NETWORKS · VPN · AVANÇADO

IPsec

IKE, Security Associations, ESP, transport/tunnel modes, policy, NAT traversal and VPN troubleshooting.

01 · OVERVIEW

What this topic solves

IKE, Security Associations, ESP, transport/tunnel modes, policy, NAT traversal and VPN troubleshooting.

Core concepts: ipsec, ikev2, esp, vpn, nat-t, child.

02 · MENTAL MODEL

Follow state and packet path

Validate the underlay first, then tunnel negotiation/state, routes, policy, MTU and return path.

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

03 · DESIGN

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.

Operational examples

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.

Initiator                         Responder
 IKE_SA_INIT  ------------------->
              
              <------------------- IKE_AUTH
       IKE SA + primeira Child SA
              ...
       CREATE_CHILD_SA / rekey

/ip/ipsec/peer/print detail
/ip/ipsec/identity/print detail
/ip/ipsec/profile/print detail
/ip/ipsec/proposal/print detail
/ip/ipsec/policy/print detail
/ip/ipsec/active-peers/print detail
/ip/ipsec/installed-sa/print detail
/log/print where topics~"ipsec"

04 · TROUBLESHOOTING

Evidence-driven workflow

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

05 · STANDARDS

IETF IPsec / IKEv2 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.

06 · LAB

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.

07 · CONTINUE