Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages

RedHat 9 (Linux i386) - man page for dhcp-options (redhat section 5)

dhcpd-options(5)		       File Formats Manual			 dhcpd-options(5)

NAME
       dhcp-options - Dynamic Host Configuration Protocol options

DESCRIPTION
       The Dynamic Host Configuration protocol allows the client to receive options from the DHCP
       server describing the network configuration and various services that are available on the
       network.    When  configuring  dhcpd(8)	or  dhclient(8) , options must often be declared.
       The syntax for declaring options, and the names and formats of the  options  that  can  be
       declared, are documented here.

REFERENCE: OPTION STATEMENTS
       DHCP  option  statements always start with the option keyword, followed by an option name,
       followed by option data.  The option names and data formats are described below.    It  is
       not  necessary  to  exhaustively  specify  all DHCP options - only those options which are
       needed by clients must be specified.

       Option data comes in a variety of formats, as defined below:

       The ip-address data  type  can  be  entered  either  as	an  explicit  IP  address  (e.g.,
       239.254.197.10)	or as a domain name (e.g., haagen.isc.org).  When entering a domain name,
       be sure that that domain name resolves to a single IP address.

       The int32 data type specifies a signed 32-bit integer.	The uint32 data type specifies an
       unsigned  32-bit  integer.    The  int16 and uint16 data types specify signed and unsigned
       16-bit integers.   The int8 and uint8 data types specify signed and unsigned  8-bit  inte-
       gers.  Unsigned 8-bit integers are also sometimes referred to as octets.

       The  text data type specifies an NVT ASCII string, which must be enclosed in double quotes
       - for example, to specify a root-path option, the syntax would be

       option root-path "10.0.1.4:/var/tmp/rootfs";

       The domain-name data type specifies a domain name,  which  must	not  enclosed  in  double
       quotes.	  This	data type is not used for any existing DHCP options.   The domain name is
       stored just as if it were a text option.

       The flag data type specifies a boolean value.   Booleans can be either true or  false  (or
       on or off, if that makes more sense to you).

       The  string data type specifies either an NVT ASCII string enclosed in double quotes, or a
       series of octets specified in hexadecimal, seperated by colons.	 For example:

	 option dhcp-client-identifier "CLIENT-FOO";
       or
	 option dhcp-client-identifier 43:4c:49:45:54:2d:46:4f:4f;

SETTING OPTION VALUES USING EXPRESSIONS
       Sometimes it's helpful to be able to set the value of a DHCP option based  on  some  value
       that  the  client  has  sent.   To do this, you can use expression evaluation.	The dhcp-
       eval(5) manual page describes how to write expressions.	 To assign the result of an eval-
       uation to an option, define the option as follows:

	 option my-option = expression ;

       For example:

	 option hostname = binary-to-ascii (16, 8, "-",
					    substring (hardware, 1, 6));

STANDARD DHCP OPTIONS
       The  documentation  for	the various options mentioned below is taken from the latest IETF
       draft document on DHCP options.	Options not listed below may not yet be implemented,  but
       it is possible to use such options by defining them in the configuration file.  Please see
       the DEFINING NEW OPTIONS heading later in this document for more information.

       The standard options are:

       option all-subnets-local flag;

	 This option specifies whether or not the client may assume that all subnets  of  the  IP
	 network  to which the client is connected use the same MTU as the subnet of that network
	 to which the client is directly connected.  A value of true indicates that  all  subnets
	 share the same MTU.  A value of false means that the client should assume that some sub-
	 nets of the directly connected network may have smaller MTUs.

       option arp-cache-timeout uint32;

	 This option specifies the timeout in seconds for ARP cache entries.

       option bootfile-name text;

	 This option is used to identify a bootstrap file.  If supported by the client, it should
	 have the same effect as the filename declaration.  BOOTP clients are unlikely to support
	 this option.  Some DHCP clients will support it, and others actually require it.

       option boot-size uint16;

	 This option specifies the length in 512-octet blocks of the default boot image  for  the
	 client.

       option broadcast-address ip-address;

	 This option specifies the broadcast address in use on the client's subnet.  Legal values
	 for broadcast addresses are specified in section 3.2.1.3 of STD 3 (RFC1122).

       option cookie-servers ip-address [, ip-address...  ];

	 The cookie server option specifies a list of RFC 865 cookie  servers  available  to  the
	 client.  Servers should be listed in order of preference.

       option default-ip-ttl uint8;

	 This  option  specifies  the default time-to-live that the client should use on outgoing
	 datagrams.

       option default-tcp-ttl uint8;

	 This option specifies the default TTL that the client should use when sending	TCP  seg-
	 ments.  The minimum value is 1.

       option dhcp-client-identifier string;

	 This  option  can be used to specify the a DHCP client identifier in a host declaration,
	 so that dhcpd can find the host record by matching against the client identifier.

