dhcp_network(4) 						   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 table or file with the name dhcp_network.

       The  DHCP network tables can exist as ASCII text files, binary text files, or NIS+ tables, depending on the data store used. Since the for-
       mat 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 a network, there should be no dhcp_network file for that network. To set the DHCP server in  informational
       mode,  where  it  responds to INFORM messages but does not lease addresses on that network, create an empty dhcp_network file for that net-
       work. For normal operations, where the DHCP server both leases addresses and responds to INFORM packets, create a dhcp_network  file  using
       dhcpmgr(1M) or pntadm(1M) and populate 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 unique octet string value of the DHCP
		       Client Identifier Option (code 61) which identifies a DHCP client. In the absence of the DHCP Client Identifier Option, the
		       DHCP client is identified 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 are 0 - 9 and A-F. Entries with values of 00 are
		       freely available for dynamic allocation to requesting clients. BOOTP clients are identified by  the  concatenation  of  the
		       network's hardware type (as defined by RFC 1340, titled "Assigned Numbers") and the client's hardware address. For example,
		       the following BOOTP client has a hardware type of '01' (10mb ethernet) 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, 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
		       gethostbyname(3NSL).

       Lease	       This  numeric  field  holds  the entry's absolute lease expiration time, and is in seconds since January 1, 1970. It can be
		       decimal, or hexadecimal (if 0x prefixes number). The special value -1 is used to denote a permanent lease.

       Macro	       This ASCII text field contains the dhcptab macro name used  to  look  up  this  entry's	configuration  parameters  in  the
		       dhcptab(4) database.

       Comment	       This ASCII text field contains an optional comment.

   TREATISE ON LEASES
       This  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 consults 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 the client's lease as represented by the Lease 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 LeaseNeg symbol has not been
       included in the client's dhcptab parameters, then the client's requested lease extension is ignored, and the lease is set to  be  the  time
       remaining  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 param-
       eter.

       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 attribute:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWdhcsu 		   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       dhcpconfig(1M), dhcpmgr(1M), dhtadm(1M), in.dhcpd(1M), pntadm(1M), dhcptab(4), dhcp(5), dhcp_modules(5), attributes(5)

       Solaris DHCP Service Developer's Guide

       System Administration Guide: IP Services

       Reynolds, J. and J. Postel, Assigned Numbers, STD 2, RFC 1340, USC/Information Sciences Institute, July 1992.

SunOS 5.10							    5 Mar 2004							   dhcp_network(4)