DHCP Server

With the DHCP Server feature, the switch hosts the server thereby removing the need to deploy an external DHCP server. The hosted DHCP Server has the same basic functionality as a standalone external DHCP server. The switch listens for DHCP requests from clients on the network and assigns IP addresses dynamically from a preconfigured address pool.

Note

DHCP Server information in this section applies to the DHCP Server feature hosted on the switch. If you deploy an external DHCP server, see the documentation that comes with your device.

DHCP Server includes the following support options:

• DHCP Server supports IPv4 deployments. For IPv6-only deployments, you must deploy an external DHCP server on a standalone server or other network device.

• You can deploy DHCP Server with clients that are in the GRT as well as user-defined VRFs.

• You can configure DHCP Server and DHCP Relay to provide DHCP services to clients in local VLANs as well as clients that connect from a remote switch.

• You can configure DHCP Server to listen for DHCP messages or BOOTP messages, or both.

• If the DHCP Server operates in authoritative mode, the server is the sole authority on the network and assigns all IP addresses within that network. In non-authoritative mode, the server listens for DHCP messages and forwards these messages to another server for processing.

  In authoritative mode, the switch rejects INT_REBOOT messages from clients with a DHCP NAK message. In non-authoritative mode, the switch sends a DHCP NAK only if a lease is present for the same client, but using a different IP address.

DHCP Server Options Configuration

You can configure DHCP Server to provide clients with standard options such as DNS, NTP, TFTP servers, boot image files, NetBIOS servers, and with customized non-standard options that the server passes to clients.

DHCP Server contains multiple global configuration parameters, which you can define within scopes such as host, subnet, vendor class, or global.

The switch process the DHCP options in the following order of precedence:

1. host—Host configuration applies only to a specific host.
2. DHCP subnet—DHCP subnet options apply to only those clients within the specified subnet.
3. vendor class—Vendor class options apply to only those clients with a string that matches a specified vendor class identifier (VCI).
4. global—Global options apply to all clients.

DHCP Server builds a cumulative configuration from all scopes but applies precedence rules in instances of conflict.

The following table illustrates the resulting configuration specifically for Host A following inheritance and precedence rules for configured DHCP Server options.

For more information see the following sections:

• DHCP Custom Options
• DHCP Vendor Options