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NETSTAT(1) General Commands Manual NETSTAT(1) NAME netstat -- show network status and statistics SYNOPSIS netstat [-j jail] [--libxo] [-46AaCLnPRSTWx] [-f protocol_family | -p protocol] netstat -i | -I interface [-j jail] [--libxo] [-46abdhnW] [-f address_family] [-M core] [-N system] netstat -w wait [-j jail] [--libxo] [-I interface] [-46d] [-M core] [-N system] [-q howmany] netstat -s [-j jail] [--libxo] [-46sz] [-f protocol_family | -p protocol] [-M core] [-N system] netstat -i | -I interface -s [-j jail] [--libxo] [-46s] [-f protocol_family | -p protocol] [-M core] [-N system] netstat -m [-j jail] [--libxo] [-M core] [-N system] netstat -B [-j jail] [--libxo] [-z] [-I interface] netstat -r [-j jail] [--libxo] [-46nW] [-F fibnum] [-f address_family] netstat -rs [-j jail] [--libxo] [-s] [-M core] [-N system] netstat -g [-j jail] [--libxo] [-46W] [-f address_family] netstat -gs [-j jail] [--libxo] [-46s] [-f address_family] [-M core] [-N system] netstat -Q [-j jail] [--libxo] netstat -o -4 | -6 netstat -O -4 | -6 DESCRIPTION The netstat command shows the contents of various network-related data structures. The arguments passed determine which of the below output formats the command uses. netstat [-46AaCLnRSTWx] [-f protocol_family | -p protocol] [-j jail] Display a list of active sockets (protocol control blocks) for each network protocol. The default display for active sockets shows the local and re- mote addresses, send and receive queue sizes (in bytes), proto- col, and the internal state of the protocol. Address formats are of the form "host.port" or "network.port" if a socket's ad- dress specifies a network but no specific host address. When known, the host and network addresses are displayed symboli- cally according to the databases hosts(5) and networks(5), re- spectively. If a symbolic name for an address is unknown, or if the -n option is specified, the address is printed numeri- cally, according to the address family. For more information regarding the Internet IPv4 "dot format", refer to inet(3). Unspecified, or "wildcard", addresses and ports appear as "*". --libxo Generate output via libxo(3) in a selection of differ- ent human and machine readable formats. See xo_options(7) for details on command line arguments. -4 Show IPv4 only. See "GENERAL OPTIONS". -6 Show IPv6 only. See "GENERAL OPTIONS". -A Show the address of a protocol control block (PCB) as- sociated with a socket; used for debugging. -a Show the state of all sockets; normally sockets used by server processes are not shown. -c Show the used TCP stack for each session. -C Show the congestion control algorithm and diagnostic information of TCP sockets. -L Show the size of the various listen queues. The first count shows the number of unaccepted connections, the second count shows the amount of unaccepted incomplete connections, and the third count is the maximum number of queued connections. -n Do not resolve numeric addresses and port numbers to names. See "GENERAL OPTIONS". -P Display the log ID for each socket. -R Display the flowid and flowtype for each socket. flowid is a 32 bit hardware specific identifier for each flow. flowtype defines which protocol fields are hashed to produce the id. A complete listing is avail- able in sys/mbuf.h under M_HASHTYPE_*. -S Show network addresses as numbers (as with -n) but show ports symbolically. -T Display diagnostic information from the TCP control block. Fields include the number of packets requiring retransmission, received out-of-order, and those adver- tising a zero-sized window. -W Avoid truncating addresses even if this causes some fields to overflow. -x Display socket buffer and TCP timer statistics for each internet socket. The -x flag causes netstat to output all the informa- tion recorded about data stored in the socket buffers. The fields are: R-HIWA Receive buffer high water mark, in bytes. S-HIWA Send buffer high water mark, in bytes. R-LOWA Receive buffer low water mark, in bytes. S-LOWA Send buffer low water mark, in bytes. R-BCNT Receive buffer byte count. S-BCNT Send buffer byte count. R-BMAX Maximum bytes that can be used in the receive buffer. S-BMAX Maximum bytes that can be used in the send buffer. rexmt Time, in seconds, to fire Retransmit Timer, or 0 if not armed. persist Time, in seconds, to fire Retransmit Persistence, or 0 if not armed. keep Time, in seconds, to fire Keep Alive, or 0 if not armed. 2msl Time, in seconds, to fire 2*msl TIME_WAIT Timer, or 0 if not armed. delack Time, in seconds, to fire Delayed ACK Timer, or 0 if not armed. rcvtime Time, in seconds, since last packet received. