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

NAME
     netstat — show network status

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.

     netstat [-AaLnSWx] [-f protocol_family | -p protocol] [-M core]
	     [-N system]
	     Display a list of active sockets (protocol control blocks) for
	     each network protocol, for a particular protocol_family, or for a
	     single protocol.  If -A is also present, show the address of a
	     protocol control block (PCB) associated with a socket; used for
	     debugging.	 If -a is also present, show the state of all sockets;
	     normally sockets used by server processes are not shown.  If -L
	     is also present, show the size of the various listen queues.  The
	     first count shows the number of unaccepted connections, the sec‐
	     ond count shows the amount of unaccepted incomplete connections,
	     and the third count is the maximum number of queued connections.
	     If -S is also present, show network addresses as numbers (as with
	     -n) but show ports symbolically.  If -x is present display full
	     socket buffer statistics for each internet socket.

     netstat -i | -I interface [-abdhntW] [-f address_family] [-M core]
	     [-N system]
	     Show the state of all network interfaces or a single interface
	     which have been auto-configured (interfaces statically configured
	     into a system, but not located at boot time are not shown).  An
	     asterisk (“*”) after an interface name indicates that the inter‐
	     face is “down”.  If -a is also present, multicast addresses cur‐
	     rently 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 associ‐
	     ated.  If -b is also present, show the number of bytes in and
	     out.  If -d is also present, show the number of dropped packets.
	     If -h is also present, print all counters in human readable form.
	     If -t is also present, show the contents of watchdog timers.  If
	     -W is also present, print interface names using a wider field
	     size.

     netstat -w wait [-I interface] [-d] [-M core] [-N system] [-q howmany]
	     At intervals of wait seconds, display the information regarding
	     packet traffic on all configured network interfaces or a single
	     interface.	 If -q is also present, exit after howmany outputs.
	     If -d is also present, show the number of dropped packets.

     netstat -s [-s] [-z] [-f protocol_family | -p protocol] [-M core]
	     [-N system]
	     Display system-wide statistics for each network protocol, for a
	     particular protocol_family, or for a single protocol.  If -s is
	     repeated, counters with a value of zero are suppressed.  If -z is
	     also present, reset statistic counters after displaying them.

     netstat -i | -I interface -s [-f protocol_family | -p protocol] [-M core]
	     [-N system]
	     Display per-interface statistics for each network protocol, for a
	     particular protocol_family, or for a single protocol.

     netstat -m [-M core] [-N system]
	     Show statistics recorded by the memory management routines
	     (mbuf(9)).	 The network manages a private pool of memory buffers.

     netstat -B [-z] [-I interface]
	     Show statistics about bpf(4) peers.  This includes information
	     like how many packets have been matched, dropped and received by
	     the bpf device, also information about current buffer sizes and
	     device states.

     netstat -r [-AanW] [-f address_family] [-M core] [-N system]
	     Display the contents of all routing tables, or a routing table
	     for a particular address_family.  If -A is also present, show the
	     contents of the internal Patricia tree structures; used for
	     debugging.	 If -a is also present, show protocol-cloned routes
	     (routes generated by an RTF_PRCLONING parent route); normally
	     these routes are not shown.  When -W is also present, show the
	     path MTU for each route, and print interface names with a wider
	     field size.

     netstat -rs [-s] [-M core] [-N system]
	     Display routing statistics.  If -s is repeated, counters with a
	     value of zero are suppressed.

     netstat -g [-W] [-f address_family] [-M core] [-N system]
	     Display the contents of the multicast virtual interface tables,
	     and multicast forwarding caches.  Entries in these tables will
	     appear only when the kernel is actively forwarding multicast ses‐
	     sions.  This option is applicable only to the inet and inet6
	     address families.

     netstat -gs [-s] [-f address_family] [-M core] [-N system]
	     Show multicast routing statistics.	 If -s is repeated, counters
	     with a value of zero are suppressed.

     Some options have the general meaning:

     -f address_family, -p protocol
	   Limit display to those records of the specified address_family or a
	   single protocol.  The following address families and protocols are
	   recognized:

	   Family		       Protocols
	   inet (AF_INET)	       divert, icmp, igmp, ip, ipsec, pim,
				       sctp, tcp, udp
	   inet6 (AF_INET6)	       icmp6, ip6, ipsec6, rip6, tcp, udp
	   pfkey (PF_KEY)	       pfkey
	   atalk (AF_APPLETALK)	       ddp
	   netgraph, ng (AF_NETGRAPH)  ctrl, data
	   ipx (AF_IPX)		       ipx, spx
	   unix (AF_UNIX)
	   link (AF_LINK)

	   The program will complain if protocol is unknown or if there is no
	   statistics routine for it.

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

     -N	   Extract the name list from the specified system instead of the
	   default, which is the kernel image the system has booted from.

     -n	   Show network addresses and ports as numbers.	 Normally netstat
	   attempts to resolve addresses and ports, and display them symboli‐
	   cally.

     -W	   In certain displays, avoid truncating addresses even if this causes
	   some fields to overflow.

     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 hosts(5) and
     networks(5), 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 IPv4 “dot format”, refer to inet(3).  Unspecified, 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_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)
     b	  RTF_BROADCAST	   The route represents a broadcast address
     C	  RTF_CLONING	   Generate new routes on use
     c	  RTF_PRCLONING	   Protocol-specified 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
     W	  RTF_WASCLONED	   Route was generated as a result of cloning
     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.  By
     default, this display summarizes information for all interfaces.  Infor‐
     mation for a specific interface may be displayed with the -I option.

     The bpf(4) flags displayed when netstat is invoked with the -B option
     represent the underlying parameters of the bpf peer.  Each flag is repre‐
     sented as a single lower case letter.  The mapping between the letters
     and flags in order of appearance are:

     p	  Set if listening promiscuously
     i	  BIOCIMMEDIATE has been set on the device
     f	  BIOCGHDRCMPLT status: source link addresses are being filled auto‐
	  matically
     s	  BIOCGSEESENT status: see packets originating locally and remotely on
	  the interface.
     a	  Packet reception generates a signal
     l	  BIOCLOCK status: descriptor has been locked

     For more information about these flags, please refer to bpf(4).

     The -x flag causes netstat to output all the information recorded about
     data stored in the socket buffers.	 The fields are:

     R-MBUF    Number of mbufs in the receive queue.
     S-MBUF    Number of mbufs in the send queue.
     R-CLUS    Number of clusters, of any type, in the receive queue.
     S-CLUS    Number of clusters, of any type, in the send queue.
     R-HIWA    Receive buffer high water mark, in bytes.
     S-HIWA    Send buffer high water mark, in bytes.
     R-LOWA    Receive buffer low water mark, in bytes.
     S-LOWA    Send buffer low water mark, in bytes.
     R-BCNT    Receive buffer byte count.
     S-BCNT    Send buffer byte count.
     R-BMAX    Maximum bytes that can be used in the receive buffer.
     S-BMAX    Maximum bytes that can be used in the send buffer.

SEE ALSO
     fstat(1), nfsstat(1), procstat(1), ps(1), sockstat(1), bpf(4), inet(4),
     route(4), unix(4), hosts(5), networks(5), protocols(5), services(5),
     iostat(8), route(8), trpt(8), vmstat(8), mbuf(9)

HISTORY
     The netstat command appeared in 4.2BSD.

     IPv6 support was added by WIDE/KAME project.

BUGS
     The notion of errors is ill-defined.

BSD			       January 10, 2010				   BSD
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