Ubuntu/MTUについて、ここに記述してください。
| /long-message |
How to Change MTU (Maximum Transmission Unit) of network interface in Ubuntu Linux
Default MTU Size for Different Network Topology
Network MTU(Bytes) 16 Mbit/Sec Token Ring 17914 4 Mbits/Sec Token Ring 4464 FDDI 4352 Ethernet 1500 IEEE 802.3/802.2 1492 X.25 576
To change the MTU of an interface on GNU/Linux, you just need to use ifconfig command to do so, like this for example
sudo ifconfig eth0 mtu 1492
Check connectivity using ping
You can verify that the path between two machines has at least the expected MTU using the ping command:
ping -M do -c 4 -s 8972 192.168.0.1
This transmits an ICMP echo request to the specified destination then waits for an ICMP echo reply. As the intention here is to check the behaviour of eth0, it would be best to choose a destination on the same subnet in the first instance. Both machines must have a sufficiently large MTU if the test is to succeed.
The -M do option causes the DF (don't fragment) flag to be set, meaning that the packet should be dropped if it cannot remain in one piece at any point in its journey. The -c option sets the number of pings.
The -s option specifies the number of bytes of padding that should be added to the echo request. In addition to this number there will be 20 bytes for the internet protocol header, and 8 bytes for the ICMP header and timestamp. The amount of padding should therefore be 28 bytes less than the network-layer MTU that you are trying to test (9000 − 28 = 8972).