vlan11.htm

所见过的最好的VLAN学习资料

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<body lang=ZH-CN link=blue vlink=purple style='tab-interval:21.0pt;text-justify-trim:
punctuation'>

<div class=Section1 style='layout-grid:15.6pt'>

<p class=MsoNormal align=center style='text-align:center'><b style='mso-bidi-font-weight:
normal'><span style='font-size:14.0pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>传统型路由器存在的意义</span></b><b
style='mso-bidi-font-weight:normal'><span lang=EN-US style='font-size:14.0pt'><o:p></o:p></span></b></p>

<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
style='font-size:12.0pt;font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman";color:red'>路由器的必要性</span></b><b
style='mso-bidi-font-weight:normal'><span lang=EN-US style='font-size:12.0pt;
color:red'><o:p></o:p></span></b></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>三层交换机的价格，在问世之<span class=GramE>初非常</span>昂贵，但是现在<span
style='color:blue'>它们的价格已经下降了许多</span>。目前国外一些廉价机型的售价，折合成人民币后仅为一万多元，而且还在继续下降中。</span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman";color:red'>既然三层交换机能够提供比传统型路由器更为高速的路由处理，那么网络中还有使用路由器的必要吗</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>？</span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>答案是：“<span style='color:blue'>是</span>”。</span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
lang=EN-US><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>使用路由器的必要性，主要表现在以下几个方面：</span></p>

<p class=MsoNormal align=left style='margin-left:21.0pt;text-align:left;
text-indent:-21.0pt;mso-pagination:widow-orphan;mso-list:l3 level1 lfo11;
tab-stops:list 21.0pt'><![if !supportLists]><span lang=EN-US style='font-family:
Wingdings;mso-fareast-font-family:Wingdings;mso-bidi-font-family:Wingdings;
color:blue'><span style='mso-list:Ignore'>l<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>用于与</span><span
lang=EN-US style='color:blue'>WAN</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>连接</span><span
lang=EN-US style='color:blue'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>三层交换机终究是“交换机”。也就是说，绝大多数机型<span style='color:red'>只配有</span></span><span
lang=EN-US style='color:red'>LAN</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:red'>（以太网）接口</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>。在少数高端交换机上也有用于连接</span><span lang=EN-US>WAN</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>的串行接口或是</span><span lang=EN-US>ATM</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>接口，但在大多数情况下，连接</span><span lang=EN-US>WAN</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>还是需要用到路由器。</span></p>

<p class=MsoNormal align=left style='margin-left:21.0pt;text-align:left;
text-indent:-21.0pt;mso-pagination:widow-orphan;mso-list:l3 level1 lfo11;
tab-stops:list 21.0pt'><![if !supportLists]><span lang=EN-US style='font-family:
Wingdings;mso-fareast-font-family:Wingdings;mso-bidi-font-family:Wingdings;
color:blue'><span style='mso-list:Ignore'>l<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>保证网络安全</span><span
lang=EN-US style='color:blue'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>在三层交换机上，通过数据包过滤也能确保一定程度的网络安全。但是使用路由器所提供的各种网络安全功能，用户可以构建更为安全可靠的网络。</span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>路由器提供的网络安全功能中，除了最基本的数据包过滤功能外，还能基于</span><span class=SpellE><span
lang=EN-US>IPSec</span></span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>构建</span><span
lang=EN-US>VPN</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>（</span><span lang=EN-US>Virtual
Private Network</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>）、利用</span><span lang=EN-US>RADIUS</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>进行用户认证等等。</span></p>

<p class=MsoNormal align=left style='margin-left:21.0pt;text-align:left;
text-indent:-21.0pt;mso-pagination:widow-orphan;mso-list:l3 level1 lfo11;
tab-stops:list 21.0pt'><![if !supportLists]><span lang=EN-US style='font-family:
Wingdings;mso-fareast-font-family:Wingdings;mso-bidi-font-family:Wingdings;
color:blue'><span style='mso-list:Ignore'>l<span style='font:7.0pt "Times New Roman"'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span></span><![endif]><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>支持除</span><span
lang=EN-US style='color:blue'>TCP/IP</span><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman";
color:blue'>以外的网络架构</span><span lang=EN-US style='color:blue'><o:p></o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>尽管</span><span lang=EN-US>TCP/IP</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>已经成为当前网络协议架构的主流，但还有不少网络利用</span><span lang=EN-US>Novell
Netware</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>下的</span><span lang=EN-US>IPX/SPX</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>或</span><span lang=EN-US>Macintosh</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>下的</span><span class=SpellE><span lang=EN-US>Appletalk</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>等网络协议。三层交换机中，除了部分高端机型外基本上还只支持</span><span lang=EN-US>TCP/IP</span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>。因此，<span style='color:blue'>在需要使用除</span></span><span
lang=EN-US style='color:blue'>TCP/IP</span><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman";
color:blue'>之外其他网络协议的环境下，路由器还是必不可少的</span><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>。</span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
lang=EN-US><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal align=left style='text-align:left;mso-pagination:widow-orphan'><span
style='font-size:9.0pt;font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman";color:red'>注：在少数高端交换机上，也能支持上述路由器的功能。例如</span><span
lang=EN-US style='font-size:9.0pt;color:red'>Cisco</span><span