	 Please be aware that some DHCP clients, when configured with client identifiers that are
	 ASCII text, will prepend a zero to the ASCII text.   So you may need to write:

	      option dhcp-client-identifier "\0foo";

	 rather than:

	      option dhcp-client-identifier "foo";

       option dhcp-max-message-size uint16;

	 This  option,	when  sent by the client, specifies the maximum size of any response that
	 the server sends to the client.   When specified on the server, if the  client  did  not
	 send  a  dhcp-max-message-size  option, the size specified on the server is used.   This
	 works for BOOTP as well as DHCP responses.

       option dhcp-parameter-request-list uint16;

	 This option, when sent by the client, specifies which	options  the  client  wishes  the
	 server  to  return.	Normally,  in the ISC DHCP client, this is done using the request
	 statement.   If this option is not specified by the client, the DHCP  server  will  nor-
	 mally	return	every  option that is valid in scope and that fits into the reply.   When
	 this option is specified on the server, the server returns the specified options.   This
	 can  be used to force a client to take options that it hasn't requested, and it can also
	 be used to tailor the response of the DHCP server for clients that may need a more  lim-
	 ited set of options than those the server would normally return.

       option domain-name text;

	 This  option  specifies  the domain name that client should use when resolving hostnames
	 via the Domain Name System.

       option domain-name-servers ip-address [, ip-address...  ];

	 The domain-name-servers option specifies a list of Domain Name System (STD 13, RFC 1035)
	 name servers available to the client.	Servers should be listed in order of preference.

       option extensions-path-name text;

	 This option specifies the name of a file containing additional options to be interpreted
	 according to the DHCP option format as specified in RFC2132.

       option finger-server ip-address [, ip-address... ];

	 The Finger server option specifies a list of Finger available to  the	client.   Servers
	 should be listed in order of preference.

       option font-servers ip-address [, ip-address...	];

	 This  option  specifies  a list of X Window System Font servers available to the client.
	 Servers should be listed in order of preference.

       option host-name string;

	 This option specifies the name of the client.	The name may or may not be qualified with
	 the  local  domain  name  (it is preferable to use the domain-name option to specify the
	 domain name).	See RFC 1035 for character set restrictions.

       option ieee802-3-encapsulation flag;

	 This option specifies whether or not the client should use Ethernet Version 2 (RFC  894)
	 or  IEEE  802.3  (RFC	1042)  encapsulation if the interface is an Ethernet.  A value of
	 false indicates that the client should use RFC 894 encapsulation.  A value of true means
	 that the client should use RFC 1042 encapsulation.

       option ien116-name-servers ip-address [, ip-address...  ];

	 The ien116-name-servers option specifies a list of IEN 116 name servers available to the
	 client.  Servers should be listed in order of preference.

       option impress-servers ip-address [, ip-address...  ];

	 The impress-server option specifies a list of Imagen Impress servers  available  to  the
	 client.  Servers should be listed in order of preference.

       option interface-mtu uint16;

	 This  option  specifies  the MTU to use on this interface.   The minimum legal value for
	 the MTU is 68.

       option ip-forwarding flag;

	 This option specifies whether the client should configure its IP layer for  packet  for-
	 warding.  A value of false means disable IP forwarding, and a value of true means enable
	 IP forwarding.

       option irc-server ip-address [, ip-address... ];

	 The IRC server option specifies a list of IRC available to the client.   Servers  should
	 be listed in order of preference.

       option log-servers ip-address [, ip-address...  ];

	 The  log-server  option  specifies  a	list  of MIT-LCS UDP log servers available to the
	 client.  Servers should be listed in order of preference.

       option lpr-servers ip-address  [, ip-address...	];

	 The LPR server option specifies a list of RFC 1179 line printer servers available to the
	 client.  Servers should be listed in order of preference.

       option mask-supplier flag;

	 This  option  specifies whether or not the client should respond to subnet mask requests
	 using ICMP.  A value of false indicates that the client should not respond.  A value  of
	 true means that the client should respond.

       option max-dgram-reassembly uint16;

	 This  option  specifies  the maximum size datagram that the client should be prepared to
	 reassemble.  The minimum value legal value is 576.

       option merit-dump text;

