DHCP DORA Lease Workbench

Step through Discover, Offer, Request, Acknowledge, renewal, relay, and NAK paths

Interactive DHCP DORA animation for learning client bootstrap, broadcast and unicast messages, lease timers, server selection, relay agents, and DHCP NAK behavior.

Animation DHCPv4 DORA Lease Timers

DHCP DORA Lease Workbench

Follow how a client with no address discovers a DHCP server, receives an offer, requests one lease, and receives usable IP configuration. Then test renewal, relay, competing offers, and NAK recovery.

INIT Client state

Discover Current message

8 h Lease duration

Pending Client address

Learning Brief

DHCP solves the bootstrap problem: the client starts without an IP address, so the first exchange relies on broadcasts and temporary identifiers.

DORA Discover, Offer, Request, Acknowledge is the common new-lease path.

Lease The address is temporary. Clients renew at T1 and rebind at T2 if renewal fails.

Scenario

Controls

Lease Hours: 8

Client Type Battery sensor IoT gateway Technician laptop

Message Style

DHCPDISCOVER

Stage 1 of 4

The client has no address, so it broadcasts from 0.0.0.0 to find DHCP servers.

Packet Path

Message Fields

Lease Diagnosis

T1 4 h, T2 7 h

Message Trace

Quick Reference

Discover Client broadcasts from 0.0.0.0:68 to 255.255.255.255:67 to find DHCP servers.

Offer Server proposes an address in yiaddr and includes options such as lease time, subnet mask, router, DNS, and server identifier.

Request Client identifies the selected server and requested address; broadcasting also tells other servers to reclaim unused offers.

Acknowledge Server confirms the lease and full configuration; the client can then use the address after normal checks.

Renew and Rebind T1 is normally 50% of lease time and T2 is normally 87.5% if the server does not provide explicit values.

NAK A DHCPNAK rejects the client address or lease context. The client must stop using that address and return to initialization.

How to Read the Workbench

Packet Path The highlighted node is currently sending or processing the DHCP message.

Message Fields Read the UDP endpoints, source and destination IPs, offered address, transaction ID, and key options for each step.

Lease Bar The first marker is T1 renewal and the second marker is T2 rebinding. Expiration means the client must restart DORA.

Technical Accuracy Notes

Broadcast vs Unicast Initial messages are commonly broadcast because the client lacks a usable address. Some server replies can be unicast when client state and flags allow it.

Relay Agents A relay agent fills gateway-interface information and forwards client broadcasts to a server on another subnet.

Renewal During normal renewal, a bound client can unicast DHCPREQUEST to the original server. Rebinding falls back toward broadcast when renewal fails.

Address Checks Clients may perform conflict detection before using an acknowledged address; this animation focuses on DHCP messages, not ARP probing.

Options Vary Real deployments differ in router, DNS, domain, vendor, and class options. The page shows common instructional fields.

DHCPv4 Scope This page covers DHCPv4 DORA. IPv6 address assignment uses different DHCPv6 and SLAAC mechanisms.

Source Links

DHCP Core Protocol RFC 2131 - Dynamic Host Configuration Protocol

DHCP Options RFC 2132 - DHCP Options and BOOTP Vendor Extensions

Relay Agent Information RFC 3046 - DHCP Relay Agent Information Option