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DHCP-OPTIONS(5)		  FreeBSD File Formats Manual	       DHCP-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 for-
     mats 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).	 A
     domain name must resolve 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 integers.  Unsigned 8-bit
     integers are also sometimes referred to as	octets.

     The string	data type specifies an NVT (Network Virtual Terminal) ASCII
     string, which must	be enclosed in double quotes - for example, to specify
     a domain-name option, the syntax would be

	   option domain-name "isc.org";

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

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

     The documentation for the various options mentioned below is taken	from
     the IETF draft document on	DHCP options, RFC 2132.	 Options which are not
     listed by name may	be defined by the name option-nnn, where nnn is	the
     decimal number of the option code.	 These options may be followed either
     by	a string, enclosed in quotes, or by a series of	octets,	expressed as
     two-digit hexadecimal numbers separated by	colons.	 For example:

	   option option-133 "my-option-133-text";
	   option option-129 1:54:c9:2b:47;

     Because dhcpd(8) does not know the	format of these	undefined option
     codes, no checking	is done	to ensure the correctness of the entered data.

     The standard options are:

   RFC 1497 Vendor Extensions
     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(8) will use	the subnet mask	from the sub-
	     net 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 time-offset	int32;
	     The time-offset option specifies the offset of the	client's sub-
	     net in seconds from Coordinated Universal Time (UTC).

     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 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 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 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 log-servers	ip-address [, ip-address ...];
	     The log-servers option specifies a	list of	MIT-LCS	UDP log
	     servers available to the client.  Servers should be listed	in
	     order of preference.

     option cookie-servers ip-address [, ip-address ...];
	     The cookie-servers	option specifies a list	of RFC 865 cookie
	     servers available to the client.  Servers should be listed	in
	     order of preference.

     option lpr-servers	ip-address [, ip-address ...];
	     The lpr-servers option specifies a	list of	RFC 1179 line printer
	     servers available to the client.  Servers should be listed	in
	     order of preference.

     option impress-servers ip-address [, ip-address ...];
	     The impress-servers option	specifies a list of Imagen Impress
	     servers 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 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 boot-size uint16;
	     This option specifies the length in 512-octet blocks of the
	     default boot image	for the	client.

     option merit-dump string;
	     This option specifies the pathname	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 domain-name	string;
	     This option specifies the domain name that	the client should use
	     when resolving hostnames via the Domain Name System.

     option domain-search string;
	     This option specifies a list of domain names that the client
	     should use	when resolving hostnames via the Domain	Name System.
	     This option is defined in RFC 3397.

     option swap-server	ip-address;
	     This specifies the	IP address of the client's swap	server.

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

   IP Layer Parameters per Host
     option ip-forwarding flag;
	     This option specifies whether the client should configure its IP
	     layer for packet forwarding.  A value of 0	means disable IP for-
	     warding, and a value of 1 means enable IP forwarding.

     option non-local-source-routing flag;
	     This option specifies whether the client should configure its IP
	     layer to allow forwarding 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 1	means allow forwarding.

     option policy-filter ip-address ip-address	[, ip-address ip-address ...];
	     This option specifies policy filters for non-local	source rout-
	     ing.  The filters consist of a list of IP addresses and masks
	     which specify destination/mask pairs with which to	filter incom-
	     ing 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 (RFC 1122) for further information.

     option max-dgram-reassembly uint16;
	     This option specifies the maximum size datagram that the client
	     should be prepared	to reassemble.	The minimum legal value	is
	     576.

     option default-ip-ttl uint8;
	     This option specifies the default time-to-live that the client
	     should use	on outgoing datagrams.

     option path-mtu-aging-timeout uint32;
	     This option specifies the timeout (in seconds) to use when	aging
	     Path MTU values discovered	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 format-
	     ted as a list of 16-bit unsigned integers,	ordered	from smallest
	     to	largest.  The minimum MTU value	cannot be smaller than 68.

   IP Layer Parameters per Interface
     option interface-mtu uint16;
	     This option specifies the MTU to use on this interface.  The min-
	     imum legal	value for the MTU is 68.

