1-3Figure 1-2 Work flow of automatic configurationStart the devicewithout loading theconfiguration fileThe interface obtainsparameters throughDHCPIs the TFTP server addresscontained in the parameters?YesNoYesNoUnicast a TFTPrequest to obtain theconfiguration fileYesYesBroadcast a TFTPrequest to obtain theconfiguration fileNoRemove the temporaryconfigurations and execute theobtained configuration fileEndIs the TFTP server domainname contained in theparameters?Resolve domain nameof the TFTP serverSucceedsFailsFailsNoRemove the temporaryconfigurations and the devicestarts with null configurationRemove the temporaryconfigurations and the devicestarts with null configurationSucceedsObtaining the IP Address of an Interface and Related Information Through DHCPObtaining an IP addressWhen a device starts up without loading the configuration file, the system automatically configures thefirst active interface (if an active Layer 2 Ethernet interface exists, this first interface is a virtual interfacecorresponding with the default VLAN) of the device as obtaining its IP address through DHCP. Thedevice broadcasts a DHCP request through this interface. The Option 55 field specifies the information(for example, the configuration file name, domain name and IP address of the TFTP server and DNSserver needed for obtaining the automatic configuration files) that the device can obtain from the DHCPserver.Upon successfully obtaining its IP address through DHCP, the device resolves the Option 67 (or the filefield, configuration file name) field, Option 66 (domain name of the TFTP server) field, Option 150 (IPaddress of the TFTP server) field and Option 6 (IP address of the DNS server) field. If failing to obtain itsIP address, the device removes the temporary configuration and starts up without loading theconfiguration file.
