rfc2132.txt

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   +-----+-----+-----+
   |  29 |  1  | 0/1 |
   +-----+-----+-----+

5.5. Mask Supplier Option

   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.

   The code for this option is 30, and its length is 1.

    Code   Len  Value
   +-----+-----+-----+
   |  30 |  1  | 0/1 |
   +-----+-----+-----+




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RFC 2132        DHCP Options and BOOTP Vendor Extensions      March 1997


5.6. Perform Router Discovery Option

   This option specifies whether or not the client should solicit
   routers using the Router Discovery mechanism defined in RFC 1256
   [13].  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.

   The code for this option is 31, and its length is 1.

    Code   Len  Value
   +-----+-----+-----+
   |  31 |  1  | 0/1 |
   +-----+-----+-----+

5.7. Router Solicitation Address Option

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

   The code for this option is 32, and its length is 4.

    Code   Len            Address
   +-----+-----+-----+-----+-----+-----+
   |  32 |  4  |  a1 |  a2 |  a3 |  a4 |
   +-----+-----+-----+-----+-----+-----+

5.8. Static Route Option

   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.  See section 3.5 for information about the router option.

   The code for this option is 33.  The minimum length of this option is
   8, and the length MUST be a multiple of 8.








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    Code   Len         Destination 1           Router 1
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
   |  33 |  n  |  d1 |  d2 |  d3 |  d4 |  r1 |  r2 |  r3 |  r4 |
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
           Destination 2           Router 2
   +-----+-----+-----+-----+-----+-----+-----+-----+---
   |  d1 |  d2 |  d3 |  d4 |  r1 |  r2 |  r3 |  r4 | ...
   +-----+-----+-----+-----+-----+-----+-----+-----+---

6. Link Layer Parameters per Interface

   This section lists the options that affect the operation of the data
   link layer on a per-interface basis.

6.1. Trailer Encapsulation Option

   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.

   The code for this option is 34, and its length is 1.

    Code   Len  Value
   +-----+-----+-----+
   |  34 |  1  | 0/1 |
   +-----+-----+-----+

6.2. ARP Cache Timeout Option

   This option specifies the timeout in seconds for ARP cache entries.
   The time is specified as a 32-bit unsigned integer.

   The code for this option is 35, and its length is 4.

    Code   Len           Time
   +-----+-----+-----+-----+-----+-----+
   |  35 |  4  |  t1 |  t2 |  t3 |  t4 |
   +-----+-----+-----+-----+-----+-----+

6.3. Ethernet Encapsulation Option

   This option specifies whether or not the client should use Ethernet
   Version 2 (RFC 894 [15]) or IEEE 802.3 (RFC 1042 [16]) 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.




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RFC 2132        DHCP Options and BOOTP Vendor Extensions      March 1997


   The code for this option is 36, and its length is 1.

    Code   Len  Value
   +-----+-----+-----+
   |  36 |  1  | 0/1 |
   +-----+-----+-----+

7. TCP Parameters

   This section lists the options that affect the operation of the TCP
   layer on a per-interface basis.

7.1. TCP Default TTL Option

   This option specifies the default TTL that the client should use when
   sending TCP segments.  The value is represented as an 8-bit unsigned
   integer.  The minimum value is 1.

   The code for this option is 37, and its length is 1.

    Code   Len   TTL
   +-----+-----+-----+
   |  37 |  1  |  n  |
   +-----+-----+-----+

7.2. TCP Keepalive Interval Option

   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.

   The code for this option is 38, and its length is 4.

    Code   Len           Time
   +-----+-----+-----+-----+-----+-----+
   |  38 |  4  |  t1 |  t2 |  t3 |  t4 |
   +-----+-----+-----+-----+-----+-----+

7.3. TCP Keepalive Garbage Option

   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 0 indicates that a garbage octet
   should not be sent. A value of 1 indicates that a garbage octet
   should be sent.




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   The code for this option is 39, and its length is 1.

    Code   Len  Value
   +-----+-----+-----+
   |  39 |  1  | 0/1 |
   +-----+-----+-----+

8. Application and Service Parameters

   This section details some miscellaneous options used to configure
   miscellaneous applications and services.

8.1. Network Information Service Domain Option

   This option specifies the name of the client's NIS [17] domain.  The
   domain is formatted as a character string consisting of characters
   from the NVT ASCII character set.

   The code for this option is 40.  Its minimum length is 1.

    Code   Len      NIS Domain Name
   +-----+-----+-----+-----+-----+-----+---
   |  40 |  n  |  n1 |  n2 |  n3 |  n4 | ...
   +-----+-----+-----+-----+-----+-----+---

8.2. Network Information Servers Option

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

   The code for this option is 41.  Its minimum length is 4, and the
   length MUST be a multiple of 4.

