3Com MSR 50 Series, Configuration Manual

Page: 2172 / 2443

2172 C
HAPTER
122: A
UTOMATIC
C
ONFIGURATION
device to obtain the configuration files (for example, configuration file name,
domain name and IP address of the TFTP server and DNS server).
2
If the device successfully obtains the IP addresses and the configuration file name
from the DHCP server, it initiates a TFTP request and then obtains the
configuration files from the specified TFTP server. If the device does not obtain the
related information, it starts up without loading the configuration files.
Go to the following sections for the detailed working procedure of automatic
configuration:
■
“Obtaining the IP address of an interface and related information through
DHCP” on page 2172
■
“Obtaining the configuration files from the TFTP server” on page 2173
■
“Sending mode of the TFTP request” on page 2173
■
“Executing the configuration files” on page 2174
n
■
No configuration is needed for automatic configuration on the device which
starts up without loading the configuration files. However, some parameters
must be configured on the DHCP server, DNS sever and TFTP server for the
device to successfully obtain the configuration files. The configuration mode
varies with devices. It is omitted here.
■
If you need to use the automatic configuration function, you are
recommended to connect only the interfaces needed in automatic
configuration to the network.
Obtaining the IP address of an interface and related information through
DHCP
When a device starts up without loading the configuration files, the system
automatically configures the interface which is UP (for example a virtual interface
corresponding with the default VLAN or a Layer 3 Ethernet interface) of the device
as obtaining its IP address through DHCP. The device 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
DNS server needed for obtaining the automatic configuration files) that the device
can obtain from the DHCP server.
If successfully obtaining its IP address through DHCP, the device resolves the
Option 67 (or the file field, configuration file name) field, Option 66 (domain
name of the TFTP server) field, Option 150 (IP address of the TFTP server) field and
Option 6 (IP address of the DNS server) field. If failing to obtain its IP address, the
device removes the temporary configuration and starts up without loading the
configuration files.
n
■
The configuration file name is saved in the Option 67 or file field of the DHCP
response. The device first resolves the Option 67 field; if this field contains the
configuration file name, the device does not resolve the file field; otherwise, it
resolves the file field.
■
Temporary configuration is the configuration on VLAN interface 1 or the first
Ethernet interface when the device starts up without loading the configuration
files and the executed
ip host command when the device is resolving the
network intermediate file. (For the detailed description of the ip host