H3C Technologies H3C SecBlade NetStream Cards - Manual (Page 219)

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• DNS server—Resolves between IP addresses and host names. In some cases, the device resolves its
IP address to the corresponding host name through the DNS server, and then uses the host name to
request the configuration file with the same name (hostname.cfg) from the TFTP server. If the device
gets the domain name of the TFTP server from the DHCP response, the device can also resolve the
domain name of the TFTP server to the IP address of the TFTP server through the DNS server.
If the DHCP server, TFTP server, DNS server, and the device are not in the same network segment, you
need to configure the DHCP relay agent on the gateway, and configure routing protocols to enable each
server and the device to reach one another.
How automatic configuration works
Automatic configuration works in the following manner:
1. During startup, the device sets the first up interface (if up Layer 2 Ethernet interfaces exist, the VLAN
interface of the default VLAN of the Ethernet interfaces is selected as the first up interface.
Otherwise, the up Layer 3 Ethernet interface with the smallest interface number is selected as the
first up interface) as the DHCP client to request parameters from the DHCP server, such as an IP
address and name of a TFTP server, IP address of a DNS server, and the configuration file name.
2. After getting related parameters, the device sends a TFTP request to obtain the configuration file
from the specified TFTP server and executes the configuration file. If the client cannot get such
parameters, it uses factory default configuration.
NOTE:
•
To implement automatic configuration, you need to configure the DHCP server, DNS server and TFTP
server, but you do not need to perform any configuration on the device that performs automatic
configuration. The configuration of these servers varies with device models and is omitted.
• Before starting the device, connect only the interface needed in automatic configuration to the network.
Work flow of automatic configuration
Figure 64 shows the work flow of automatic configuration.