User`s guide

a price. Therefore, do not be surprised if you get an error or two while installing these programs.

To help, we have provided a few troubleshooting tips to ease the pain.

Missing Files and/or Directory Errors

If you receive an error relating to a file or directory that is non-existent, the problem can be

solved by manually creating this directory or by creating a link to the necessary file. A Unix

“link” is similar to a Windows shortcut and will satisfy the installation script and any program

that needs the file.

1.Manually create the missing directory (for example, mkdir /usr/local/include/net).

2.Locate the missing file and copy it into the directory, or create a symbolic link to the file.

Missing libcrypto.0 File

This is one error that seems to be common; thus, we included specific instructions on how to

correct it. The problem is related to changes in where Linux places files as it is installed.

1.Create a symbolic link to the libcrypto.0 file using an existing libcrypto.0.x

file (for

example, ln libcrypto.0.x libcrypto.0).

2.Install RPM using the —nodep option.

3.2.4 Running Ethereal

Ethereal can be launched from the command line (ethereal&). Details about the program are

covered next.

3.2.4.1 Using Ethereal

Using Ethereal is basically the same regardless of the OS. The GUI and general operation of

this program is the same regardless of the platform on which it was installed, with the exception

of general file menu operations. Because of the similarities, we will cover the use of the program

once.

3.2.4.2 GUI Overview

After Ethereal is loaded, you will see three screens, as illustrated in Figure 9.1. Each of

these frames serves a unique purpose for the user, and will present the following information.

• Packet Summary—This is a list of all the captured packets, which includes the

packet number (1–65, 535), time-stamp, source and destination address, protocol,

and some brief information about the data in the packet.

• Packet Detail—This window contains more detailed information about the

packet, such as MAC addresses, IP address, packet header information, packet

size, packet type, and more. This is for those people interested in what type of

data a packet contains, but don’t care about the actual data. For example, if

you are troubleshooting a network, you can use this information to narrow

down possible problems.

• Packet Dump (Hex and ASCII)—This field contains the standard three columns

of information found in most sniffers. On the left is the memory value of the

packet; the middle contains the data in hex; and the right contains the ASCII