NETSTAT(1) BSD Reference Manual NETSTAT(1)
netstat - show network status
netstat [-Aan] [-f address_family] [-M core] [-N system]
netstat [-dghimnrs] [-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 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.
-d With either interface display (option -i or an interval, as de-
scribed below), show the number of dropped packets.
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, ns, for AF_NS, iso, for AF_ISO, and 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
-h Show the state of the IMP host table (obsolete).
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 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 de-
-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.
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
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 ``*''.
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. The flags field shows a collection of in-
formation 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_PROTO2 Protocol specific routing flag #1
2 RTF_PROTO1 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 interface en-
try 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.
iostat(1), nfsstat(1), ps(1), vmstat(1), hosts(5), networks(5),
protocols(5), services(5), trpt(8), trsp(8)
The netstat command appeared in 4.2BSD.
The notion of errors is ill-defined.
4.2 Berkeley Distribution April 18, 1994 3