netstat [-Aan] [-f address_family] [-M core] [-N system]
     netstat [-dghimnrs] [-f address_family] [-M core] [-N system]
     netstat [-dn] [-I interface] [-M core] [-N system] [-w wait]
     netstat [-p protocol] [-M core] [-N system]

DESCRIPTION

     The netstat command symbolically displays the contents of various net-
     work-related data structures.  There are a number of output formats, de-
     pending on the options for the information presented.  The first form of
     the command displays a list of active sockets for each protocol.  The
     second form presents the contents of one of the other network data struc-
     tures according to the option selected.  Using the third form, with a
     wait interval specified, netstat will continuously display the informa-
     tion regarding packet traffic on the configured network interfaces.  The
     fourth form displays statistics about the named protocol.

     The options have the following meaning:

     -A    With the default display, show the address of any protocol control
           blocks associated with sockets; used for debugging.

     -a    With the default display, show the state of all sockets; normally
           sockets used by server processes are not shown.

     -d    With either interface display (option -i or an interval, as de-
           scribed below), show the number of dropped packets.

     -f address_family
           Limit statistics or address control block reports to those of the
           specified address family. The following address families are recog-
           nized: inet, for AF_INET, ipx, for AF_IPX, ns, for AF_NS, iso, for
           AF_ISO, local, for AF_LOCAL, and unix, for AF_UNIX.

     -g    Show information related to multicast (group address) routing.  By
           default, show the IP Multicast virtual-interface and routing ta-
           bles.  If the -s option is also present, show multicast routing
           statistics.

     -h    Show the state of the IMP host table (obsolete).

     -I interface
           Show information about the specified interface; used with a wait
           interval as described below.

     -i    Show the state of interfaces which have been auto-configured (in-
           terfaces statically configured into a system, but not located at
           boot time are not shown).  If the -a options is also present, mul-
           ticast addresses currently in use are shown for each Ethernet in-
           terface and for each IP interface address.  Multicast addresses are
           shown on separate lines following the interface address with which
           they are associated.


     -p protocol
           Show statistics about protocol, which is either a well-known name
           for a protocol or an alias for it.  Some protocol names and aliases
           are listed in the file /etc/protocols. A null response typically
           means that there are no interesting numbers to report.  The program
           will complain if protocol is unknown or if there is no statistics
           routine for it.

     -s    Show per-protocol statistics.  If this option is repeated, counters
           with a value of zero are suppressed.

     -r    Show the routing tables.  When -s is also present, show routing
           statistics instead.

     -w wait
           Show network interface statistics at intervals of wait seconds.

     The default display, for active sockets, shows the local and remote ad-
     dresses, send and receive queue sizes (in bytes), protocol, and the in-
     ternal state of the protocol.  Address formats are of the form
     ``host.port'' or ``network.port'' if a socket's address specifies a net-
     work but no specific host address.  When known the host and network ad-
     dresses are displayed symbolically according to the data bases /etc/hosts
     and /etc/networks, respectively.  If a symbolic name for an address is
     unknown, or if the -n option is specified, the address is printed numeri-
     cally, according to the address family.  For more information regarding
     the Internet ``dot format,'' refer to inet(3)).  Unspecified, or ``wild-
     card'', addresses and ports appear as ``*''.  If a local port number is
     registered as being in use for RPC by portmap(8) it's RPC service name or
     RPC service number will be printed in [ ] immediately after the port num-
     ber.

     The interface display provides a table of cumulative statistics regarding
     packets transferred, errors, and collisions.  The network addresses of
     the interface and the maximum transmission unit (``mtu'') are also dis-
     played.

     The routing table display indicates the available routes and their sta-
     tus.  Each route consists of a destination host or network and a gateway
     to use in forwarding packets.  The flags field shows a collection of in-
     formation about the route stored as binary choices.  The individual flags
     are discussed in more detail in the route(8) and route(4) manual pages.
     The mapping between letters and flags is:

     1       RTF_PROTO2       Protocol specific routing flag #1
     2       RTF_PROTO1       Protocol specific routing flag #2
     B       RTF_BLACKHOLE    Just discard pkts (during updates)
     C       RTF_CLONING      Generate new routes on use
     D       RTF_DYNAMIC      Created dynamically (by redirect)
     G       RTF_GATEWAY      Destination requires forwarding by intermediary
     H       RTF_HOST         Host entry (net otherwise)
     shows the mtu associated with that route.  This mtu value is used as the
     basis for the TCP maximum segment size.  A `-' indicates that the mtu for
     this route has not been set, and a default TCP maximum segment size will
     be used.  The interface entry indicates the network interface utilized
     for the route.

     When netstat is invoked with the -w option and a wait interval argument,
     it displays a running count of statistics related to network interfaces.
     An obsolescent version of this option used a numeric parameter with no
     option, and is currently supported for backward compatibility.  This dis-
     play consists of a column for the primary interface (the first interface
     found during autoconfiguration) and a column summarizing information for
     all interfaces.  The primary interface may be replaced with another in-
     terface with the -I option.  The first line of each screen of information
     contains a summary since the system was last rebooted.  Subsequent lines
     of output show values accumulated over the preceding interval.

SEE ALSO

     nfsstat(1),  ps(1),  hosts(5),  networks(5),  protocols(5),  services(5),
      trpt(8),  trsp(8),  iostat(8),  vmstat(8)

HISTORY

     The netstat command appeared in 4.2BSD.

BUGS

     The notion of errors is ill-defined.

4.2 Berkeley Distribution       April 18, 1994                               3