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DGS-1520 Series Gigabit Ethernet Smart Managed Switch Web UI Reference Guide
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The Switch will always check the downloaded firmware. If the version is the same as the current running firmware, the
Switch will terminate the auto-image process. The downloaded configuration, however, will still be executed if the
auto-configuration feature is also enabled.
This function is similar to the auto-configuration function. Both the image file and the configuration file must be placed
on the same TFTP server, as the DHCP option fields are not only used in the auto-image feature, but also in the auto-
configuration feature. The TFTP server IP address is still placed in the DHCP siaddr fields Option 66 or Option 150. If
Option 66, Option 150 and the siaddr fields exist in the DHCP response message at the same time, the Option 150
will be resolved first. If the system fails to connect to the TFTP server, then the system will resolve the Option 66, and
if the system still fails to connect the TFTP server, the siaddr field is the last choice.
When the Switch uses Option 66 to get the TFTP server name, it resolves Option 6 first to get the DNS server IP
address. If the Switch fails to connect to the DNS server or Option 6 does not exist in the response message, the
Switch will try to connect the DNS server already configured in the system manually.
Option 67 is used to identify the boot file when the 'file' field in the DHCP header has been used for DHCP options.
This can only be used in the DHCP auto-configuration mode and not the DHCP auto-image mode. For more
information, refer to RFC 2132. When specifying the image file name, the DHCP Option 125 (RFC 3925) must be
used. The Switch needs to check the enterprise-number1 field. If the value is not the D-Link vendor ID (171), the
Switch will stop the process. If the Option contains more than one field, only the first entry enterprise-number1 will be
used.
To view the following window, click Management > DHCP Auto Image Settings, as shown below:
Figure 4-67 DHCP Auto Image Settings Window
The fields that can be configured are described below:
Parameter Description
DHCP Auto Image State
Select to enable or disable the DHCP auto-image feature here.
DHCP Auto Image Timeout
Enter the timeout value of the DHCP auto-image feature here. The range is from 1
to 65535 seconds.
Click the Apply button to accept the changes made.
DNS
The Domain Name System (DNS) is used to map human-readable domain names to the IP addresses used by
computers to communicate. A DNS server performs name-to-address translation, and may need to contact several
name servers to translate a domain to an address. The address of the machine that supplies domain name service is
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