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -p protocol Filter by protocol. See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -i | -I interface [-46abdhnW] [-f address_family] [-M core] [-N system] [-j jail] Show the state of all network interfaces or a single interface which have been auto-configured (interfaces statically config- ured into a system, but not located at boot time are not shown). An asterisk ("*") after an interface name indicates that the interface is "down". When netstat is invoked with -i (all interfaces) or -I interface, it provides a table of cumulative statistics regard- ing packets transferred, errors, and collisions. The network addresses of the interface and the maximum transmission unit ("mtu") are also displayed. If both -i and -I are specified, -I overrides any instances of -i. -4 Show IPv4 only. See "GENERAL OPTIONS". -6 Show IPv6 only. See "GENERAL OPTIONS". -a Multicast addresses currently in use are shown for each Ethernet interface and for each IP interface address. Multicast addresses are shown on separate lines follow- ing the interface address with which they are associ- ated. -b Show the number of bytes in and out. -d Show the number of dropped output packets. -h Print all counters in human readable form. -n Do not resolve numeric addresses and port numbers to names. See "GENERAL OPTIONS". -W Avoid truncating addresses even if this causes some fields to overflow. See "GENERAL OPTIONS". However, in most cases field widths are determined automatically with the -i option, and this option has little effect. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -w wait [-I interface] [-46d] [-M core] [-N system] [-q howmany] [-j jail] At intervals of wait seconds, display the information regarding packet traffic on all configured network interfaces or a single interface. 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. By default, this display summa- rizes information for all interfaces. Information for a spe- cific interface may be displayed with the -I interface option. -I interface Only show information regarding interface -4 Show IPv4 only. See "GENERAL OPTIONS". -6 Show IPv6 only. See "GENERAL OPTIONS". -d Show the number of dropped output packets. -M Use an alternative core. See "GENERAL OPTIONS". -N Use an alternative kernel image. See "GENERAL OPTIONS". -q Exit after howmany outputs. -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -o -4 | -6 Print nexthop (nhops) information associated with routing en- tries. When used with -4 or -6, limit the output to IPv4 or IPv6 routes respectively. This option provides details about individual nexthop addresses used in routing decisions. netstat -O -4 | -6 Print nexthop groups (nhgrp) information associated with rout- ing entries. When used with -4 or -6, restrict the output to IPv4 or IPv6 nexthop groups respectively. This option shows grouped nexthop entries for multipath or load-balanced routing setups. netstat -s [-46sz] [-f protocol_family | -p protocol] [-M core] [-N system] [-j jail] Display system-wide statistics for each network protocol. -4 Show IPv4 only. See "GENERAL OPTIONS". -6 Show IPv6 only. See "GENERAL OPTIONS". -s If -s is repeated, counters with a value of zero are suppressed. -z Reset statistic counters after displaying them. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -p protocol Filter by protocol. See "GENERAL OPTIONS". -M Use an alternative core. See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -i | -I interface -s [-46s] [-f protocol_family | -p protocol] [-M core] [-N system] [-j jail] Display per-interface statistics for each network protocol. If both -i and -I are specified, -I overrides any instances of -i. -4 Show IPv4 only See "GENERAL OPTIONS". -6 Show IPv6 only See "GENERAL OPTIONS". -s If -s is repeated, counters with a value of zero are suppressed. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -p protocol Filter by protocol. See "GENERAL OPTIONS". -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -m [-M core] [-N system] [-j jail] Show statistics recorded by the memory management routines (mbuf(9)). The network manages a private pool of memory buffers. -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -B [-z] [-I interface] [-j jail] Show statistics about bpf(4) peers. This includes information like how many packets have been matched, dropped and received by the bpf device, also information about current buffer sizes and device states. The bpf(4) flags displayed when netstat is invoked with the -B option represent the underlying parameters of the bpf peer. Each flag is represented as a single lower case letter. The mapping between the letters and flags in order of appearance are: p Set if listening promiscuously i BIOCIMMEDIATE has been set on the device f BIOCGHDRCMPLT status: source link addresses are being filled automatically s BIOCGSEESENT status: see packets originating locally and remotely on the interface. a Packet reception generates a signal l BIOCLOCK status: descriptor has been locked For more information about these flags, please refer to bpf(4). -z Reset statistic counters after displaying them. -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -r [-46AnW] [-F fibnum] [-f address_family] [-M core] [-N system] [-j jail] Display the contents of routing tables. When netstat is invoked with the routing table option -r, it lists the available routes and their