NETSTAT(1)NETSTAT(1)NAMEnetstat - show network status
SYNOPSISnetstat [ -Aan ] [ -f address_family ] [ system ] [ core ]
netstat [ -himnrs ] [ -f address_family ] [ system ] [ core ]
netstat [ -n ] [ -I interface ] interval [ system ] [ core ]
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 an interval specified, netstat will continuously display the
information regarding packet traffic on the configured network
interfaces.
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.
-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).
-I interface
Show information only about this interface; used with an
interval 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
statistics instead.
-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, ns, for AF_NS, and unix, for
AF_UNIX.
The arguments, system and core allow substitutes for the defaults
``/mach'' 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
information 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
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 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
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 an interval argument, it displays a
running 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 information contains a summary since the system was last
rebooted. Subsequent lines of output show values accumulated over the
preceding interval.
SEE ALSOiostat(1), vm_stat(1), hosts(5), networks(5), protocols(5), services(5)BUGS
The notion of errors is ill-defined. Collisions mean something else
for the IMP.
4.2 Berkeley Distribution May 8, 1986 NETSTAT(1)