	 This option specifies the path-name of a file to which the client's core image should be
	 dumped  in  the  event  the client crashes.  The path is formatted as a character string
	 consisting of characters from the NVT ASCII character set.

       option mobile-ip-home-agent ip-address [, ip-address... ];

	 This option specifies a list of IP addresses indicating mobile IP home agents	available
	 to  the client.  Agents should be listed in order of preference, although normally there
	 will be only one such agent.

       option nds-context string;

	 The nds-context option specifies the name of the initial Netware Directory  Service  for
	 an NDS client.

       option nds-servers ip-address [, ip-address... ];

	 The nds-servers option specifies a list of IP addresses of NDS servers.

       option nds-tree-name string;

	 The nds-context option specifies NDS tree name that the NDS client should use.

       option netbios-dd-server ip-address [, ip-address...  ];

	 The NetBIOS datagram distribution server (NBDD) option specifies a list of RFC 1001/1002
	 NBDD servers listed in order of preference.

       option netbios-name-servers ip-address [, ip-address...];

	 The NetBIOS name server (NBNS) option specifies  a  list  of  RFC  1001/1002  NBNS  name
	 servers listed in order of preference.   NetBIOS Name Service is currently more commonly
	 referred to as WINS.	WINS servers can  be  specified  using	the  netbios-name-servers
	 option.

       option netbios-node-type uint8;

	 The  NetBIOS  node type option allows NetBIOS over TCP/IP clients which are configurable
	 to be configured as described in RFC 1001/1002.  The value  is  specified  as	a  single
	 octet which identifies the client type.

	 Possible node types are:

	 1    B-node: Broadcast - no WINS

	 2    P-node: Peer - WINS only.

	 4    M-node: Mixed - broadcast, then WINS

	 8    H-node: Hybrid - WINS, then broadcast

       option netbios-scope string;

	 The  NetBIOS  scope  option  specifies  the  NetBIOS over TCP/IP scope parameter for the
	 client as specified in RFC 1001/1002. See RFC1001, RFC1002, and RFC1035  for  character-
	 set restrictions.

       option nwip-domain string;

	 The name of the NetWare/IP domain that a NetWare/IP client should use.

       option nwip-suboptions string;

	 A  sequence  of  suboptions for NetWare/IP clients - see RFC2242 for details.	 Normally
	 this option is set by specifying specific NetWare/IP suboptions  -  see  the  NETWARE/IP
	 SUBOPTIONS section for more information.

       option nis-domain text;

	 This  option  specifies  the name of the client's NIS (Sun Network Information Services)
	 domain.  The domain is formatted as a character string consisting of characters from the
	 NVT ASCII character set.

       option nis-servers ip-address [, ip-address...  ];

	 This  option  specifies  a  list of IP addresses indicating NIS servers available to the
	 client.  Servers should be listed in order of preference.

       option nisplus-domain text;

	 This option specifies the name of the client's NIS+ domain.  The domain is formatted  as
	 a character string consisting of characters from the NVT ASCII character set.

       option nisplus-servers ip-address [, ip-address...  ];

	 This  option  specifies  a list of IP addresses indicating NIS+ servers available to the
	 client.  Servers should be listed in order of preference.

       option nntp-server ip-address [, ip-address... ];

	 The NNTP server option specifies a list of NNTP available to the client.  Servers should
	 be listed in order of preference.

       option non-local-source-routing flag;

	 This option specifies whether the client should configure its IP layer to allow forward-
	 ing of datagrams with non-local source routes (see Section 3.3.5 of [4] for a discussion
	 of  this  topic).  A value of 0 means disallow forwarding of such datagrams, and a value
	 of true means allow forwarding.

       option ntp-servers ip-address [, ip-address...  ];

	 This option specifies a list of IP addresses indicating NTP (RFC 1035) servers available
	 to the client.  Servers should be listed in order of preference.

       option path-mtu-aging-timeout uint32;

	 This option specifies the timeout (in seconds) to use when aging Path MTU values discov-
	 ered by the mechanism defined in RFC 1191.

       option path-mtu-plateau-table uint16 [, uint16...  ];

	 This option specifies a table of MTU sizes to use when performing Path MTU Discovery  as
	 defined  in  RFC  1191.   The	table is formatted as a list of 16-bit unsigned integers,
	 ordered from smallest to largest.  The minimum MTU value cannot be smaller than 68.

       option perform-mask-discovery flag;

	 This option specifies whether or not the client should  perform  subnet  mask	discovery
	 using	ICMP.  A value of false indicates that the client should not perform mask discov-
	 ery.  A value of true means that the client should perform mask discovery.

       option policy-filter ip-address ip-address
			 [, ip-address ip-address...];

	 This option specifies policy filters for non-local source routing.  The filters  consist
	 of  a	list of IP addresses and masks which specify destination/mask pairs with which to
	 filter incoming source routes.

