NETSTAT(1) General Commands Manual NETSTAT(1)
netstat - show network status
netstat [ -Aan ] [ -f address_family ] [ system ] [ core ]
netstat [ -himnrs ] [ -f address_family ] [ system ] [ core ]
netstat [ -n ] [ -I interface ] interval [ system ] [ core ]
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
structures according to the option selected. Using the third form,
with an interval specified, netstat will continuously display the
information regarding packet traffic on the configured network inter‐
The options have the following meaning:
-A With the default display, show the address of any protocol con‐
trol blocks associated with sockets; used for debugging.
-a With the default display, show the state of all sockets; nor‐
mally sockets used by server processes are not shown.
-h Show the state of the IMP host table.
-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).
Show information only about this interface; used with an inter‐
val as described below.
-m Show statistics recorded by the memory management routines (the
network manages a private pool of memory buffers).
-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.
-s Show per-protocol statistics.
-r Show the routing tables. When -s is also present, show routing
Limit statistics or address control block reports to those of
the specified address family. The following address families
are recognized: inet, for AF_INET, ns, for AF_NS, and unix, for
The arguments, system and core allow substitutes for the defaults
``/vmunix'' and ``/dev/kmem''.
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 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 infor‐
mation regarding the Internet ``dot format,'' refer to inet(3N).
Unspecified, or ``wildcard'', addresses and ports appear as ``*''.
The interface display provides a table of cumulative statistics regard‐
ing packets transferred, errors, and collisions. The network addresses
of the interface and the maximum transmission unit (``mtu'') are also
The routing table display indicates the available routes and their sta‐
tus. Each route consists of a destination host or network and a gate‐
way to use in forwarding packets. The flags field shows the state of
the route (``U'' if ``up''), whether the route is to a gateway (``G''),
and whether the route was created dynamically by a redirect (``D'').
Direct routes are created for each interface attached to the local
host; the gateway field for such entries shows the address of the out‐
going 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 pro‐
tocols 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
When netstat is invoked with an interval argument, it displays a run‐
ning count of statistics related to network interfaces. This display
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 infor‐
mation contains a summary since the system was last rebooted. Subse‐
quent lines of output show values accumulated over the preceding inter‐
iostat(1), vmstat(1), hosts(5), networks(5), protocols(5), services(5),
The notion of errors is ill-defined. Collisions mean something else
for the IMP.
4.2 Berkeley Distribution May 8, 1986 NETSTAT(1)