NETWORKS · SWITCHING · AVANÇADO

QinQ and VLAN Tunneling

Provider Bridging, S-TAG/C-TAG, double tagging, MTU and Metro Ethernet service transport.

01 · OVERVIEW

What this topic solves

Provider Bridging, S-TAG/C-TAG, double tagging, MTU and Metro Ethernet service transport.

Core concepts: qinq, 802.1ad, ctag, stag, metro, ethernet, provider, bridging.

02 · MENTAL MODEL

Follow state and packet path

Validate the Layer 2 domain, VLAN/bridge-domain, MAC learning, port state, loops, MTU and counters before changing configuration.

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.

Cliente                 Provedor
[C-TAG 100] → [S-TAG 200][C-TAG 100] → [C-TAG 100]
                  ↑
             domínio S-VLAN

/interface bridge print detail
/interface bridge port print detail
/interface bridge vlan print detail

# Recursos relevantes, conforme modelo/release:
ether-type=0x88a8
tag-stacking=yes
pvid=<S-VLAN>
use-service-tag=yes

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

IEEE 802.1Q Provider Bridging

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