	 Any source routed datagram whose next-hop address does not  match  one  of  the  filters
	 should be discarded by the client.

	 See STD 3 (RFC1122) for further information.

       option pop-server ip-address [, ip-address... ];

	 The POP3 server option specifies a list of POP3 available to the client.  Servers should
	 be listed in order of preference.

       option resource-location-servers ip-address
				     [, ip-address...];

	 This option specifies a list of RFC 887  Resource  Location  servers  available  to  the
	 client.  Servers should be listed in order of preference.

       option root-path text;

	 This  option  specifies the path-name that contains the client's root disk.  The path is
	 formatted as a character string consisting of characters from the  NVT  ASCII	character
	 set.

       option router-discovery flag;

	 This  option specifies whether or not the client should solicit routers using the Router
	 Discovery mechanism defined in RFC 1256.  A value of false  indicates	that  the  client
	 should  not perform router discovery.	A value of true means that the client should per-
	 form router discovery.

       option router-solicitation-address ip-address;

	 This option specifies the address to which the client should transmit	router	solicita-
	 tion requests.

       option routers ip-address [, ip-address...  ];

	 The  routers option specifies a list of IP addresses for routers on the client's subnet.
	 Routers should be listed in order of preference.

       option slp-directory-agent boolean ip-address [, ip-address... ];

	 This option specifies two things: the IP addresses of one or more Service Location  Pro-
	 tocol	Directory  Agents,  and whether the use of these addresses is mandatory.   If the
	 initial boolean value is true, the SLP agent should just use  the  IP	addresses  given.
	 If  the  value  is  false, the SLP agent may additionally do active or passive multicast
	 discovery of SLP agents (see RFC2165 for details).

	 Please note that in this option and the slp-service-scope option, the term  "SLP  Agent"
	 is being used to refer to a Service Location Protocol agent running on a machine that is
	 being configured using the DHCP protocol.

	 Also, please be aware that some companies may refer to SLP as NDS.  If you have  an  NDS
	 directory  agent  whose  address  you	need to configure, the slp-directory-agent option
	 should work.

       option slp-service-scope boolean text;

	 The Service Location Protocol Service Scope Option specifies two things: a list of  ser-
	 vice  scopes  for  SLP,  and  whether the use of this list is mandatory.  If the initial
	 boolean value is true, the SLP agent should only use the list of scopes provided in this
	 option;  otherwise,  it  may  use its own static configuration in preference to the list
	 provided in this option.

	 The text string should be a comma-seperated list of scopes that  the  SLP  agent  should
	 use.	 It  may  be omitted, in which case the SLP Agent will use the aggregated list of
	 scopes of all directory agents known to the SLP agent.

       option smtp-server ip-address [, ip-address... ];

	 The SMTP server option specifies a  list  of  SMTP  servers  available  to  the  client.
	 Servers should be listed in order of preference.

       option static-routes ip-address ip-address
			 [, ip-address ip-address...];

	 This  option  specifies  a  list  of static routes that the client should install in its
	 routing cache.  If multiple routes to the  same  destination  are  specified,	they  are
	 listed in descending order of priority.

	 The  routes consist of a list of IP address pairs.  The first address is the destination
	 address, and the second address is the router for the destination.

	 The default route (0.0.0.0) is an illegal destination for a static  route.   To  specify
	 the  default  route, use the routers option.	Also, please note that this option is not
	 intended for classless IP routing - it does not include a subnet mask.   Since classless
	 IP  routing  is  now the most widely deployed routing standard, this option is virtually
	 useless, and is not implemented by any of the popular DHCP clients, for example the  Mi-
	 crosoft DHCP client.

       option streettalk-directory-assistance-server ip-address
						  [, ip-address...];

	 The  StreetTalk  Directory  Assistance  (STDA)  server  option  specifies a list of STDA
	 servers available to the client.  Servers should be listed in order of preference.

       option streettalk-server ip-address [, ip-address... ];

	 The StreetTalk server option specifies a list of StreetTalk  servers  available  to  the
	 client.  Servers should be listed in order of preference.

       option subnet-mask ip-address;

