CompTIA Certifications

CompTIA Network+ 2009 Domain 5: Network Tools

Netstat Networking Utility

The netstat networking utility shows network statistics for the networking interfaces on the computer you are using. This command can be infinitely useful if you’re having a problem connecting to a certain resource – you will be able to see the current status of the connection and what port it is connecting on.

Here are the different options you can use with netstat:

H:\>netstat /?

Displays protocol statistics and current TCP/IP network connections.

NETSTAT [-a] [-b] [-e] [-n] [-o] [-p proto] [-r] [-s] [-v] [interval]

 -a            Displays all connections and listening ports.
 -b            Displays the executable involved in creating each connection or
 listening port. In some cases well-known executables host
 multiple independent components, and in these cases the
 sequence of components involved in creating the connection
 or listening port is displayed. In this case the executable
 name is in [] at the bottom, on top is the component it called,
 and so forth until TCP/IP was reached. Note that this option
 can be time-consuming and will fail unless you have sufficient
 -e            Displays Ethernet statistics. This may be combined with the -s
 -n            Displays addresses and port numbers in numerical form.
 -o            Displays the owning process ID associated with each connection.
 -p proto      Shows connections for the protocol specified by proto; proto
 may be any of: TCP, UDP, TCPv6, or UDPv6.  If used with the -s
 option to display per-protocol statistics, proto may be any of:
 IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, or UDPv6.
 -r            Displays the routing table.
 -s            Displays per-protocol statistics.  By default, statistics are
 shown for IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, and UDPv6;
 the -p option may be used to specify a subset of the default.
 -v            When used in conjunction with -b, will display sequence of
 components involved in creating the connection or listening
 port for all executables.
 interval      Redisplays selected statistics, pausing interval seconds
 between each display.  Press CTRL+C to stop redisplaying
 statistics.  If omitted, netstat will print the current
 configuration information once.

In the real world, you will often use netstat to see what network connections are open on the network interface. The output from netstat shows the connection, what port you are connected to (e.g. 1434 or http), and the status of the connection.