File Formats dhcp_network(4)
NAME
dhcp_network - DHCP network tables
DESCRIPTION
The Dynamic Host Configuration Protocol (DHCP) network tables are used to map the client identifiers of DHCP clients to IP addresses and the associated configuration parameters of that address. One DHCP network table exists for each network served by the DHCP server, and each table is named using the network's IP address. There is no tableor file with the name dhcp_network.
The DHCP network tables can exist as ASCII text files or binary text files, depending on the data store used. Since the format of the file could change, the preferred method of managing the DHCP network tables is through the use of dhcpmgr(1M) or the pntadm(1M) command.The dhcp_network file is used as a policy mechanism for
whether in.dhcpd(1M) leases addresses on a given network. If the DHCP server is not serving leases or information to anetwork, there should be no dhcp_network file for that net-
work. To set the DHCP server in informational mode, where it responds to INFORM messages but does not lease addresses onthat network, create an empty dhcp_network file for that
network. For normal operations, where the DHCP server both leases addresses and responds to INFORM packets, create adhcp_network file using dhcpmgr(1M) or pntadm(1M) and popu-
late it with leasable addresses. The format of the records in a DHCP network table depends on the data store used to maintain the table. However, an entry in a DHCP network table must contain the following fields:Client_ID The client identifier field, Client_ID, is an
ASCII hexadecimal representation of the uniqueoctet string value of the DHCP Client Identif-
ier Option (code 61) which identifies a DHCP client. In the absence of the DHCP ClientIdentifier Option, the DHCP client is identi-
fied using the form given below for BOOTP clients. The number of characters in this field must be an even number, with a maximum length of 64 characters. Valid characters are0 - 9 and A-F. Entries with values of 00 are
freely available for dynamic allocation torequesting clients. BOOTP clients are identi-
fied by the concatenation of the network's hardware type (as defined by RFC 1340, titledSunOS 5.11 Last change: 10 Dec 2009 1
File Formats dhcp_network(4)
"Assigned Numbers") and the client's hardware address. For example, the following BOOTPclient has a hardware type of '01' (10mb eth-
ernet) and a hardware address of 8:0:20:11:12:b7, so its client identifier would be: 010800201112B7 Flags The Flags field is a decimal value, the bit fields of which can have a combination of the following values: 1 (PERMANENT) Evaluation of the Lease field is turned off (lease is permanent). If this bit is not set, Evaluation of the Lease field is enabled and the Lease is DYNAMIC. 2 (MANUAL) This entry has a manual client ID binding (cannot be reclaimed by DHCP server). Client will not be allocated another address. 4 (UNUSABLE) When set, this value means that either through ICMP echo or client DECLINE, this address has been found to be unusable. Can also be used by the network administrator to prevent a certain client from booting, if used in conjunction with the MANUAL flag. 8 (BOOTP) This entry is reserved for allocation to BOOTP clients only.Client_IP The Client_IP field holds the IP address for
this entry. This value must be unique in the database.Server_IP This field holds the IP address of the DHCP
server which owns this client IP address, andSunOS 5.11 Last change: 10 Dec 2009 2
File Formats dhcp_network(4)
thus is responsible for initial allocation toa requesting client. On a multi-homed DHCP
server, this IP address must be the first address returned by gethostbyname(3NSL). Lease This numeric field holds the entry's absolute lease expiration time, and is in seconds sinceJanuary 1, 1970. It can be decimal, or hexade-
cimal (if 0x prefixes number). The specialvalue -1 is used to denote a permanent lease.
Macro This ASCII text field contains the dhcptabmacro name used to look up this entry's confi-
guration parameters in the dhcptab(4) data-
base. Comment This ASCII text field contains an optional comment. TREATISE ON LEASESThis section describes how the DHCP/BOOTP server calculates a client's configuration lease using information contained
in the dhcptab(4) and DHCP network tables. The server con-
sults the LeaseTim and LeaseNeg symbols in the dhcptab, and the Flags and Lease fields of the chosen IP address record in the DHCP network table. The server first examines the Flags field for the identified DHCP network table record. If the PERMANENT flag is on, then the client's lease is considered permanent. If the PERMANENT flag is not on, the server checks if theclient's lease as represented by the Lease field in the net-
work table record has expired. If the lease is not expired, the server checks if the client has requested a new lease. If the LeaseNeg symbol has not been included in the client'sdhcptab parameters, then the client's requested lease exten-
sion is ignored, and the lease is set to be the time remain-
ing as shown by the Lease field. If the LeaseNeg symbol has 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 LeaseTim dhcptab parameter.SunOS 5.11 Last change: 10 Dec 2009 3
File Formats dhcp_network(4)
If the client's requested lease is greater than policy allows (value of LeaseTim), then the client is given a lease equal to the current time plus the value of LeaseTim. If LeaseTim is not set, then the default LeaseTim value is one hour. For more information about the dhcptab symbols, see dhcptab(4).ATTRIBUTES
See attributes(5) for a description of the following attri-
bute:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | service/network/dhcp ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
SEE ALSO
dhcpconfig(1M), dhcpmgr(1M), dhtadm(1M), in.dhcpd(1M),pntadm(1M), dhcptab(4), dhcp(5), dhcp_modules(5), attri-
butes(5) Oracle Solaris DHCP Service Developer's Guide System Administration Guide: IP Services Reynolds, J. and J. Postel, Assigned Numbers, STD 2, RFC1340, USC/Information Sciences Institute, July 1992.
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