	 The  subnet mask option specifies the client's subnet mask as per RFC 950.  If no subnet
	 mask option is provided anywhere in scope, as a last resort dhcpd will  use  the  subnet
	 mask  from the subnet declaration for the network on which an address is being assigned.
	 However, any subnet-mask option declaration that is  in  scope  for  the  address  being
	 assigned will override the subnet mask specified in the subnet declaration.

       option swap-server ip-address;

	 This specifies the IP address of the client's swap server.

       option tcp-keepalive-garbage flag;

	 This  option  specifies the whether or not the client should send TCP keepalive messages
	 with a octet of garbage for compatibility with older implementations.	A value of  false
	 indicates  that  a  garbage  octet  should not be sent. A value of true indicates that a
	 garbage octet should be sent.

       option tcp-keepalive-interval uint32;

	 This option specifies the interval (in seconds) that the client TCP should  wait  before
	 sending  a  keepalive	message  on  a TCP connection.	The time is specified as a 32-bit
	 unsigned integer.  A value of	zero  indicates  that  the  client  should  not  generate
	 keepalive messages on connections unless specifically requested by an application.

       option tftp-server-name text;

	 This  option  is  used to identify a TFTP server and, if supported by the client, should
	 have the same effect as the server-name declaration.	BOOTP  clients	are  unlikely  to
	 support this option.  Some DHCP clients will support it, and others actually require it.

       option time-offset int32;

	 The time-offset option specifies the offset of the client's subnet in seconds from Coor-
	 dinated Universal Time (UTC).

       option time-servers ip-address [, ip-address...	];

	 The time-server option specifies a list of RFC 868 time servers available to the client.
	 Servers should be listed in order of preference.

       option trailer-encapsulation flag;

	 This  option  specifies  whether  or not the client should negotiate the use of trailers
	 (RFC 893 [14]) when using the ARP protocol.  A value of  0  indicates	that  the  client
	 should  not  attempt  to  use	trailers.   A  value of true means that the client should
	 attempt to use trailers.

       option uap-servers text;

	 This option specifies a list of URLs, each pointing to  a  user  authentication  service
	 that is capable of processing authentication requests encapsulated in the User Authenti-
	 cation Protocol (UAP).  UAP servers can accept either HTTP 1.1 or SSLv3 connections.  If
	 the  list includes a URL that does not contain a port component, the normal default port
	 is assumed (i.e., port 80 for http and port 443 for https).  If the list includes a  URL
	 that does not contain a path component, the path /uap is assumed.   If more than one URL
	 is specified in this list, the URLs are seperated by spaces.

       option user-class string;

	 This option is used by some DHCP clients as a	way  for  users  to  specify  identifying
	 information to the client.   This can be used in a similar way to the vendor-class-iden-
	 tifier option, but the value of the option is specified by the  user,	not  the  vendor.
	 Most  recent DHCP clients have a way in the user interface to specify the value for this
	 identifier, usually as a text string.

	 option vendor-class-identifier string;

	    This option is used by some DHCP clients to identify the vendor type and possibly the
	    configuration  of a DHCP client.  The information is a string of bytes whose contents
	    are specific to the vendor and are not specified in a standard.   To see what  vendor
	    class  identifier  a  clients  are	sending, you can write the following in your DHCP
	    server configuration file:

	    set vendor-class option vendor-class-identifier;

	    This will result in all entries in the DHCP server lease database  file  for  clients
	    that sent vendor-class-identifier options having a set statement that looks something
	    like this:

	    set vendor-class "SUNW.Ultra-5_10";

	    The vendor-class-identifier option is normally used by the DHCP server  to	determine
	    the options that are returned in the vendor-encapsulated-options option.   Please see
	    the VENDOR ENCAPSULATED OPTIONS section of the dhcpd.conf  manual  page  for  further
	    information.

	 option vendor-encapsulated-options string;

	    The  vendor-encapsulated-options  option  can contain either a single vendor-specific
	    value or one or more vendor-specific suboptions.   This option is not normally speci-
	    fied  in  the DHCP server configuration file - instead, a vendor class is defined for
	    each vendor, vendor class suboptions are defined, values  for  those  suboptions  are
	    defined, and the DHCP server makes up a response on that basis.

	    Some  default behaviours for well-known DHCP client vendors (currently, the Microsoft
	    Windows 2000 DHCP client) are configured automatically, but otherwise  this  must  be
	    configured	manually  - see the VENDOR ENCAPSULATED OPTIONS section of the dhcpd.conf
	    manual page for details.

	 option x-display-manager ip-address [, ip-address...  ];

	    This option specifies a list of systems that are running the X Window System  Display
	    Manager  and  are  available  to  the client.  Addresses should be listed in order of
	    preference.

	 option www-server ip-address [, ip-address... ];

	    The WWW server option specifies a list of  WWW  available  to  the	client.   Servers
	    should be listed in order of preference.