    Code   Len         Address 1               Address 2
   +-----+-----+-----+-----+-----+-----+-----+-----+--
   |  41 |  n  |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 |  ...
   +-----+-----+-----+-----+-----+-----+-----+-----+--

8.3. Network Time Protocol Servers Option

   This option specifies a list of IP addresses indicating NTP [18]
   servers available to the client.  Servers SHOULD be listed in order
   of preference.

   The code for this option is 42.  Its minimum length is 4, and the
   length MUST be a multiple of 4.




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    Code   Len         Address 1               Address 2
   +-----+-----+-----+-----+-----+-----+-----+-----+--
   |  42 |  n  |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 |  ...
   +-----+-----+-----+-----+-----+-----+-----+-----+--

8.4. Vendor Specific Information

   This option is used by clients and servers to exchange vendor-
   specific information.  The information is an opaque object of n
   octets, presumably interpreted by vendor-specific code on the clients
   and servers.  The definition of this information is vendor specific.
   The vendor is indicated in the vendor class identifier option.
   Servers not equipped to interpret the vendor-specific information
   sent by a client MUST ignore it (although it may be reported).
   Clients which do not receive desired vendor-specific information
   SHOULD make an attempt to operate without it, although they may do so
   (and announce they are doing so) in a degraded mode.

   If a vendor potentially encodes more than one item of information in
   this option, then the vendor SHOULD encode the option using
   "Encapsulated vendor-specific options" as described below:

   The Encapsulated vendor-specific options field SHOULD be encoded as a
   sequence of code/length/value fields of identical syntax to the DHCP
   options field with the following exceptions:

      1) There SHOULD NOT be a "magic cookie" field in the encapsulated
         vendor-specific extensions field.

      2) Codes other than 0 or 255 MAY be redefined by the vendor within
         the encapsulated vendor-specific extensions field, but SHOULD
         conform to the tag-length-value syntax defined in section 2.

      3) Code 255 (END), if present, signifies the end of the
         encapsulated vendor extensions, not the end of the vendor
         extensions field. If no code 255 is present, then the end of
         the enclosing vendor-specific information field is taken as the
         end of the encapsulated vendor-specific extensions field.

   The code for this option is 43 and its minimum length is 1.

   Code   Len   Vendor-specific information
   +-----+-----+-----+-----+---
   |  43 |  n  |  i1 |  i2 | ...
   +-----+-----+-----+-----+---






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   When encapsulated vendor-specific extensions are used, the
   information bytes 1-n have the following format:

    Code   Len   Data item        Code   Len   Data item       Code
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
   |  T1 |  n  |  d1 |  d2 | ... |  T2 |  n  |  D1 |  D2 | ... | ... |
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

8.5. NetBIOS over TCP/IP Name Server Option

   The NetBIOS name server (NBNS) option specifies a list of RFC
   1001/1002 [19] [20] NBNS name servers listed in order of preference.

   The code for this option is 44.  The minimum length of the option is
   4 octets, and the length must always be a multiple of 4.

    Code   Len           Address 1              Address 2
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+----
   |  44 |  n  |  a1 |  a2 |  a3 |  a4 |  b1 |  b2 |  b3 |  b4 | ...
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+----

8.6. NetBIOS over TCP/IP Datagram Distribution Server Option

   The NetBIOS datagram distribution server (NBDD) option specifies a
   list of RFC 1001/1002 NBDD servers listed in order of preference. The
   code for this option is 45.  The minimum length of the option is 4
   octets, and the length must always be a multiple of 4.

    Code   Len           Address 1              Address 2
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+----
   |  45 |  n  |  a1 |  a2 |  a3 |  a4 |  b1 |  b2 |  b3 |  b4 | ...
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+----

8.7. NetBIOS over TCP/IP Node Type Option

   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
   as follows:

      Value         Node Type
      -----         ---------
      0x1           B-node
      0x2           P-node
      0x4           M-node
      0x8           H-node





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   In the above chart, the notation '0x' indicates a number in base-16
   (hexadecimal).

   The code for this option is 46.  The length of this option is always
   1.

    Code   Len  Node Type
   +-----+-----+-----------+
   |  46 |  1  | see above |
   +-----+-----+-----------+

8.8. NetBIOS over TCP/IP Scope Option

   The NetBIOS scope option specifies the NetBIOS over TCP/IP scope
   parameter for the client as specified in RFC 1001/1002. See [19],
   [20], and [8] for character-set restrictions.

   The code for this option is 47.  The minimum length of this option is
   1.