Showing results for 
Search instead for 
Did you mean: 

Core issue

When DHCP is not correctly configured, a client may not get a valid IP address when booting up. Therefore, client connectivity may not be established. The most common reason for DHCP failure is a misconfiguration on either the DHCP server or the client. However, some configuration may be required on the switch.


DHCP allows clients or hosts to obtain an IP address automatically on bootup. This allows flexibility for users, who can then connect to the network anywhere within a DHCP domain or scope. Instead of having to statically assign each client with a unique IP address, a network administrator can define ranges of IP addresses on the DHCP server and manage addresses from a central location.

Most DHCP configuration is done on the DHCP server; some configuration is done on the clients. Little is required on the Catalyst switch. However, some configuration may be required on the switch, including the use of an IP helper address.

For more information about DHCP, refer to Configuring DHCP.

For more information about configuring DHCP on Catalyst switches, refer to these documents:

The Catalyst 3550 series has a unique DHCP relay option. For additional information, refer to Configuring the DHCP Option 82 for Subscriber Identification.

For detailed information about DHCP on the Catalyst series, refer to Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks.

Device connected to switch


Cisco IP Phone

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: