5-2How Automatic Configuration WorksFigure 5-1 Network diagram for automatic configurationThe Switch 4210 supports automatic configuration. The working process is as follows:1) As shown in the above figure, when the switch starts up, it automatically configures the VLANinterface of the default VLAN (in UP state) as a DHCP client. The DHCP client broadcasts a DHCPrequest. The Option 55 in the request specifies the information the device needs, such as aconfiguration file name and a TFTP server address.2) From the reply returned by the DHCP server, the switch obtains its IP address, a configuration filename (Option 67), the domain name (Option 66) or IP address (Option 150) of a TFTP server thatkeeps the configuration file.3) The switch obtains the configuration file from the TFTP server as follows:z The switch first requests the domain name corresponding to its IP address from the DNS serverand takes the domain name as a configuration file name to get the configuration file from the TFTPserver.z If the switch fails to obtain the domain name from the DNS server, it requests the TFTP server foran intermediate file named netdesc.cfg. If the file contains the host name corresponding to theswitch’s IP address, the switch acquires the configuration file corresponding to the host name fromthe TFTP server. (For example, if the host name is switch1, the corresponding configuration filename is switch1.cfg.)
