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.