I had a wierd situation recently, could get the ip address, set up apt.conf and proxy correctly, but could not connect network, could ping a inner desttop, then my friend found that it responses twice when ping this ip, so it probably is that the ip is used by other people stactly, so I need to get a new automatic ip address, here is what I did,

netstat显示的连接状态有几种WAIT: FIN_WAIT_1,FIN_WAIT_2,CLOSE_WAIT和TIME_WAIT. 他们的含义要从TCP的连接中断过程说起

traceroute 有使用两种：使用ICMP的和使用UDP的。Microsoft使用ICMP，所以win95上发出的traceRT应使用的是ICMP，但我没有用 sniffer查过；其它包括unix和cisco router都使用UDP.