急??急?！！这题怎么理解？？

蓝色飞鱼

<P><IMG src="http://www.spoto.net/bbs/images/Emotions/68.gif"></P><P>［此帖子已被 蓝色飞鱼 在 2005-8-19 13:13:28 编辑过］</P><p>［此帖子已被 蓝色飞鱼 在 2005-8-19 13:21:10 编辑过］

sky-worm

<P>恩恩,楼上解释的没错呀!!!!</P><P>LZ如果还是不懂,可以看看书,在&lt;学习指南&gt;P188-192有解释ICMP的过程,里面就有讲到了</P><P>P192还有几个例子,做完,应该就会懂了!!!</P>

蓝色飞鱼

<P>Host TestKingA needs to communications with the e-mail server shown in the<BR>exhibt.<BR>What address will be placed on the destination address field of the frame when it<BR>leaves host TestKingA?<BR>A. The MAC address of TestKingA<BR>B. The MAC address of switch TestKing1<BR>C. The MAC address of the E0 interface of the TestKing3 router.<BR>D. The MAC address of the E1 interface of the TestKing3 router.<BR>E. The MAC address of switch TestKing2<BR>F. The MAC address of the email server<BR>Answer: C</P><P>为什么是C</P><p>［此帖子已被 蓝色飞鱼 在 2005-8-19 13:22:48 编辑过］

single

<P>PC 发包，到SERVER，一路，源IP地址和目的IP地址是不变的。而源MAC地址和目的MAC地址是一直在变的，包每经过一台路由器，源就变成这个网关的MAC地址，目的就为下一跳网关的MAC地址。</P>