netstat



NETSTAT(1)                 OpenBSD Reference Manual                 NETSTAT(1)


NAME

     netstat - show network status


SYNOPSIS

     netstat [-AaBn] [-f address_family] [-p protocol] [-M core] [-N system]
     netstat [-bdFgilmnqrstu] [-f address_family] [-p protocol] [-M core]
             [-N system] [-T tableid]
     netstat [-bdhn] [-c count] [-I interface] [-M core] [-N system] [-w wait]
     netstat [-v] [-M core] [-N system] -P pcbaddr
     netstat [-s] [-M core] [-N system] [-p protocol]
     netstat [-a] [-f address_family] [-p protocol] [-i | -I interface]
     netstat [-W interface]


DESCRIPTION

     The netstat command symbolically displays the contents of various
     network-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 structures according to the option selected.  Using the
     third form, with a wait interval specified, netstat will continuously
     display the information regarding packet traffic on the configured
     network interfaces.  The fourth form displays internals of the protocol
     control block (PCB) and the socket structure.  The fifth form displays
     statistics about the named protocol.  The sixth form displays per
     interface statistics for the specified address family.  The final form
     displays per interface statistics for the specified wireless (802.11)
     device.

     The options are as follows:

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

     -a      With the default display, show the state of all sockets; normally
             sockets used by server processes are not shown.  With the
             interface display (options -I or -i), show multicast addresses.

     -B      With the default display, show buffer sizes for TCP sockets.
             This includes the send window size, receive window size and
             congestion window size.

     -b      With the interface display (options -I or -i), show bytes in and
             out, instead of packet statistics.

     -c count
             Display count updates, then exit.  This option has no effect
             unless -w is specified as well.

     -d      With either the interface display (options -I or -i) or an
             interval (option -w), show the number of dropped packets.

     -F      When showing routes, only show routes whose gateway are in the
             same address family as the destination.

     -f address_family
             Limit statistics or address control block reports to those of the
             specified address_family.

             The following address families are recognized:

                   Address Family    Constant      Description
                   encap             PF_KEY        IPsec
                   inet              AF_INET       IP Version 4
                   inet6             AF_INET6      IP Version 6
                   local             AF_LOCAL      Local to Host (i.e., pipes)
                   mpls              AF_MPLS       MPLS
                   pflow             PF_FLOW       pflow data export
                   unix              AF_UNIX       Local to Host (i.e., pipes)

     -h      Use unit suffixes to reduce the number of digits shown with the
             -b and -w options.

     -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.

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

             If the -a option is also present, multicast addresses currently
             in use are shown for the given interface and for each IP
             interface address.  Multicast addresses are shown on separate
             lines following the interface address with which they are
             associated.

             If the -f address_family option (with the -s option) is present,
             show per-interface statistics on the given interface for the
             specified address_family.

     -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 option is also present, multicast 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.

             If the -f address_family option (with the -s option) is present,
             show per-interface statistics on all interfaces for the specified
             address_family.

     -l      With the -g option, display wider fields for the IPv6 multicast
             routing table "Origin" and "Group" columns.

     -M core
             Extract values associated with the name list from the specified
             core instead of the running kernel.

     -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
             running kernel.

     -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 pcbaddr
             Display the contents of the socket or protocol control block
             (PCB) located at the kernel virtual address pcbaddr.  PCB
             addresses can be obtained using the -A flag.  When used with the
             -v option, also print socket, domain and protocol specific
             structures.

     -p protocol
             Restrict the output to 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.  The program will
             complain if protocol is unknown.  If the -s option is specified,
             the per-protocol statistics are displayed.  Otherwise the states
             of the matching sockets are shown.

     -q      Only show interfaces that have seen packets (or bytes if -b is
             specified).

     -r      Show the routing tables.  If the -s option is also specified,
             show routing statistics instead.  When used with the -v option,
             also print routing labels.

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

     -T tableid
             Select an alternate routing table to query.  The default is to
             use the current routing table.

     -t      With the -i option, display the current value of the watchdog
             timer function.

     -u      Limit statistics or address control block reports to the AF_UNIX
             address family.

     -v      Show extra (verbose) detail for the routing tables (-r), or avoid
             truncation of long addresses.  When used with the -P option, also
             print socket, domain and protocol specific structures.

     -W interface
             (IEEE 802.11 devices only) Show per-interface IEEE 802.11
             wireless statistics.

     -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 network but no specific host address.  When
     known, the host and network addresses are displayed symbolically
     according to the databases /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 information regarding the Internet ``dot format'', refer to
     inet(3).  Unspecified or ``wildcard'' addresses and ports appear as a
     single `*'.  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 displayed.

     The routing table display indicates the available routes and their
     status.  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
     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_PROTO1       Protocol specific routing flag #1.
     2    RTF_PROTO2       Protocol specific routing flag #2.
     3    RTF_PROTO3       Protocol specific routing flag #3.
     B    RTF_BLACKHOLE    Just discard pkts (during updates).
     C    RTF_CLONING      Generate new routes on use.
     c    RTF_CLONED       Cloned routes (generated from RTF_CLONING).
     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).
     P    RTF_MPATH        Multipath route.
     R    RTF_REJECT       Host or net unreachable.
     S    RTF_STATIC       Manually added.
     T    RTF_MPLS         MPLS route.
     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
     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).  The `L' flag
     appended to the MTU value indicates that the value is locked, and that
     path MTU discovery is turned off for that route.  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
     display 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 information contains a summary since the system was last rebooted.
     Subsequent lines of output show values accumulated over the preceding
     interval.


SEE ALSO

     fstat(1), nfsstat(1), ps(1), systat(1), tcpbench(1), top(1), inet(3),
     netintro(4), route(4), hosts(5), networks(5), protocols(5), services(5),
     iostat(8), portmap(8), pstat(8), route(8), tcpdrop(8), trpt(8), vmstat(8)


HISTORY

     The netstat command appeared in 4.2BSD.  IPv6 support was added by the
     WIDE/KAME project.


BUGS

     The notion of errors is ill-defined.

OpenBSD 5.4                     August 22, 2012                    OpenBSD 5.4

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