The Dynamic Host Configuration Protocol (DHCP) provides an administrator with a framework for passing configurations to DHCP clients on a network. DHCP Options are added configuration parameters that a DHCP server pushes out to DHCP clients. When the DHCP server receives the DHCPREQUEST message from the client, the configuration process enters its final phase. The acknowledgement phase involves sending a DHCPACK packet to the client.
The MX Series Security Appliances and MS Series Switches (with layer 3 routing enabled) have a built-in DHCP service. When enabled, it can provide DHCP to all configured subnets/VLANs, or relay DHCP messages to designated DHCP servers.
When deploying Cisco Phones and Call Manager, it may be desirable for the phones to automatically discover the TFTP server/Call Manager in order to download a configuration. This will happen automatically when phones are in the same broadcast domain as the Call Manager Server. However, if your Call Manager server is in a different network, you may need to specify a TFTP server. This article explains how to specify a TFTP server using DHCP options.
This article will cover a basic example of how layer 3 routing functionality on MS series switches could be implemented. Before proceeding, please refer to theLayer 3 Switch Overview for general information and configuration options.