     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 1 indicates that	all
	     subnets share the same MTU.  A value of 0 means that the client
	     should assume that	some subnets of	the directly connected network
	     may have smaller MTUs.

     option broadcast-address ip-address;
	     This option specifies the broadcast address in use	on the
	     client's subnet.  Legal values for	broadcast addresses are	speci-
	     fied in section 3.2.1.3 of	STD 3 (RFC 1122).

     option perform-mask-discovery flag;
	     This option specifies whether or not the client should perform
	     subnet mask discovery using ICMP.	A value	of 0 indicates that
	     the client	should not perform mask	discovery.  A value of 1 means
	     that the client should perform mask discovery.

     option mask-supplier flag;
	     This option specifies whether or not the client should respond to
	     subnet mask requests using	ICMP.  A value of 0 indicates that the
	     client should not respond.	 A value of 1 means that the client
	     should respond.

     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	0 indicates that the client should not perform router
	     discovery.	 A value of 1 means that the client should perform
	     router discovery.

     option router-solicitation-address	ip-address;
	     This option specifies the address to which	the client should
	     transmit router solicitation requests.

     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.

   Link	Layer Parameters per Interface
     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 1 means that	the client should attempt to
	     use trailers.

     option arp-cache-timeout uint32;
	     This option specifies the timeout in seconds for ARP cache
	     entries.

     option ieee802-3-encapsulation flag;
	     This option specifies whether or not the client should use	Ether-
	     net Version 2 (RFC	894) or	IEEE 802.3 (RFC	1042) encapsulation if
	     the interface is an Ethernet.  A value of 0 indicates that	the
	     client should use RFC 894 encapsulation.  A value of 1 means that
	     the client	should use RFC 1042 encapsulation.

   TCP Parameters
     option default-tcp-ttl uint8;
	     This option specifies the default TTL that	the client should use
	     when sending TCP segments.	 The minimum value is 1.

     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 con-
	     nection.  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 tcp-keepalive-garbage flag;
	     This option specifies whether or not the client should send TCP
	     keepalive messages	with an	octet of garbage for compatibility
	     with older	implementations.  A value of 0 indicates that a
	     garbage octet should not be sent.	A value	of 1 indicates that a
	     garbage octet should be sent.

   Application and Service Parameters
     option nis-domain string;
	     This option specifies the name of the client's NIS	(Sun Network
	     Information Services) domain.  The	domain is formatted as a char-
	     acter string consisting of	characters from	the NVT	ASCII charac-
	     ter 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 ntp-servers	ip-address [, ip-address ...];
	     This option specifies a list of IP	addresses indicating NTP (RFC
	     1305) servers available to	the client.  Servers should be 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.	 Net-
	     BIOS Name Service is currently more commonly referred to as WINS.
	     WINS servers can be specified using the netbios-name-servers
	     option.

     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 prefer-
	     ence.

     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	iden-
	     tifies 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 RFC
	     1001, RFC 1002, and RFC 1035 for character-set restrictions.

     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 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 dhcp-client-identifier data-string;
	     This option can be	used to	specify	a DHCP client identifier in a
	     host declaration, so that dhcpd(8)	can find the host record by
	     matching against the client identifier.

     option nisplus-domain string;
	     This option specifies the name of the client's NIS+ domain.  The
	     domain is formatted as a character	string consisting of charac-
	     ters 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 tftp-server-name string;
	     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 bootfile-name string;
	     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 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 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 pop-server ip-address [, ip-address	...];
	     The pop-server option specifies a list of POP3 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 servers available
	     to	the client.  Servers should be listed in order of preference.

     option www-server ip-address [, ip-address	...];
	     The www-server option specifies a list of WWW servers available
	     to	the client.  Servers should be listed in order of preference.

     option finger-server ip-address [,	ip-address ...];
	     The finger-server option specifies	a list of finger(1) servers
	     available to the client.  Servers should be listed	in order of
	     preference.

     option irc-server ip-address [, ip-address	...];
	     The irc-server option specifies a list of IRC 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 streettalk-directory-assistance-server ip-address [, ip-address
	     ...];
	     The StreetTalk Directory Assistance (STDA)	server option speci-
	     fies a list of STDA servers available to the client.  Servers
	     should be listed in order of preference.

SEE ALSO
     dhclient.conf(5), dhcpd.conf(5), dhcpd.leases(5), dhclient(8), dhcpd(8)

     RFC 2131, RFC 2132.

AUTHORS
     The dhcpd(8) utility was written by Ted Lemon <mellon@vix.com> under a
     contract with Vixie Labs.

     The current implementation	was reworked by	Henning	Brauer
     <henning@openbsd.org>.

FreeBSD	9.2			January	1, 1995			   FreeBSD 9.2

NAME | DESCRIPTION | REFERENCE: OPTION STATEMENTS | SEE ALSO | AUTHORS

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