tyt09fi.htm

tcpip 协议学习电子书籍 第一次上传东西

<CENTER><TABLE  BORDERCOLOR=#000040 BORDER=1 CELLSPACING=2 CELLPADDING=3 >

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P><I>Class</I>

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<P><I>Network Mask </I><I>Bytes</I>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P><I>Number of Hosts </I><I>per Network</I>

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<P><I>Valid Addresses</I>

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<P>A

<BR>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>1

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>16,777,216

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>1.0.0.1 to 126.255.255.254

<BR>

</FONT>

<TR>

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<P>B

<BR>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>2

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>65,534

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>128.0.0.1 to 191.255.255.254

<BR>

</FONT>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>C

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>3

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>254

<BR>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>224.0.0.0 to 255.255.255.254

<BR>

</FONT>

<TR>

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<P>D

<BR>

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<P>reserved

<BR>

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<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080><BR></FONT>

</TD>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080><BR></FONT>

</TD></TABLE></CENTER><P>The network mask is the IP address stripped of its network identifiers, leaving only the local machine address. For a Class A network, this strips one byte, whereas a Class B network strips two bytes (leaving two). The small Class C network strips three bytes as the network mask, leaving one byte to identify the local machine (hence the limit of 254 machines on the network). The sample network is configured as a Class B machine with the randomly chosen IP address network mask of 147.120 (not NIC-assigned).

<BR>

<P>The broadcast address identifies packets that are to be sent to all machines on the local network. Because a network card usually ignores any incoming packets that don't have its specific IP address in them, a special broadcast address can be set that the card can intercept in addition to locally destined messages. The broadcast address has the host portion (the local machine identifiers) set to either all 0s or all 1s, depending on the convention followed. For convenience, the broadcast address's network mask is usually the same as the local network mask.

<BR>

<P>Broadcast addresses might seem simple because there are only two possible settings. Such addresses, however, commonly cause problems because conflicting settings are used on a network. BSD UNIX used the convention of all 0s for releases 4.1 and 4.2, whereas 4.3BSD and SVR4 (System V Release 4) UNIX moved to all 1s for the broadcast address. The Internet standard specifies all 1s as the broadcast address. If problems are encountered on the network with broadcasts, check all the configurations to ensure they are using the same setting. The sample network uses an all 1s mask for its broadcast address.

<BR>

<P>The steps followed for configuring TCP/IP are straightforward, generally following the information required for each machine. The configuration steps are as follows:

<BR>

<UL>

<LI><B>Link drivers:</B> TCP/IP must be linked to the operating system's kernel or loaded during the boot stage to enable TCP/IP.

<BR></LI>

<BR>

<LI><B>Add host information:</B> Provide a list of all machines (hosts) on the network (used for name resolution).

<BR></LI>

<BR>

<LI><B>Establish routing tables:</B> Provide the information for routing packets properly if name resolution isn't sufficient.

<BR></LI>

<BR>

<LI><B>Set user access:</B> Configure the system to enable access in and out of the network, as well as establishing permissions.

<BR></LI>

<BR>

<LI><B>Remote device access:</B> Configure the system for access to remote printers, scanners, CD-ROM carousels, and other shared network devices.

<BR></LI>

<BR>

<LI><B>Configure the name domain server:</B> If using a distributed address lookup system such as Berkeley Internet Name Domain Server (BIND) or NIS, complete the name server files. (This step is necessary only if you are using BIND or a similar service.)

<BR></LI>

<BR>

<LI><B>Tune system for performance:</B> Because a system running TCP/IP has different behavior than one without TCP/IP, some system tuning is usually required.

<BR></LI>

<BR>

<LI><B>Configure NFS:</B> If the Network File System (NFS) is to be used, configure both the file system and the user access.

<BR></LI>

<BR>

<LI><B>Anonymous FTP:</B> If the system is to enable anonymous FTP access, configure the system and public directories for this service.

<BR></LI>

<BR>

</UL>

<P>You will use these steps (not necessarily in the sequence given) as the individual machines on the network are configured. The processes are different with each operating system, but the overall approach remains the same.

<BR>

<BR>

<A ID="E68E86" NAME="E68E86"></A>

<H3 ALIGN=CENTER>

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<FONT SIZE=5 COLOR="#FF0000"><B>UNIX TCP/IP Configuration</B></FONT></CENTER></H3>

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<P>Most UNIX TCP/IP operating systems rely on several files for configuration. These are summarized in Table 9.2. Remember that filenames can change with different implementations of the UNIX operating system, but the configuration information is consistent. I look at each of these files in more detail when I look at specific operating systems later today. These files apply only to UNIX usually; Windows NT, for example, uses a different set of tables.

<BR>

<BR>

<P ALIGN=CENTER>

<CENTER>

<FONT COLOR="#000080"><B>Table 9.2. TCP/IP UNIX configuration files.</B></FONT></CENTER>

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<P><B><I>File</I></B>

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<P><B><I>Description</I></B>

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<TR>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>/etc/hosts

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>Host names

<BR>

</FONT>

<TR>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>/etc/networks

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>Network names

<BR>

</FONT>

<TR>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>/etc/services

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>List of known services

<BR>

</FONT>

<TR>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>/etc/protocols

<BR>

</FONT>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>Supported protocols

<BR>

</FONT>

<TR>

<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>

<P>/etc/hosts.equiv

<BR>

</FONT>