SunSolve Internal

Infodoc ID		Synopsis		Date
12987		What are all the 2.4 ndd variables?		1 Mar 1996

Description

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Most TCP, IP, UDP and ARP tuning in Solaris is done via the ndd
command. You can list all of the appropriate variables by supplying
ndd with the driver name and a ?, i.e.:

  % ndd /dev/arp \?
  % ndd /dev/ip \?
  % ndd /dev/tcp \?
  % ndd /dev/udp \?

Note: Under Solaris 2.5 or higher, you will need to be root to display
these variables.

You can change ndd variables by supplying the -set option, the
variable name, and the value, i.e.:

  % ndd -set /dev/ip ip_forwarding 0

If you wish a ndd variables to get set upon every boot, you should put
a line for it in the file /etc/rc2.d/S69inet:

  % cat /etc/rc2.d/S69inet
  ...
  #
  # Set configurable parameters.
  #
  ndd -set /dev/tcp tcp_old_urp_interpretation 1

Many variables have two options: 1 (True) and 0 (False).

Note: in all of the following examples, the default values for 2.4 are
listed. Other OSs may differ, and can always be discovered by
typing:

   # ndd device variable

I.e.:

  # ndd /dev/ip ip_debug
  0

One word of warning concerning the ndd variables: They should be
considered quite volatile, and might totally change from one release
of Solaris to another. Only the variables that are the most useful, or
the least likely to change, are listed below, but even these could be
potentially modified in new releases of the OS. Unlisted variables,
which can be viewed with the ndd command, should be considered even
less static.

IP Variables
------------

ip_def_ttl

  Determines the default Time To Live value for standard IP packets.
  The default value is 255.

ip_forwarding

  Determines if the workstation will route packets. This variable can be
  one of three selections:
  
    0     Never forward
    1     Always forward
    2     Only forward when two or more interfaces are up

  The default value is 2.

ip_send_redirects

  Determines whether the host should send ICMP redirects when it routes
  packets. The default value is 1 (True).

TCP Variables
-------------

tcp_close_wait_interval

  Despite the misleading name, this variable actually sets the time
  wait interval (the 2MSL value). The default value is 240000 ms (4
  minutes).

tcp_ip_ttl
  
  Determines the default Time To Live for TCP/IP packets. The default
  value is 255.

tcp_keepalive_interval

  Determines how frequently to test if an idle connection is still
  alive. The default value is 7200000 ms (2 hours).

tcp_mss_def

  Determines the Maximum Segment Size for nonlocal packets (i.e.,
  packets to be sent to different networks or subnets). The default
  value is 536 bytes.

tcp_recv_hiwat

  Determines the maximum value of the TCP receive window. The default
  value is 8192 (8k).

tcp_smallest_anon_port

  Determines the smallest TCP port number that may be used for an
  anonymous connection. The default value is 32768.

tcp_xmit_hiwat

  Determines the maximum value of the TCP transmit window. The default
  value is 8192 (8k).

tcp_xmit_lowat

  Determines the minimum value of the TCP transmit window. The default
  value is 2048 (2k).

UDP Variables
-------------

udp_def_ttl    

  Determines the default Time To Live for UDP packets. The default
  value is 255.

udp_do_checksum

  Determines whether checksums should be done for UDP packets. The
  default value is 1 (True).

udp_recv_hiwat

  Determines the maximum value of the UDP receive window. The default
  value is 8192 (8k).

udp_smallest_anon_port

  Determines the smallest UDP port number that may be used for an
  anonymous connection. The default value is 32768.

udp_xmit_hiwat

  Determines the maximum value of the UDP transmit window. The default
  value is 8192 (8k).

udp_xmit_lowat

  Determines the minimum value of the UDP transmit window. The default
  value is 1024 (1k).

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