.\"	$OpenBSD: netstat.1,v 1.3 1996/07/08 22:09:42 ccappuc Exp $
.\"	$NetBSD: netstat.1,v 1.11 1995/10/03 21:42:43 thorpej Exp $
.\"
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.\"	from: @(#)netstat.1	8.8 (Berkeley) 4/18/94
.\"
.Dd April 18, 1994
.Dt NETSTAT 1
.Os BSD 4.2
.Sh NAME
.Nm netstat
.Nd show network status
.Sh SYNOPSIS
.Nm netstat
.Op Fl Aan
.Op Fl f Ar address_family
.Op Fl M Ar core
.Op Fl N Ar system
.Nm netstat
.Op Fl dghimnrs
.Op Fl f Ar address_family
.Op Fl M Ar core
.Op Fl N Ar system
.Nm netstat
.Op Fl dn
.Op Fl I Ar interface
.Op Fl M Ar core
.Op Fl N Ar system
.Op Fl w Ar wait
.Nm netstat
.Op Fl p Ar protocol
.Op Fl M Ar core
.Op Fl N Ar system
.Sh DESCRIPTION
The
.Nm 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
.Ar wait
interval specified,
.Nm netstat
will continuously display the information regarding packet
traffic on the configured network interfaces.
The fourth form displays statistics about the named protocol.
.Pp
The options have the following meaning:
.Bl -tag -width flag
.It Fl A
With the default display,
show the address of any protocol control blocks associated with sockets; used
for debugging.
.It Fl a
With the default display,
show the state of all sockets; normally sockets used by
server processes are not shown.
.It Fl d
With either interface display (option
.Fl i
or an interval, as described below),
show the number of dropped packets.
.It Fl f Ar address_family 
Limit statistics or address control block reports to those
of the specified
.Ar address family  .
The following address families
are recognized:
.Ar inet  ,
for
.Dv AF_INET  ,
.Ar ns ,
for
.Dv AF_NS  ,
.Ar iso ,
for
.Dv AF_ISO ,
and
.Ar unix  ,
for
.Dv AF_UNIX  .
.It Fl g
Show information related to multicast (group address) routing.
By default, show the IP Multicast virtual-interface and routing tables.
If the
.Fl s
option is also present, show multicast routing statistics.
.It Fl h
Show the state of the
.Tn IMP
host table (obsolete).
.It Fl I Ar interface 
Show information about the specified interface;
used with a
.Ar wait
interval as described below.
.It Fl 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
.Fl a
options 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.
.It Fl M
Extract values associated with the name list from the specified core
instead of the default
.Pa /dev/kmem .
.It Fl m
Show statistics recorded by the memory management routines
(the network manages a private pool of memory buffers).
.It Fl N
Extract the name list from the specified system instead of the default
.Pa /bsd .
.It Fl n
Show network addresses as numbers (normally
.Nm netstat
interprets addresses and attempts to display them
symbolically).
This option may be used with any of the display formats.
.It Fl p Ar protocol 
Show statistics about
.Ar 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
.Pa /etc/protocols .
A null response typically means that there are no interesting numbers to
report.
The program will complain if
.Ar protocol
is unknown or if there is no statistics routine for it.
.It Fl s
Show per-protocol statistics.
If this option is repeated, counters with a value of zero are suppressed.
.It Fl r
Show the routing tables.
When
.Fl s
is also present, show routing statistics instead.
.It Fl w Ar wait
Show network interface statistics at intervals of
.Ar wait
seconds.
.El
.Pp
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
.Pa /etc/hosts
and
.Pa /etc/networks ,
respectively.  If a symbolic name for an address is unknown, or if
the
.Fl n
option is specified, the address is printed numerically, according
to the address family.
For more information regarding
the Internet ``dot format,''
refer to
.Xr inet 3 ) .
Unspecified,
or ``wildcard'', addresses and ports appear as ``*''.
.Pp
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.
.Pp
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
a collection of information about the route stored as
binary choices.  The individual flags are discussed in more
detail in the
.Xr route 8
and
.Xr route 4
manual pages.
The mapping between letters and flags is:
.Bl -column XXXX RTF_BLACKHOLE
1	RTF_PROTO2	Protocol specific routing flag #1 
2	RTF_PROTO1	Protocol specific routing flag #2 
B	RTF_BLACKHOLE	Just discard pkts (during updates) 
C	RTF_CLONING	Generate new routes on use 
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
.El
.Pp
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.  A
.Sq -
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.
.Pp
When
.Nm netstat
is invoked with the
.Fl w
option and a
.Ar 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
.Fl 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.
.Sh SEE ALSO
.Xr nfsstat 1 ,
.Xr ps 1 ,
.Xr hosts 5 ,
.Xr networks 5 ,
.Xr protocols 5 ,
.Xr services 5 ,
.Xr trpt 8 ,
.Xr trsp 8 ,
.Xr iostat 8 ,
.Xr vmstat 8
.Sh HISTORY
The
.Nm netstat
command appeared in
.Bx 4.2 .
.\" .Sh FILES
.\" .Bl -tag -width /dev/kmem -compact
.\" .It Pa /bsd
.\" default kernel namelist
.\" .It Pa /dev/kmem
.\" default memory file
.\" .El
.Sh BUGS
The notion of errors is ill-defined.