我有几台运行在Openstack上的虚拟机。我有一台数据网络网关分配到MTU = 1500的交换机上,VM必须运行。MTU 1500:1472字节后的分片数据包
另外在Openstack中,我设置了网络的默认MTU = 1500。
我试图从1500到分组大小的虚拟机到网关(或在同一网络上的任何IP)的交换机,它是拆分数据包。
localhost:~# ping -M do -s 1500 10.4.14.18
PING 10.4.14.18 (10.4.14.18) 1500(1528) bytes of data.
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500)
From 10.4.14.17 icmp_seq=1 Frag needed and DF set (mtu = 1500
相反,如果我与MTU较小(1472),它的工作原理发送数据包,
localhost:~# ping -M do -s 1472 10.4.14.18
PING 10.4.14.18 (10.4.14.18) 1472(1500) bytes of data.
1480 bytes from 10.4.14.18: icmp_seq=1 ttl=64 time=0.965 ms
1480 bytes from 10.4.14.18: icmp_seq=2 ttl=64 time=0.515 ms
^C
--- 10.4.14.18 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1875ms
rtt min/avg/max/mdev = 0.515/0.740/0.965/0.225 ms
我可以看到28个字节的区别,我不明白,在这28个字节正在利用?