|NETSTAT(1)||General Commands Manual||NETSTAT(1)|
netstat — show
netstat command shows various aspects
of network status. The default display shows information about all active
network connections and sockets.
The first form of the command displays a list of active sockets
for each protocol. The second form displays per-interface statistics for the
specified wireless (802.11) device. The third form displays statistics
related to memory use. The fourth form displays per-interface statistics.
The fifth form continuously displays the information regarding packet
traffic on the configured network interfaces. The sixth form displays
per-protocol statistics. The seventh form shows information related to
multicast routing. The eighth form displays information about routing
domains. The ninth form displays information about routing tables. The final
form displays internals of the protocol control block (PCB) and the socket
structure. The forms are shown in order of precedence: for example, if
-rg is specified, then
ignored in favour of
The options are as follows:
-Pflag. When used with the
-rflag it shows the internal addresses of the routing table. Only the super-user can see these addresses; unprivileged users will see them as 0x0.
-i), show bytes in and out, instead of packet statistics.
-wis specified as well.
-i) or an interval (option
-w), show only the number of dropped packets.
-i) or an interval (option
-w), show only the number of errors on the interface.
The following address families are recognized:
||IP Version 4|
||IP Version 6|
||Alias for unix|
||Local to Host (i.e., pipes)|
-soption is also present, show multicast routing statistics.
-goption, display wider fields for the IPv6 multicast routing table "Origin" and "Group" columns.
netstatinterprets addresses and attempts to display them symbolically). This option may be used with any of the display formats.
-Aflag. When used with the
-voption, also print socket, domain and protocol specific structures. Only the super-user can use the
-P option requires the ability to
open /dev/kmem which may be restricted based
upon the value of the kern.allowkmem
-soption is specified, the per-protocol statistics are displayed. Otherwise the states of the matching sockets are shown.
-soption is also specified, show routing statistics instead. When used with the
-voption, also print routing labels.
-ioption, display the current value of the watchdog timer function.
-r), or avoid truncation of long addresses. When used with the
-Poption, also print socket, domain and protocol specific structures.
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 addresses are displayed
symbolically according to the hosts(5)
database. 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_ntop(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).|
|b||RTF_BROADCAST||Correspond to a local broadcast address.|
|C||RTF_CLONING||Generate new routes on use.|
|c||RTF_CLONED||Cloned routes (generated from RTF_CLONING).|
|D||RTF_DYNAMIC||Created dynamically (by redirect).|
|d||RTF_DONE||Completed (for routing messages only).|
|G||RTF_GATEWAY||Destination requires forwarding by intermediary.|
|H||RTF_HOST||Host entry (net otherwise).|
|h||RTF_CACHED||Referenced by gateway route.|
|L||RTF_LLINFO||Valid protocol to link address translation.|
|l||RTF_LOCAL||Correspond to a local address.|
|M||RTF_MODIFIED||Modified dynamically (by redirect).|
|m||RTF_MULTICAST||Correspond to a multicast address.|
|R||RTF_REJECT||Host or net unreachable.|
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.
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
-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
fstat(1), nfsstat(1), ps(1), systat(1), tcpbench(1), top(1), inet_ntop(3), netintro(4), route(4), hosts(5), protocols(5), services(5), iostat(8), portmap(8), pstat(8), route(8), tcpdrop(8), trpt(8), vmstat(8)
netstat command appeared in
4.2BSD. IPv6 support was added by the WIDE/KAME
The notion of errors is ill-defined.
|July 18, 2020||OpenBSD-current|