RELAY AGENT INFORMATION OPTION
       An  IETF  draft,  draft-ietf-dhc-agent-options-11.txt,  defines	a  series of encapsulated
       options that a relay agent can add to a DHCP packet when relaying it to the  DHCP  server.
       The  server  can  then  make  address allocation decisions (or whatever other decisions it
       wants) based on these options.	The server also returns these options in any  replies  it
       sends  through  the  relay agent, so that the relay agent can use the information in these
       options for delivery or accounting purposes.

       The current draft defines two options.	To reference these options in  the  dhcp  server,
       specify the option space name, "agent", followed by a period, followed by the option name.
       It is not normally useful to define values for these options in the server, although it is
       permissible.   These options are not supported in the client.

       option agent.circuit-id string;

	 The  circuit-id  suboption encodes an agent-local identifier of the circuit from which a
	 DHCP client-to-server packet was received.  It is intended for use by agents in relaying
	 DHCP  responses  back	to  the  proper circuit.   The format of this option is currently
	 defined to be vendor-dependent, and will probably remain that way, although the  current
	 draft allows for for the possibility of standardizing the format in the future.

       option agent.remote-id string;

	 The  remote-id  suboption  encodes  information  about the remote host end of a circuit.
	 Examples of what it might contain include caller ID information,  username  information,
	 remote  ATM  address, cable modem ID, and similar things.   In principal, the meaning is
	 not well-specified, and it should generally be assumed to be an opaque  object  that  is
	 administratively guaranteed to be unique to a particular remote end of a circuit.

THE CLIENT FQDN SUBOPTIONS
       The  Client  FQDN  option,  currently  defined  in the Internet Draft draft-ietf-dhc-fqdn-
       option-00.txt is not a standard yet, but is in sufficiently wide use already that we  have
       implemented  it.   Due to the complexity of the option format, we have implemented it as a
       suboption space rather than a single option.   In general this option should not  be  con-
       figured by the user - instead it should be used as part of an automatic DNS update system.

       option fqdn.no-client-update flag;

	 When  the  client  sends  this,  if  it is true, it means the client will not attempt to
	 update its A record.	When sent by the server to the client, it means that  the  client
	 should not update its own A record.

       option fqdn.server-update flag;

	 When  the client sends this to the server, it is requesting that the server update its A
	 record.   When sent by the server, it means that the server has updated (or is about  to
	 update) the client's A record.

       option fqdn.encoded flag;

	 If  true,  this  indicates that the domain name included in the option is encoded in DNS
	 wire format, rather than as plain ASCII text.	 The client normally sets this	to  false
	 if  it  doesn't  support  DNS wire format in the FQDN option.	 The server should always
	 send back the same value that the client sent.   When this value is set on the  configu-
	 ration side, it controls the format in which the fqdn.fqdn suboption is encoded.

       option fqdn.rcode1 flag;

       option fqdn.rcode1 flag;

	 These	options specify the result of the updates of the A and PTR records, respectively,
	 and are only sent by the DHCP server to the DHCP client.  The values of these fields are
	 those defined in the DNS protocol specification.

       option fqdn.fqdn text;

	 Specifies the domain name that the client wishes to use.   This can be a fully-qualified
	 domain name, or a single label.   If there is no trailing generally update that name  in
	 some locally-defined domain.

       If  you	wish  to use any of these suboptions, we strongly recommend that you refer to the
       Client FQDN option draft (or standard, when it becomes a  standard)  -  the  documentation
       here is sketchy and incomplete in comparison, and is just intended for reference by people
       who already understand the Client FQDN option specification.

THE NETWARE/IP SUBOPTIONS
       RFC2242 defines a set of encapsulated options for Novell NetWare/IP clients.  To use these
       options	in  the dhcp server, specify the option space name, "nwip", followed by a period,
       followed by the option name.  The following options can be specified:

       option nwip.nsq-broadcast flag;

	 If true, the client should use the NetWare Nearest Server Query to locate  a  NetWare/IP
	 server.    The  behaviour  of	the  Novell  client if this suboption is false, or is not
	 present, is not specified.

       option nwip.preferred-dss ip-address [, ip-address... ];

	 This suboption specifies a list of up to five IP addresses, each of which should be  the
	 IP address of a NetWare Domain SAP/RIP server (DSS).

       option nwip.nearest-nwip-server ip-address
				    [, ip-address...];