status. Each route con- sists of a destination host or network, and a gateway to use in forwarding packets. The flags field shows a collection of in- formation about the route stored as binary choices. The indi- vidual 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 The route represents a broadcast address 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 ad- dress of the outgoing interface. The refcnt field gives the current number of active uses of the route. Connection ori- ented protocols normally hold on to a single route for the du- ration 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. -4 Show IPv4 only. See "GENERAL OPTIONS". -6 Show IPv6 only. See "GENERAL OPTIONS". -n Do not resolve numeric addresses and port numbers to names. See "GENERAL OPTIONS". -W Show the path MTU for each route, and print interface names with a wider field size. -F Display the routing table with the number fibnum. If the specified fibnum is -1 or -F is not specified, the default routing table is displayed. -f Display the routing table for a particular address_family. -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -rs [-s] [-M core] [-N system] [-j jail] Display routing statistics. -s If -s is repeated, counters with a value of zero are suppressed. -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -g [-46W] [-f address_family] [-M core] [-N system] [-j jail] Display the contents of the multicast virtual interface tables, and multicast forwarding caches. Entries in these tables will appear only when the kernel is actively forwarding multicast sessions. This option is applicable only to the inet and inet6 address families. -4 Show IPv4 only See "GENERAL OPTIONS". -6 Show IPv6 only See "GENERAL OPTIONS". -W Avoid truncating addresses even if this causes some fields to overflow. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -gs [-46s] [-f address_family] [-M core] [-N system] [-j jail] Show multicast routing statistics. -4 Show IPv4 only See "GENERAL OPTIONS". -6 Show IPv6 only See "GENERAL OPTIONS". -s If -s is repeated, counters with a value of zero are suppressed. -f protocol_family Filter by protocol_family. See "GENERAL OPTIONS". -M Use an alternative core See "GENERAL OPTIONS". -N Use an alternative kernel image See "GENERAL OPTIONS". -j jail Run inside a jail. See "GENERAL OPTIONS". netstat -Q [-j jail] Show netisr(9) statistics. The flags field shows available ISR handlers: C NETISR_SNP_FLAGS_M2CPUID Able to map mbuf to cpu id D NETISR_SNP_FLAGS_DRAINEDCPU Has queue drain handler F NETISR_SNP_FLAGS_M2FLOW Able to map mbuf to flow id -j jail Run inside a jail. See "GENERAL OPTIONS". GENERAL OPTIONS Some options have the general meaning: -4 Is shorthand for -f inet (Show only IPv4) -6 Is shorthand for -f inet6 (Show only IPv6) -f address_family, -p protocol Limit display to those records of the specified address_family or a single protocol. The following address families and protocols are recognized: Family Protocols inet (AF_INET) divert, icmp, igmp, ip, ipsec, pim, sctp, tcp, udp inet6 (AF_INET6) icmp6, ip6, ipsec6, rip6, sctp, tcp, udp pfkey (PF_KEY) pfkey netgraph, ng (AF_NETGRAPH) ctrl, data unix (AF_UNIX) link (AF_LINK) The program will complain if protocol is unknown or if there is no statistics routine for it. -M Extract values associated with the name list from the specified core instead of the default /dev/kmem. -N Extract the name list from the specified system instead of the default, which is the kernel image the system has booted from. -n Show network addresses and ports as numbers. Normally netstat attempts to resolve addresses and ports, and display them symbol- ically. Specifying -n twice will also disable printing the key- word "default" for the default IPv4 and IPv6 routes when display- ing contents of routing tables. -W Wider output; expand address fields, etc, to avoid truncation. Non-numeric values such as domain names may still be truncated; use the -n option if necessary to avoid ambiguity. -j jail Perform the actions inside the jail. This allows network state to be accessed even if the netstat binary is not available in the jail. EXAMPLES Show packet traffic information (packets, bytes, errors, packet drops, etc) for interface re0 updated every 2 seconds and exit after 5 out- puts: netstat -w 2 -q 5 -I re0 Show statistics for ICMP on any interface: netstat -s -p icmp Show routing tables: netstat -r Same as above, but without resolving numeric addresses and port numbers to names: netstat -rn Show IPv4 listening sockets: netstat -4l SEE ALSO fstat(1), nfsstat(1), procstat(1), ps(1), sockstat(1), libxo(3), xo_options(7), bpf(4), inet(4), route(4), unix(4), hosts(5), networks(5), protocols(5), services(5), iostat(8), route(8), vmstat(8), mbuf(9) HISTORY The netstat command appeared in 4.2BSD. IPv6 support was added by WIDE/KAME project. BUGS The notion of errors is ill-defined. FreeBSD 15.0 July 16, 2025 NETSTAT(1)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY | BUGS
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