netstat - show network status
netstat [-Aan] [-f address_family] [-M core] [-N system]
netstat [-bdgilmnqrSstu] [-f address_family] [-M core] [-N
system]
netstat [-bdn] [-I interface] [-M core] [-N system] [-w
wait]
netstat [-s] [-M core] [-N system] [-p protocol]
netstat [-a] [-f address_family] [-i | -I interface]
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 about the named
protocol.
The fifth form displays per interface statistics for the
specified address
family.
The options are as follows:
-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.
With the interface
display (options -I or -i), show multicast addresses.
-b With the interface display (options -I or -i), show
bytes in and
out, instead of packet statistics.
-d With either the interface display (options -I or -i)
or an interval
(option -w), 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:
Address Family Constant Description
inet AF_INET IP Version 4
inet6 AF_INET6 IP Version 6
ipx AF_IPX Novell IPX
atalk AF_APPLETALK AppleTalk
ns AF_NS Xerox NS Protocols
encap PF_KEY IPsec
local AF_LOCAL Local to Host
(i.e., pipes)
unix AF_UNIX Local to Host
(i.e., pipes)
-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.
-I interface
Show information about the specified interface; used
with a wait
interval as described below.
If the -a option is also present, multicast addresses currently
in use are shown for the given 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 -f address_family option (with the -s option)
is present,
show per-interface statistics on the given interface
for the
specified address_family.
-i Show the state of interfaces which have been autoconfigured (interfaces
statically configured into a system but not
located at
boot-time are not shown).
If the -a option 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 -f address_family option (with the -s option)
is present,
show per-interface statistics on all interfaces for
the specified
address_family.
-l With the -g option, display wider fields for the
IPv6 multicast
routing table "Origin" and "Group" columns.
-M core
Extract values associated with the name list from
the specified
core instead of the running kernel.
-m Show statistics recorded by the memory management
routines (the
network manages a private pool of memory buffers).
-N system
Extract the name list from the specified system instead of the
running kernel.
-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
Restrict the output to 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
program will
complain if protocol is unknown. If the -s option
is specified,
the per-protocol statistics are displayed. Otherwise the states
of the matching sockets are shown.
-q Only show interfaces that have seen packets (or
bytes if -b is
specified).
-r Show the routing tables. If the -s option is also
specified,
show routing statistics instead.
-S Make the -r command display the source selector part
of the
routes.
-s Show per-protocol statistics. If this option is repeated, counters
with a value of zero are suppressed.
-t With the -i option, display the current value of the
watchdog
timer function.
-u Limit statistics or address control block reports to
the AF_UNIX
address family.
-v Be verbose. Avoids truncation of long addresses.
-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 network but no specific host
address. When
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 a
single `*'. If a local port number is registered as being
in use for RPC
by portmap(8), its RPC service name or RPC service number
will be printed
in ``[]'' immediately after the port number.
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. If the destination is a network in numeric
format, the netmask (in /24 style format) is appended. 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 pkts (during updates).
C RTF_CLONING Generate new routes on use.
c RTF_CLONED Cloned routes (generated from
RTF_CLONING).
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
provides a
count of the number of packets sent using that route. The
MTU entry
shows the MTU associated with that route. This MTU value is
used as the
basis for the TCP maximum segment size (MSS). The `L' flag
appended to
the MTU value indicates that the value is locked, and that
path MTU discovery
is turned off for that route. A `-' indicates that
the MTU for
this route has not been set, and a default TCP maximum segment size will
be used. The interface 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 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.
nfsstat(1), ps(1), inet(3), netintro(4), route(4), hosts(5),
networks(5),
protocols(5), services(5), iostat(8), portmap(8), route(8),
tcpdrop(8),
trpt(8), vmstat(8)
The netstat command appeared in 4.2BSD. IPv6 support was
added by
WIDE/KAME project.
The notion of errors is ill-defined.
OpenBSD 3.6 April 18, 1994
[ Back ] |