	 This  suboption specifies a list of up to five IP addresses, each of which should be the
	 IP address of a Nearest NetWare IP server.

       option nwip.autoretries uint8;

	 Specifies the number of times that a NetWare/IP client  should  attempt  to  communicate
	 with a given DSS server at startup.

       option nwip.autoretry-secs uint8;

	 Specifies  the  number  of  seconds that a Netware/IP client should wait between retries
	 when attempting to establish communications with a DSS server at startup.

       option nwip.nwip-1-1 uint8;

	 If true, the NetWare/IP client should	support  NetWare/IP  version  1.1  compatibility.
	 This is only needed if the client will be contacting Netware/IP version 1.1 servers.

       option nwip.primary-dss ip-address;

	 Specifies  the  IP  address  of the Primary Domain SAP/RIP Service server (DSS) for this
	 NetWare/IP domain.   The NetWare/IP administration utility uses this  value  as  Primary
	 DSS server when configuring a secondary DSS server.

DEFINING NEW OPTIONS
       The  Internet  Software Consortium DHCP client and server provide the capability to define
       new options.   Each DHCP option has a name, a code, and a structure.   The name is used by
       you  to refer to the option.   The code is a number, used by the DHCP server and client to
       refer to an option.   The structure describes what the contents of an option looks like.

       To define a new option, you need to choose a name for it that is not in use for some other
       option  - for example, you can't use "host-name" because the DHCP protocol already defines
       a host-name option, which is documented earlier in this manual page.   If an  option  name
       doesn't	appear	in this manual page, you can use it, but it's probably a good idea to put
       some kind of unique string at the beginning so you can be sure that future  options  don't
       take your name.	 For example, you might define an option, "local-host-name", feeling some
       confidence that no official DHCP option name will ever start with "local".

       Once you have chosen a name, you must choose a code.  For site-local  options,  all  codes
       between	128  and 254 are reserved for DHCP options, so you can pick any one of these.  In
       practice, some vendors have interpreted the protocol rather loosely and have  used  option
       code  values greater than 128 themselves.   There's no real way to avoid this problem, but
       it's not likely to cause too much trouble in practice.

       The structure of an option is simply the format in which the option  data  appears.    The
       ISC  DHCP  server  currently supports a few simple types, like integers, booleans, strings
       and IP addresses, and it also supports the ability to define arrays  of	single	types  or
       arrays of fixed sequences of types.

       New options are declared as follows:

       option new-name code new-code = definition ;

       The  values of new-name and new-code should be the name you have chosen for the new option
       and the code you have chosen.   The definition should be the definition of  the	structure
       of the option.

       The following simple option type definitions are supported:

       BOOLEAN

       option new-name code new-code = boolean ;

       An  option  of type boolean is a flag with a value of either on or off (or true or false).
       So an example use of the boolean type would be:

       option use-zephyr code 180 = boolean;
       option use-zephyr on;

       INTEGER

       option new-name code new-code = sign integer width ;

       The sign token should either be blank, unsigned or signed.   The width can be either 8, 16
       or  32,	and  refers to the number of bits in the integer.   So for example, the following
       two lines show a definition of the sql-connection-max option and its use:

       option sql-connection-max code 192 = unsigned integer 16;
       option sql-connection-max 1536;

       IP-ADDRESS

       option new-name code new-code = ip-address ;

       An option whose structure is an IP address can be expressed either as a domain name or  as
       a dotted quad.  So the following is an example use of the ip-address type:

       option sql-server-address code 193 = ip-address;
       option sql-server-address sql.example.com;

       TEXT

       option new-name code new-code = text ;

       An option whose type is text will encode an ASCII text string.	For example:

       option sql-default-connection-name code 194 = text;
       option sql-default-connection-name "PRODZA";

       DATA STRING

       option new-name code new-code = string ;

       An  option  whose type is a data string is essentially just a collection of bytes, and can
       be specified either as quoted text, like the text type, or as a list of	hexadecimal  con-
       tents seperated by colons whose values must be between 0 and FF.   For example:

       option sql-identification-token code 195 = string;
       option sql-identification-token 17:23:19:a6:42:ea:99:7c:22;

       ENCAPSULATION

       option new-name code new-code = encapsulate identifier ;

       An  option  whose  type	is  encapsulate will encapsulate the contents of the option space
       specified in identifier.   Examples of encapsulated options in the  DHCP  protocol  as  it
       currently  exists  include  the vendor-encapsulated-options option, the netware-suboptions
       option and the relay-agent-information option.

