NETSTAT(1)

NAME
netstat - show network status

SYNOPSIS
netstat [-AaLlnW] [-f address_family | -p protocol] [-M core] [-N system]
netstat [-gilns] [-f address_family] [-M core] [-N system]
netstat -i | -I interface [-w wait] [-abdgt] [-M core] [-N system]
netstat -s [-s] [-f address_family | -p protocol] [-M core] [-N system]
netstat -i | -I interface -s [-f address_family | -p protocol] [-M core] [-N system]
netstat -m [-M core] [-N system]
netstat -r [-Aaln] [-f address_family] [-M core] [-N system]
netstat -rs [-s] [-M core] [-N system]

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 statistics for the specified protocol or address family. The fifth form displays per-interface statistics for the specified protocol or address family. The sixth form displays mbuf(9) statistics. The seventh form displays routing table for the specified address family. The eighth form displays routing statistics.

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. With the routing table display (option -r, as described below), show protocol-cloned routes (routes generated by a RTF_PRCLONING parent route); normally these routes are not shown.

-b  With the interface display (option -i, as described below), show the number of bytes in and out.

-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 recognized: inet, for AF_INET, inet6, for AF_INET6 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.

-I interface
    Show information about the specified interface; used with a wait interval as described below. If the -s option is present, show per-interface protocol statistics on the interface for the specified address_family or protocol, or for all protocol families.

-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, 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 -s option is present, show per-interface statistics on all interfaces for the specified address_family or protocol, or for all protocol families.

-L  Show the size of the various listen queues. The first count shows the number of unaccepted connections. The second count shows the amount of unaccepted incomplete connections. The third count is the maximum number of queued connections.

-l  Print full IPv6 address.

-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 /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 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. The special protocol name “bdg” is used to show bridging statistics. 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.

-r  Show the routing tables. Use with -a to show protocol-cloned routes. When -s is also present, show routing statistics instead. When -l is also present, netstat assumes more columns are there and the maximum transmission unit (“mtu”) are also displayed.

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

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

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

OUTPUT
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. If 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 “*”.

Internet domain socket states:
CLOSED: The socket is not in use.

LISTEN: The socket is listening for incoming connections. Unconnected listening sockets like these are only displayed when using the -a option.

SYN_SENT: The socket is actively trying to establish a connection to a remote peer.

SYN_RCVD: The socket has passively received a connection request from a remote peer.

ESTABLISHED: The socket has an established connection between a local application and a remote peer.

CLOSE_WAIT: The socket connection has been closed by the remote peer, and the system is waiting for the local application to close its half of the connection.

LAST_ACK: The socket connection has been closed by the remote peer, the local application has closed its half of the connection, and the system is waiting for the remote peer to acknowledge the close.

FIN_WAIT_1: The socket connection has been closed by the local application, the remote peer has not yet acknowledged the close, and the system is waiting for it to close its half of the connection.

FIN_WAIT_2: The socket connection has been closed by the local application, the remote peer has acknowledged the close, and the system is waiting for it to close its half of the connection.

CLOSING: The socket connection has been closed by the local application and the remote peer simultaneously, and the remote peer has not yet acknowledged the close attempt of the local application.

TIME_WAIT: The socket connection has been closed by the local application, the remote peer has closed its half of the connection, and the system is waiting to be sure that the remote peer received the last acknowledgement.

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. 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 packets (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 provides a count of the number of packets sent using that route. 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 obsolete 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. Information for a specific interface may be displayed with the -I option.

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

HISTORY
The netstat command appeared in 4.2BSD.

IPv6 support was added by WIDE/KAME project.

FILES
/kernel
    default kernel namelist
/dev/kmem
    default memory file

BUGS
The notion of errors is ill-defined.