as ASCII text files, binary text
18 files, or NIS+ tables, depending on the data store used. Since the for‐
19 mat of the file could change, the preferred method of managing the DHCP
20 network tables is through the use of dhcpmgr(1M) or the pntadm(1M) com‐
21 mand.
22 The dhcp_network file is used as a policy mechanism for whether
25 in.dhcpd(1M) leases addresses on a given network. If the DHCP server is
26 not serving leases or information to a network, there should be no
27 dhcp_network file for that network. To set the DHCP server in informa‐
28 tional mode, where it responds to INFORM messages but does not lease
29 addresses on that network, create an empty dhcp_network file for that
30 network. For normal operations, where the DHCP server both leases
31 addresses and responds to INFORM packets, create a dhcp_network file
32 using dhcpmgr(1M) or pntadm(1M) and populate it with leasable
33 addresses.
34 The format of the records in a DHCP network table depends on the data
37 store used to maintain the table. However, an entry in a DHCP network
38 table must contain the following fields:
39 Client_ID The client identifier field, Client_ID, is an ASCII hexa‐
41 decimal representation of the unique octet string value
42 of the DHCP Client Identifier Option (code 61) which
43 identifies a DHCP client. In the absence of the DHCP
44 Client Identifier Option, the DHCP client is identified
45 using the form given below for BOOTP clients. The number
46 of characters in this field must be an even number, with
47 a maximum length of 64 characters. Valid characters are 0
48 - 9 and A-F. Entries with values of 00 are freely avail‐
49 able for dynamic allocation to requesting clients. BOOTP
50 clients are identified by the concatenation of the net‐
51 work's hardware type (as defined by RFC 1340, titled
52 "Assigned Numbers") and the client's hardware address.
53 For example, the following BOOTP client has a hardware
54 type of '01' (10mb ethernet) and a hardware address of
55 8:0:20:11:12:b7, so its client identifier would be:
56 010800201112B7
57 Flags The Flags field is a decimal value, the bit fields of
60 which can have a combination of the following values:
61 1 (PERMANENT) Evaluation of the Lease field is turned
63 off (lease is permanent). If this bit
64 is not set, Evaluation of the Lease
65 field is enabled and the Lease is
66 DYNAMIC.
67 2 (MANUAL) This entry has a manual client ID bind‐
70 ing (cannot be reclaimed by DHCP
71 server). Client will not be allocated
72 another address.
73 4 (UNUSABLE) When set, this value means that either
76 through ICMP echo or client DECLINE,
77 this address has been found to be unus‐
78 able. Can also be used by the network
79 administrator to prevent a certain
80 client from booting, if used in con‐
81 junction with the MANUAL flag.
82 8 (BOOTP) This entry is reserved for allocation
85 to BOOTP clients only.
86 Client_IP The Client_IP field holds the IP address for this entry.
90 This value must be unique in the database.
91 Server_IP This field holds the IP address of the DHCP server which
94 owns this client IP address, and thus is responsible for
95 initial allocation to a requesting client. On a multi-
96 homed DHCP server, this IP address must be the first
97 address returned by gethostbyname(3NSL).
98 Lease This numeric field holds the entry's absolute lease expi‐
101 ration time, and is in seconds since January 1, 1970. It
102 can be decimal, or hexadecimal (if 0x prefixes number).
103 The special value -1 is used to denote a permanent lease.
104 Macro This ASCII text field contains the dhcptab macro name
107 used to look up this entry's configuration parameters in
108 the dhcptab(4) database.
109 Comment This ASCII text field contains an optional comment.
112 TREATISE ON LEASES
115 This section describes how the DHCP/BOOTP server calculates a client's
116 configuration lease using information contained in the dhcptab(4) and
117 DHCP network tables. The server consults the LeaseTim and LeaseNeg sym‐
118 bols in the dhcptab, and the Flags and Lease fields of the chosen IP
119 address record in the DHCP network table.
120 The server first examines the Flags field for the identified DHCP net‐
123 work table record. If the PERMANENT flag is on, then the client's lease
124 is considered permanent.
125 If the PERMANENT flag is not on, the server checks if the client's
128 lease as represented by the Lease field in the network table record has
129 expired. If the lease is not expired, the server checks if the client
130 has requested a new lease. If the LeaseNeg symbol has not been included
131 in the client's dhcptab parameters, then the client's requested lease
132 extension is ignored, and the lease is set to be the time remaining as
133 shown by the Lease field. If the LeaseNeg symbol has been included,
134 then the server will extend the client's lease to the value it
135 requested if this requested lease is less than or equal to the current
136 time plus the value of the client's LeaseTim dhcptab parameter.
137 If the client's requested lease is greater than policy allows (value of
140 LeaseTim), then the client is given a lease equal to the current time
141 plus the value of LeaseTim. If LeaseTim is not set, then the default
142 LeaseTim value is one hour.
143 For more information about the dhcptab symbols, see dhcptab(4).
146
148 See attributes(5) for a description of the following attribute:
149 ┌─────────────────────────────┬─────────────────────────────┐
154 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
155 ├─────────────────────────────┼─────────────────────────────┤
156 │Availability │SUNWdhcsu │
157 ├─────────────────────────────┼─────────────────────────────┤
158 │Interface Stability │Evolving │
159 └─────────────────────────────┴─────────────────────────────┘
160
162 dhcpconfig(1M), dhcpmgr(1M), dhtadm(1M), in.dhcpd(1M), pntadm(1M),
163 dhcptab(4), dhcp(5), dhcp_modules(5), attributes(5)
164 Solaris DHCP Service Developer's Guide
167 System Administration Guide: IP Services
170 Reynolds, J. and J. Postel, Assigned Numbers, STD 2, RFC 1340,
173 USC/Information Sciences Institute, July 1992.
174SunOS 5.11 5 Mar 2004 dhcp_network(4)