DHCP Design

You are advised to plan an independent DHCP server for large- and medium-sized campus networks. The DHCP design suggestions are as follows:

• A DHCP server is deployed on the entire campus network to simplify O&M.
• DHCP snooping is configured on access devices to ensure that clients obtain IP addresses from valid DHCP servers to prevent attacks from unauthorized users.
• IP addresses can be assigned dynamically or statically. Network administrators can use either of the two mechanisms to allocate IP addresses to hosts based on network requirements.

  Dynamic allocation: An IP address with a lease is assigned to a host. This mode applies to scenarios where hosts require temporary access or IP addresses are insufficient. For example, IP addresses are allocated to portable computers of employees on business trips and mobile terminals in cafes.

  Static allocation: Fixed IP addresses are assigned to specified hosts. This mode applies to hosts that have special requirements on IP addresses. For example, the file server that provides services for external users and the DNS server require fixed IP addresses.

  In the address pool design, static IP addresses must be filtered out to prevent reserved IP addresses from being allocated.

• The lease needs to be planned based on the online duration of a client. On large- and medium-sized campus networks, a long lease needs to be planned since users in the office zone are online for a long time.

Typically, the DHCP server and hosts on large- and medium-sized campus networks are not on the same network segment. Therefore, you are advised to enable the DHCP relay function on the gateway.