       option space local;
       option local.demo code 1 = text;
       option local-encapsulation code 197 = encapsulate local;
       option local.demo "demo";

       ARRAYS

       Options can contain arrays of any of the above types except for the text and  data  string
       types,  which aren't currently supported in arrays.   An example of an array definition is
       as follows:

       option kerberos-servers code 200 = array of ip-address;
       option kerberos-servers 10.20.10.1, 10.20.11.1;

       RECORDS

       Options can also contain data structures consisting of a sequence of data types, which  is
       sometimes called a record type.	 For example:

       option contrived-001 code 201 = { boolean, integer 32, text };
       option contrived-001 on 1772 "contrivance";

       It's also possible to have options that are arrays of records, for example:

       option new-static-routes code 201 = array of {
	    ip-address, ip-address, ip-address, integer 8 };
       option static-routes
	    10.0.0.0 255.255.255.0 net-0-rtr.example.com 1,
	    10.0.1.0 255.255.255.0 net-1-rtr.example.com 1,
	    10.2.0.0 255.255.224.0 net-2-0-rtr.example.com 3;

VENDOR ENCAPSULATED OPTIONS
       The DHCP protocol defines the  vendor-encapsulated-options option, which allows vendors to
       define their own options that will be sent encapsulated in a standard DHCP  option.    The
       format  of the vendor-encapsulated-options option is either a series of bytes whose format
       is not specified, or a sequence of options, each of which consists of a	single-byte  ven-
       dor-specific  option  code, followed by a single-byte length, followed by as many bytes of
       data as are specified in the length (the length does not  include  itself  or  the  option
       code).

       The value of this option can be set in one of two ways.	 The first way is to simply spec-
       ify the data directly, using a text string or a colon-seperated list of	hexadecimal  val-
       ues.   For example:

       option vendor-encapsulated-options
	   2:4:AC:11:41:1:
	   3:12:73:75:6e:64:68:63:70:2d:73:65:72:76:65:72:31:37:2d:31:
	   4:12:2f:65:78:70:6f:72:74:2f:72:6f:6f:74:2f:69:38:36:70:63;

       The  second  way of setting the value of this option is to have the DHCP server generate a
       vendor-specific option buffer.	To do this, you must do four  things:  define  an  option
       space, define some options in that option space, provide values for them, and specify that
       that option space should be used to generate the vendor-encapsulated-options option.

       To define a new option space in which vendor options can be stored, use the  option  space
       statement:

       option space name ;

       The  name  can  then be used in option definitions, as described earlier in this document.
       For example:

       option space SUNW;
       option SUNW.server-address code 2 = ip-address;
       option SUNW.server-name code 3 = text;
       option SUNW.root-path code 4 = text;

       Once you have defined an option space and the format of	some  options,	you  can  set  up
       scopes that define values for those options, and you can say when to use them.	For exam-
       ple, suppose you want to handle two different classes of clients.   Using the option space
       definition  shown in the previous example, you can send different option values to differ-
       ent clients based on the vendor-class-identifier option that the clients send, as follows:

       class "vendor-classes" {
	 match option vendor-class-identifier;
       }

       option SUNW.server-address 172.17.65.1;
       option SUNW.server-name "sundhcp-server17-1";

       subclass "vendor-classes" "SUNW.Ultra-5_10" {
	 vendor-option-space SUNW;
	 option SUNW.root-path "/export/root/sparc";
       }

       subclass "vendor-classes" "SUNW.i86pc" {
	 vendor-option-space SUNW;
	 option SUNW.root-path "/export/root/i86pc";
       }

       As you can see in the preceding example, regular scoping rules apply, so  you  can  define
       values  that are global in the global scope, and only define values that are specific to a
       particular class in the local scope.   The vendor-option-space declaration tells the  DHCP
       server  to  use	options  in  the  SUNW option space to construct the vendor-encapsulated-
       options option.

SEE ALSO
       dhcpd.conf(5), dhcpd.leases(5),	dhclient.conf(5),  dhcp-eval(5),  dhcpd(8),  dhclient(8),
       RFC2132, RFC2131, draft-ietf-dhc-agent-options-??.txt.

AUTHOR
       The  Internet  Software Consortium DHCP Distribution was written by Ted Lemon under a con-
       tract with Vixie Labs.  Funding for this project was provided through the  Internet  Soft-
       ware  Consortium.   Information	about  the  Internet  Software Consortium can be found at
       http://www.isc.org.

										 dhcpd-options(5)


All times are GMT -4. The time now is 01:00 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
UNIX.COM Login
Username:
Password:  
Show Password