分类：教育/科学-外语学习
问题：急！谁能够帮忙解决一下这个网络翻译问题？Whatthreepro 
What three cesses does a router execute when it receives a packet from one network that is destined for another network? (Choose three.)  1.decapsulates the Layer 3 packet by stripping off the Layer 2 frame header  2.uses the destination MAC Address in the IP Header to What three cesses does a router execute when it receives a packet from one network that is destined for another network? (Choose three.)  1.decapsulates the Layer 3 packet by stripping off the Layer 2 frame header  2.uses the destination MAC Address in the IP Header to look up the next-hop address in the routing table  3.leaves the Layer 2 frame header intact when decapsulating the Layer 3 packet 4. uses the destination IP Address in the IP header to look up the next-hop address in the routing table  5.encapsulates the Layer 3 packet into the new Layer 2 frame and forwards it out the exit interface 6. encapsulates the Layer 3 packet into a special Layer 1 frame and forwards it to the exit interface 这是一道选择题，答案是1，4，5，请帮忙解释一下，越详细越好，（用翻译工具翻译的请免回答），想知道这道题的真正含义，先谢谢了
回答：（中文不是很顺溜，凑合看吧）
当路由器接收到一个要传送到另外一个网络的数据包时，它要执行哪几个操作（选择3个）：

1.去掉数据包的第二层报头，以获得第3层数据包
2.使用IP报头的目标物理地址从路由表获得下一站地址
3.当解码第3层数据包时，保持第二层报头
4.使用IP报头的目标IP地址从路由表获得下一站地址
5.将第3层数据包重新打包成第二层数据包，转发到输出接口
6.将第3层数据包重新打包成一个特殊的第1层数据包，转发到输出接口