[SwitchName]ping 1.2.3.4
PING 1.2.3.4: 56 data bytes, press CTRL_C to break
Reply from 1.2.3.4: bytes=56 Sequence=1 ttl=128 time=8 ms
Reply from 1.2.3.4: bytes=56 Sequence=1 ttl=128 time=18 ms (DUP!)
Reply from 1.2.3.4: bytes=56 Sequence=2 ttl=128 time=11 ms
Reply from 1.2.3.4: bytes=56 Sequence=2 ttl=128 time=20 ms (DUP!)
Reply from 1.2.3.4: bytes=56 Sequence=3 ttl=128 time=12 ms
Reply from 1.2.3.4: bytes=56 Sequence=3 ttl=128 time=21 ms (DUP!)
Reply from 1.2.3.4: bytes=56 Sequence=4 ttl=128 time=11 ms
Reply from 1.2.3.4: bytes=56 Sequence=4 ttl=128 time=20 ms (DUP!)
Reply from 1.2.3.4: bytes=56 Sequence=5 ttl=128 time=11 ms
重复DUPLICATE，同一个序号的ICMP包却收到了多个回应。
一般在PING网段广播地址才会出现这种情况，但这里的地址应该不是广播地址，为什么？
1、远端交换机或HUB流量超过负载,即堵塞；重启交换机或者HUB解决。（交换机bug也有可能）
2、IP冲突。这种情况很难得.除非有恶意的行为.故意不回复IP冲突检测的包..
3、路由环路
4、Duplicate packets should never occur, and seem to be caused by nappropriate link-level retransmissions. Duplicates may occur in many situations and are rarely (if ever) a good sign, although the presence of low levels of duplicates may not always be cause for alarm.
5、ARP欺骗，ping中会执行一个ARP过程，如果存在ARP欺骗导致主机收到的MAC地址不断更新。往不同的MAC发送ICMP-Request，但是应该请求包的sequence也会不同吧？
6、这个PING不是WIN系统的，而是类UNIX系统的。一般来说当你在BSD中用PING去PING广播地址时，包将会被复制。
Tags -
交换机 ,
ping ,
(dup!)