394 Auto Image and Configuration Update
Obtaining IP Address Information
DHCP is enabled by default on the Out-of-Band (OOB) interface on N3000
and N4000 switches. DHCP is enabled by default on VLAN 1 on the N2000
switches. If an IP address has not been assigned, the switch issues requests for
an IP address assignment.
A network DHCP server returns the following information:
• IP address and subnet mask to be assigned to the interface
• IP address of a default gateway, if needed for IP communication
After an IP address is assigned to the switch, if a hostname is not already
assigned, Auto Configuration issues a DNS request for the corresponding
hostname. This hostname is also displayed as the CLI prompt (as in response
to the hostname command).
Obtaining Other Dynamic Information
The following information is also processed and may be returned by a
BOOTP or DHCP server:
• Name of configuration file (the

file

field in the DHCP header or option
67) to be downloaded from the TFTP server.
• Identification of the TFTP server providing the file. The TFTP server can
be identified by name or by IP address as follows:
– hostname: DHCP option 66 or the

sname

field in the DHCP header)
– IP address: DHCP option 150 or the

siaddr

field in the DHCP header
When a DHCP OFFER identifies the TFTP server more than once, the
DHCP client selects one of the options in the following order:
sname
, option
66, option 150,
siaddr
. If the TFTP server is identified by hostname, a DNS
server is required to translate the name to an IP address.
The DHCP client on the switch also processes the name of the text file
(option 125, the V-I vendor-specific Information option) which contains the
path to the image file.