Obtaining The Ip Address Of An Interface And Related Information Through Dhcp - 3Com 4500G Family Configuration Manual

Figure 1-2 Work flow of automatic configuration
Fails
Remove the temporary
configurations and the device
starts with null configuration

Obtaining the IP Address of an Interface and Related Information Through DHCP

Obtaining an IP address
When a device starts up without loading the configuration file, the system automatically configures the
first active interface (if an active Layer 2 Ethernet interface exists, this first interface is a virtual interface
corresponding with the default VLAN) 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.
Upon 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 file.
Start the device
without loading the
configuration file
No
The interface obtains
parameters through
DHCP
Yes
No
Is the TFTP server address
contained in the parameters?
Yes
Is the TFTP server domain
name contained in the
parameters?
Resolve domain name
of the TFTP server
Unicast a TFTP
request to obtain the
configuration file
Succeeds
Remove the temporary
configurations and execute the
obtained configuration file
End
No
Yes
No
Broadcast a TFTP
request to obtain the
configuration file
Yes
Remove the temporary
configurations and the device
starts with null configuration
1-3
Fails
Succeeds