The network layer generally wants to limit the maximum length of each packet sent. Any time the network layer receives an IP packet to send, it determines which local interface to send the data to and queries that interface to obtain its Maximum Transmission Unit (MTU). The network layer compares the MTU value with the length of the IP packet to be sent. If the length of the IP packet is greater than the MTU value, then the IP packet needs to be fragmented, and the length of the fragmented packe

Before backing up configuration files to an FTP server or client, the following tasks need to be completed: · If the device acts as an FTP client and backs up configuration files to an FTP server, you need to ensure that an FTP connection between the device and the FTP server has been established, for details, see "Configuring the Device as an FTP Client" in CLI Configuration Guide - Basic Configuration.