DHCP

What this topic solves

Dynamic address assignment, DORA, leases, relay, options, DHCPv6 distinctions and troubleshooting.

Follow state and packet path

Separate IP connectivity from the service itself. Capture the transaction and validate state, timers, relay/proxy functions and security policy.

Input → classification/state → decision → table → next-hop/output → counters

Design before configuration

• Define the failure domain and expected convergence behavior.
• Document addressing, identifiers, timers, MTU and policy boundaries.
• Prefer explicit, observable state over assumptions.
• Plan rollback and out-of-band access before risky changes.

Commands and verification

Command syntax varies by platform and software release. The examples below come from the existing portal content and must be validated against the target platform documentation before production use.

Cliente                         Servidor
   |--- DHCPDISCOVER ------------->|
   ||
   |<-- DHCPACK -------------------|

UDP cliente: 68
UDP servidor: 67

Cliente VLAN 120
    ↓ broadcast
Gateway/Relay 10.120.0.1
    ↓ unicast/relay
Servidor DHCP 10.0.0.20
    ↓
Pool selecionado para a rede do cliente

Evidence-driven workflow

1. Define source, destination, time window and exact symptom.
2. Establish the expected healthy state and compare it with the observed state.
3. Inspect counters, tables, logs and packet captures before resets.
4. Test one hypothesis at a time and prefer reversible changes.
5. Repeat the original test after correction and check side effects.

DHCP / DHCPv6 RFCs

Use the current standard/RFC and the documentation for the exact software release being operated. Vendor syntax is an implementation detail; protocol behavior should be understood independently.

Prove the behavior in a controlled topology

Build the smallest topology that reproduces the mechanism, capture control and data traffic, introduce one deliberate failure and diagnose it before applying the fix.

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