21-01-2013, 12:03 PM
Wireshark (Ethereal) Tutorial
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Running Wireshark
When you run the Wireshark program, the Wireshark graphical user interface shown in
Figure 2 will de displayed. Initially, no data will be displayed in the various windows.
The Wireshark interface has five major components:
The command menus are standard pulldown menus located at the top of the
window. Of interest to us now are the File and Capture menus. The File menu
allows you to save captured packet data or open a file containing previously
captured packet data, and exit the Wireshark application. The Capture menu
allows you to begin packet capture.
The packet-listing window displays a one-line summary for each packet
captured, including the packet number (assigned by Wireshark; this is not a
packet number contained in any protocol’s header), the time at which the packet
was captured, the packet’s source and destination addresses, the protocol type,
and protocol-specific information contained in the packet. The packet listing can
be sorted according to any of these categories by clicking on a column name. The
protocol type field lists the highest level protocol that sent or received this packet,
i.e., the protocol that is the source or ultimate sink for this packet.
The packet-header details window provides details about the packet selected
(highlighted) in the packet listing window. (To select a packet in the packet
listing window, place the cursor over the packet’s one-line summary in the packet
listing window and click with the left mouse button.). These details include
information about the Ethernet frame (assuming the packet was sent/receiverd
over an Ethernet interface) and IP datagram that contains this packet. The amount
of Ethernet and IP-layer detail displayed can be expanded or minimized by
clicking on the plus-or-minus boxes to the left of the Ethernet frame or IP
datagram line in the packet details window. If the packet has been carried over
TCP or UDP, TCP or UDP details will also be displayed, which can similarly be
expanded or minimized. Finally, details about the highest level protocol that sent
or received this packet are also provided.
The packet-contents window displays the entire contents of the captured frame,
in both ASCII and hexadecimal format.
Towards the top of the Wireshark graphical user interface, is the packet display
filter field, into which a protocol name or other information can be entered in
order to filter the information displayed in the packet-listing window (and hence
the packet-header and packet-contents windows). In the example below, we’ll
use the packet-display filter field to have Wireshark hide (not display) packets
except those that correspond to HTTP messages.
Taking Wireshark for a Test Run
The best way to learn about any new piece of software is to try it out! We’ll assume that
your computer is connected to the Internet via a wired Ethernet interface. Do the
following
1. Start up your favorite web browser, which will display your selected homepage.
2. Start up the Wireshark software. You will initially see a window similar to that
shown in Figure 2, except that no packet data will be displayed in the packetlisting,
packet-header, or packet-contents window, since Wireshark has not yet
begun capturing packets.
3. To begin packet capture, select the Capture pull down menu and select Options.
This will cause the “Wireshark: Capture Options” window to be displayed, as
shown in Figure 3.