NETSTAT(1) BSD General Commands Manual NETSTAT(1)NAMEnetstat — show network status
SYNOPSISnetstat [-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]
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. 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
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 rec‐
ognized: inet, for AF_INET, ns, for AF_NS, iso, for AF_ISO, 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.
-h Show the state of the IMP host table (obsolete).
-I interface
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
(interfaces 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
interface 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
default /vmunix.
-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. 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
statistics instead.
-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 net‐
work but no specific host address. When known the host and network
addresses 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 numerically, according to the address family. For more informa‐
tion regarding the Internet ``dot format,'' refer to inet(3)). Unspeci‐
fied, 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_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
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. 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
interface with the -I option. The first line of each screen of informa‐
tion contains a summary since the system was last rebooted. Subsequent
lines of output show values accumulated over the preceding interval.
SEE ALSOiostat(1), nfsstat(1), ps(1), vmstat(1), hosts(5), networks(5),
protocols(5), services(5), trpt(8), trsp(8)HISTORY
The netstat command appeared in 4.2BSD.
BUGS
The notion of errors is ill-defined.
4.2 Berkeley Distribution April 18, 1994 4.2 Berkeley Distribution
