思考题1 如何ping超过2000的大包

[Kang]

请作实验观察下面的现象：
网络拓扑自己设计，两台设备直接连接即可。

(1)正常的ping 2000字节的大包
r1#ping
Protocol [ip]:
Target IP address: 192.168.1.1
Repeat count [5]:
Datagram size [100]: 2000
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 2000-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 516/517/520
ms
显然可以正常通过

(2)设置了DF位后ping 2000字节的大包
r1#ping
Protocol [ip]:
Target IP address: 192.168.1.1
Repeat count [5]:
Datagram size [100]: 2000
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: yes
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 2000-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
Packet sent with the DF bit set
.....
Success rate is 0 percent (0/5)

请解释为什么会有这样的现象？如何能在设置DF位的时候仍然可以ping到对端的接口地址192.168.1.1？

[常彬]

不知道第二个问题的答案，请赐教！

[Kang Liu]

今天上课简单的讲过，思路是调整MTU。谁能给出具体的解决办法？

Kang

[Scalpel...@gmail.com]

Kang Liu wrote:
> 今天上课简单的讲过，思路是调整MTU。谁能给出具体的解决办法？
>
> Kang

我试过了,在端口模式下直接打mtu XXXX,其中XXXX要>2000
两边都要打,两边设置可以不一样,但必须都>2000

[Kang Liu]

假如两边不一样会出现什么问题呢？这个有没有思考过？