MTU stands for Maximum Transmission Unit 鈥?the largest data packet allowed to be transmitted over a network. The MTU of most network devices is 1500, and its unit is bytes. If your local machine’s MTU is larger than the gateway’s MTU, large packets will be fragmented for transmission, which generates many packet fragments, increases packet loss rate, and reduces network speed.
Setting your local machine’s MTU smaller than or equal to the gateway’s MTU can reduce packet loss. MTU refers to the maximum packet size that can pass through a specific layer of a communication protocol, and this parameter is usually related to the communication interface.
1. Networking Environment
A router connects to a peer device through its POS1/0/0 interface. After using the mtu command to change the POS interface’s MTU value to 1500 bytes, it was found that the MTU value did not take effect.
2. Fault Analysis
1. In the POS interface view, execute shutdown and undo shutdown to restart the POS interface.
2. Execute display interface pos and find that the effective MTU value is still 1492 bytes.
3. Check the peer device and find that the peer POS interface’s MTU value is 1492 bytes. During PPP MRU negotiation, if the MTU values configured on both ends are inconsistent, the negotiation result will follow the end with the smaller MTU value.
3. Fault Handling
Perform the following operations on the router: change the peer POS interface’s MTU value to 1500 bytes and restart the interface. After the configuration is complete, the MTU values on both ends are 1500 bytes, and the fault is resolved.
During PPP MRU negotiation, if the MTU values configured on both ends are inconsistent, the negotiation result will follow the end with the smaller MTU value. This is the same as with Belkin router settings 鈥?packets need to be fragmented