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OpenSolaris 2009.06 - man page for dhcp_network (opensolaris section 4)

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dhcp_network(4) 			   File Formats 			  dhcp_network(4)

       dhcp_network - DHCP network tables

       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 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 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 network. 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  main-
       tain  the  table.  However,  an	entry  in a DHCP network table must contain the following

       Client_ID     The client identifier field, Client_ID, is an ASCII hexadecimal  representa-
		     tion  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  alloca-
		     tion  to  requesting clients. BOOTP clients are identified by the concatena-
		     tion of the  network's  hardware  type  (as  defined  by  RFC  1340,  titled
		     "Assigned Numbers") and the client's hardware address. For example, the fol-
		     lowing BOOTP client has a hardware type of '01' (10mb ethernet) and a  hard-
		     ware  address  of	8:0:20:11:12:b7,  so  its  client  identifier  would  be:

       Flags	     The Flags field is a decimal value, the bit fields of which can have a  com-
		     bination of the following values:

		     1 (PERMANENT)     Evaluation of the Lease field is turned off (lease is per-
				       manent). 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 unus-
				       able.  Can  also  be  used by the network administrator to
				       prevent a certain client from booting, if used in conjunc-
				       tion with the MANUAL flag.

		     8 (BOOTP)	       This  entry  is	reserved  for allocation to BOOTP clients

       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.

       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 parameter.

       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).

       See attributes(5) for a description of the following attribute:

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

       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 5.11				    5 Mar 2004				  dhcp_network(4)
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