1.2.17. DHCP

A Dynamic Host Configuration Protocol (DHCP) is a network management protocol used for automatically assigning IP addresses to hosts through a remote server.

When a DHCP Server and a DHCP Client are not configured on the same LAN, a DHCP Relay sits between them to forward their messages to each other. The following diagram explains the DHCP information exchange with the help of a DHCP Relay:

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  1. The DHCP Client Broadcasts a Discover message that is forwarded to the DHCP Sever by the DHCP Relay.

  2. The DHCP Server Unicasts an Offer message that is forwarded to the DHCP Client by the DHCP Relay.

  3. The DHCP Client Broadcasts a Request that is forwarded to the DHCP Sever by the DHCP Relay.

  4. The DHCP Server finally unicasts an ACK (acknowledgement) or a NAK (negative acknowledgement) to the Client.

1.2.17.1. DHCP-Helper-Reader

The DHCP-HELPER-READER component reads the DHCP protocol, extracting vital information such as IP-MAC pairs, hostnames, DHCP fingerprinting for device identification, and IP-helper addresses to locate device positions within the network.

OpenNAC never replies to any DHCP request, but this component stores the information for profiling and inventory processes.

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Learn how to configure it, by following its basic and advanced configuration instructions.