NETSTAT(1) General Commands Manual NETSTAT(1)
NAME
netstat – show network status
SYNOPSIS
netstat [-AaLlnW] [-f address_family | -p protocol]
netstat [-gilns] [-v] [-f address_family] [-I interface]
netstat -i | -I interface [-w wait] [-c queue] [-abdgqRtS]
netstat -s [-s] [-f address_family | -p protocol] [-w wait]
netstat -i | -I interface -s [-f address_family | -p protocol]
netstat -m [-m]
netstat -r [-Aaln] [-f address_family]
netstat -rs [-s]
netstat -B [-I 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 statistics for the specified
protocol or address family. If a wait interval is specified, the protocol
information over the last interval seconds will be displayed. 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 and the flow hash; 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 Show statistics about bpf(4) devices. 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. The option -I show information only for the bpf
devices bound the specified interface.
-b With the interface display (option -i, as described below), show
the number of bytes in and out.
-c queue
With the queue statistics (option -q, as described below), show
only those for the specified queue.
-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, unix, for
AF_UNIX and vsock, for AF_VSOCK.
-g Show information related to multicast (group address) membership.
If the -s option is also present, show extended interface group
management statistics. If the -v option is specified, show link-
layer memberships; they are suppressed by default. Source lists
for each group will also be printed. Specifying -v twice will
print the control plane timers for each interface and the source
list counters for each group. If the -i is specified, only that
interface will be shown. If the -f is specified, only information
for the address family will be displayed.
-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 Show statistics recorded by the memory management routines (the
network stack manages a private pool of memory buffers). More
detailed information about the buffers, which includes their cache
related statistics, can be obtained by using -mm or -m -m option.
-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.
-q Show network interface send queue statistics. By default all
queues are displayed, unless specified with -c. This option
requires specifying an interface with -I option. More detailed
information about the queues, which includes their queueing
algorithm related statistics, can be obtained by using -qq or -q -q
option.
-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. More detailed information about the
route metrics are displayed with -ll for TCP round trip times -lll
for all metrics. Use the -z flags to display only entries with
non-zero RTT values. (“mtu”) are also displayed.
-R Show reachability information. Use with -i to show link-layer
reachability information for a given interface.
-s Show per-protocol statistics. If this option is repeated, counters
with a value of zero are suppressed. For security reasons, root
privileges are required to read TCP statistics and in the absence
of such privileges all TCP counters will be reported as zero.
-S Show interface link status and interface state information about
the specified interface. This option requires specifying an
interface with -I option.
-v Increase verbosity level.
-W In certain displays, avoid truncating addresses even if this causes
some fields to overflow.
-w wait
Show network interface or protocol statistics at intervals of wait
seconds.
-x Show extended link-layer reachability information in addition to
that shown by the -R flag.
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)
I RTF_IFSCOPE Route is associated with an interface scope
i RTF_IFREF Route is holding a reference to the interface
L RTF_LLINFO Valid protocol to link address translation
M RTF_MODIFIED Modified dynamically (by redirect)
m RTF_MULTICAST The route represents a multicast address
R RTF_REJECT Host or net unreachable
r RTF_ROUTER Host is a default router
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
Y RTF_PROXY Proxying; cloned routes will not be scoped
g RTF_GLOBAL Route to a destination of the global internet
(policy hint)
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.
A route which is marked with the RTF_IFSCOPE flag is instantiated for the
corresponding interface. A cloning route which is marked with the
RTF_PROXY flag will not generate new routes that are associated with its
interface scope.
When netstat is invoked with the -w option and a wait interval argument,
it displays a running count of statistics related to network interfaces
or protocols. 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
nfsstat(1), ps(1), inet(4), unix(4), hosts(5), networks(5), protocols(5),
route(8), services(5), iostat(8), bpf(4),
HISTORY
The netstat command appeared in 4.2BSD.
IPv6 support was added by WIDE/KAME project.
BUGS
The notion of errors is ill-defined.
Darwin June 15, 2001 Darwin