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RocketLink!--> Man page versions: OpenBSD FreeBSD NetBSD Others

NETSTAT(1)                 OpenBSD Reference Manual                 NETSTAT(1)

     netstat - show network status

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

     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 are as follows:

     -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, atalk, for AF_APPLETALK,
           ns, for AF_NS, iso, for AF_ISO, encap, for PF_KEY, 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

     -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.

     -M core
           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 system
           Extract the name list from the specified system instead of the de-
           fault /bsd.

     -n    Show network addresses as numbers (normally netstat interprets ad-
           dresses 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.

     -v    Be verbose. This currently has no effect.

     -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),  its RPC service name
     or RPC service number will be printed in ``[]'' immediately after the
     port number.

     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-

     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.  If the destination is a network in numeric
     format, the netmask (in /24 style format) is appended.  The flags field
     shows a collection of information about the route stored as binary choic-
     es.  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_PROTO1       Protocol specific routing flag #1.
     2       RTF_PROTO2       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 in-
     terface.  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 provides a
     count of the number of packets sent using that route.  The MTU entry
     shows the MTU associated with that route.  This MTU value is used as the
     basis for the TCP maximum segment size (MSS).  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.

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

     The netstat command appeared in 4.2BSD.

     The notion of errors is ill-defined.

OpenBSD 2.6                     April 18, 1994                               3

Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY
SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts
Institute of Technology, Free Software Foundation, FreeBSD Inc., and others.

(Corrections, notes, and links courtesy of RocketAware.com)

[Detailed Topics]
FreeBSD Sources for netstat(1)
OpenBSD sources for netstat(1)

[Overview Topics]

Up to: Communication Debugging - Status, tracing, and debugging communications and protocols.
Up to: Communication and Network Monitoring - status reporting, logging, et al

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