netstat man page on 4.4BSD

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NETSTAT(1)		  BSD General Commands Manual		    NETSTAT(1)

NAME
     netstat — show network status

SYNOPSIS
     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,
     depending 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
	   described 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 rec‐
	   ognized: inet, for AF_INET, ns, for AF_NS, iso, for AF_ISO, and
	   unix, for AF_UNIX.

     -g	   Show information related to multicast (group address) routing.  By
	   default, show the IP Multicast virtual-interface and routing
	   tables.  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
	   (interfaces 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
	   interface and for each IP interface address.	 Multicast addresses
	   are shown on separate lines following the interface address with
	   which they are associated.

     -M	   Extract values associated with the name list from the specified
	   core instead of the default /dev/kmem.

     -m	   Show statistics recorded by the memory management routines (the
	   network manages a private pool of memory buffers).

     -N	   Extract the name list from the specified system instead of the
	   default /vmunix.

     -n	   Show network addresses as numbers (normally netstat interprets
	   addresses and attempts to display them symbolically).  This option
	   may be used with any of the display formats.

     -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
     addresses, send and receive queue sizes (in bytes), protocol, and the
     internal 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
     addresses 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 numerically, according to the address family.  For more informa‐
     tion regarding the Internet ``dot format,'' refer to inet(3)).  Unspeci‐
     fied, or ``wildcard'', addresses and ports appear as ``*''.

     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
     information 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)
     L	     RTF_LLINFO	      Valid protocol to link address translation.
     M	     RTF_MODIFIED     Modified dynamically (by redirect)
     R	     RTF_REJECT	      Host or net unreachable
     S	     RTF_STATIC	      Manually added
     U	     RTF_UP	      Route usable
     X	     RTF_XRESOLVE     External daemon translates proto to link address

     Direct routes are created for each interface attached to the local host;
     the gateway field for such entries shows the address of the outgoing
     interface.	 The refcnt field gives the current number of active uses of
     the route.	 Connection oriented protocols normally hold on to a single
     route for the duration of a connection while connectionless protocols
     obtain a route while sending to the same destination.  The use field pro‐
     vides a count of the number of packets sent using that route.  The inter‐
     face 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
     interface with the -I option.  The first line of each screen of informa‐
     tion contains a summary since the system was last rebooted.  Subsequent
     lines of output show values accumulated over the preceding interval.

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

HISTORY
     The netstat command appeared in 4.2BSD.

BUGS
     The notion of errors is ill-defined.

4.2 Berkeley Distribution	April 18, 1994	     4.2 Berkeley Distribution
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