Cisco Systems 3750E manual Configuring DHCP-Based Autoconfiguration

Chapter 3 Assigning the Switch IP Address and Default Gateway

Assigning Switch Information

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)

Depending on the settings of the DHCP server, the switch can receive IP address information, the configuration file, or both.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 3-5