NETSTAT(1) BSD General Commands Manual NETSTAT(1)NAMEnetstat — show network status
SYNOPSISnetstat [-Aan] [-f address_family] [-M core] [-N system]
netstat [-bdghiLlmnqrSsTtv] [-f address_family] [-M core] [-N system]
netstat [-dn] [-I interface] [-M core] [-N system] [-w wait]
netstat [-M core] [-N system] [-p protocol]
netstat [-M core] [-N system] [-p protocol] -P pcbaddr
netstat [-i] [-I Interface] [-p protocol]
netstat [-is] [-f address_family] [-I Interface]
netstat [-s] [-I Interface] -B
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 fifth and
sixth forms display per interface statistics for the specified protocol
or address family.
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.
-B With the default display, show the current bpf(4) peers. To show
only the peers listening to a specific interface, use the -I
option. If the -s option is present, show the current bpf(4) sta‐
tistics.
-b With the interface display (option -i), show bytes in and out,
instead of packets in and out.
-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; inet6, for AF_INET6; arp, for AF_ARP;
ns, for AF_NS; iso, for AF_ISO; atalk, for AF_APPLETALK; mpls, for
AF_MPLS; and local or unix, for AF_LOCAL.
-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 -f address_family option (with
the -s option) or the -p protocol option is present, show per-
interface statistics on the interface for the specified
address_family or protocol, respectively.
-h When used with -b in combination with either -i or -I, output
"human-readable" byte counts.
-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. If the -f address_family option (with
the -s option) or the -p protocol option is present, show per-
interface statistics on all interfaces for the specified
address_family or protocol, respectively.
-L Don't show link-level routes (e.g., IPv4 ARP or IPv6 neighbour
cache).
-l With the -g option, display wider fields for the IPv6 multicast
routing table "Origin" and "Group" columns.
-M Extract values associated with the name list from the specified
core instead of the default /dev/kmem.
-m Show statistics recorded by the mbuf 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 /netbsd.
-n Show network addresses and ports as numbers (normally netstat
interprets addresses and ports and attempts to display them symbol‐
ically). This option may be used with any of the display formats.
-P pcbaddr
Dump the contents of the protocol control block (PCB) located at
kernel virtual address pcbaddr. This address may be obtained using
the -A flag. The default protocol is TCP, but may be overridden
using the -p flag.
-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.
-q Show software interrupt queue setting/statistics for all protocols.
-r Show the routing tables. When -s is also present, show routing
statistics instead.
-S Show network addresses as numbers (as with -n, but show ports sym‐
bolically).
-s Show per-protocol statistics. If this option is repeated, counters
with a value of zero are suppressed.
-T Show MPLS Tags for the routing tables. If multiple tags exists,
they will be comma separated, first tag being the BoS one.
-t With the -i option, display the current value of the watchdog timer
function.
-v Show extra (verbose) detail for the routing tables (-r), or avoid
truncation of long addresses.
-w wait
Show network interface statistics at intervals of wait seconds.
-X Force use of sysctl(3) when retrieving information. Some features
of netstat may not be (fully) supported when using sysctl(3). This
flag forces the use of the latter regardless, and emits a message
if a not yet fully supported feature is used in conjunction with
it. This flag might be removed at any time; do not rely on its
presence.
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 ``*''. You can use
the fstat(1) command to find out which process or processes hold refer‐
ences to a socket.
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_PROTO1 Protocol specific routing flag #1
2 RTF_PROTO2 Protocol specific routing flag #2
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)
p RTF_ANNOUNCE Link level proxy
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 mtu
entry shows the mtu associated with that route. This mtu value is used
as the basis for the TCP maximum segment size. The 'L' flag appended to
the mtu value indicates that the value is locked, and that path mtu dis‐
covery 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 used 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.
The first character of the flags column in the -B option shows the status
of the bpf(4) descriptor which has three different values: Idle ('I'),
Waiting ('W') and Timed Out ('T'). The second character indicates
whether the promisc flag is set. The third character indicates the sta‐
tus of the immediate mode. The fourth character indicates whether the
peer will have the ability to see the packets sent. And the fifth char‐
acter shows the header complete flag status.
SEE ALSOfstat(1), nfsstat(1), ps(1), sockstat(1), vmstat(1), inet(3), bpf(4),
hosts(5), networks(5), protocols(5), services(5), iostat(8), trpt(8)HISTORY
The netstat command appeared in 4.2BSD. IPv6 support was added by
WIDE/KAME project.
BUGS
The notion of errors is ill-defined.
BSD October 20, 2012 BSD
