NETWORKS · SWITCHING · INTERMEDIÁRIO

Inter-VLAN Routing

Layer 3 communication between VLANs using routed interfaces, SVIs or router-on-a-stick designs.

01 · OVERVIEW

What this topic solves

Layer 3 communication between VLANs using routed interfaces, SVIs or router-on-a-stick designs.

Core concepts: inter, vlan, svi, router, stick, layer3, gateway.

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.

! Router-on-a-stick
interface Gi0/0.10
 encapsulation dot1Q 10
 ip address 10.10.10.1 255.255.255.0

interface Gi0/0.20
 encapsulation dot1Q 20
 ip address 10.20.20.1 255.255.255.0

! SVI em switch L3
ip routing
interface Vlan10
 ip address 10.10.10.1 255.255.255.0
 no shutdown

/interface vlan
add name=vlan10 interface=bridge1 vlan-id=10
add name=vlan20 interface=bridge1 vlan-id=20

/ip address
add address=10.10.10.1/24 interface=vlan10
add address=10.20.20.1/24 interface=vlan20

/ip route print
/interface bridge vlan print detail

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

Standards and RFCs applicable to the technology

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