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Cisco Catalyst Switch Module 3110 and 3012 for IBM BladeCenter Software Configuration Guide
OL-12189-01
Chapter 3 Assigning the Switch IP Address and Default Gateway
Assigning Switch Information
If the configuration parameters sent to the client in the DHCPOFFER unicast message are invalid (a
configuration error exists), the client returns a DHCPDECLINE broadcast message to the DHCP server.
The DHCP server sends the client a DHCPNAK denial broadcast message, which means that the offered
configuration parameters have not been assigned, that an error has occurred during the negotiation of the
parameters, or that the client has been slow in responding to the DHCPOFFER message (the DHCP
server assigned the parameters to another client).
A DHCP client might receive offers from multiple DHCP or BOOTP servers and can accept any of the
offers; however, the client usually accepts the first offer it receives. The offer from the DHCP server is
not a guarantee that the IP address is allocated to the client; however, the server usually reserves the
address until the client has had a chance to formally request the address. If the switch accepts replies
from a BOOTP server and configures itself, the switch broadcasts, instead of unicasts, TFTP requests to
obtain the switch configuration file.
Configuring DHCP-Based Autoconfiguration
These sections contain this configuration information:
• DHCP Server Configuration Guidelines, page 3-5
• Configuring the TFTP Server, page 3-6
• Configuring the DNS, page 3-6
• Configuring the Relay Device, page 3-7
• Obtaining Configuration Files, page 3-7
• Example Configuration, page 3-8
If your DHCP server is a Cisco device, see the “Configuring DHCP” section of the “IP Addressing and
Services” section of the Cisco IOS IP Configuration Guide, Release 12.2 for additional information
about configuring DHCP.
DHCP Server Configuration Guidelines
Follow these guidelines if you are configuring a device as a DHCP server:
You should configure the DHCP server with reserved leases that are bound to each switch by the switch
hardware address.
If you want the switch to receive IP address information, you must configure the DHCP server with these
lease options:
• IP address of the client (required)
• Subnet mask of the client (required)
• DNS server IP address (optional)
• Router IP address (default gateway address to be used by the switch) (required)
If you want the switch to receive the configuration file from a TFTP server, you must configure the
DHCP server with these lease options:
• TFTP server name (required)
• Boot filename (the name of the configuration file that the client needs) (recommended)
• Hostname (optional)