The set-df command configures the DF (Don't Fragment) field of the test packet. This field prevents packets from being fragmented.
The undo set-df command restores the default setting.
By default, packet fragmentation is allowed.
Usage Scenario
If two hosts need to communicate with each other over multiple networks, the smallest MTU value of the networks is the path MTU value. Packets can be transmitted normally over multiple networks only after the path MTU value is obtained.
If the DF bit of a packet is not configured, and the length of the packet is longer than the MTU value, the packet will be fragmented into several fragments that are shorter than the path MTU value. As a result, the path MTU cannot be detected by sending packets with increasing lengths. To detect the path MTU value, run the set-df command to prohibit packet fragmentation. Then, increase the length of packets sent along the path to find the path MTU value.
Prerequisites
The type of a test instance has been set to Trace using the test-type trace command.
Precautions
The configuration of the DF bit for packets in a running test instance cannot be changed.