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Implementing Inter-VLAN Routing

Contents

  1. Inter-VLAN Communication Using an External Router: Router-on-a-Stick
  2. Inter-VLAN Communication Tips
  3. Inter-VLAN Communication on a Multilayer Switch Through a Switch Virtual Interface
  4. Configuration Example: Inter-VLAN Communication
  5. Configuration Example: IPv6 Inter-VLAN Communication

Chapter Description

The CCNP and CCIE Enterprise Core & CCNP Enterprise Advanced Routing Portable Command Guide is a fully updated quick reference resource to help you memorize commands and concepts for CCNP or CCIE certifications. In this sample chapter, you will review information and commands related to implementing inter-VLAN routing.

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CCNP and CCIE Enterprise Core & CCNP Enterprise Advanced Routing Portable Command Guide: All ENCOR (350-401) and ENARSI (300-410) Commands in One Compact, Portable Resource

CCNP and CCIE Enterprise Core & CCNP Enterprise Advanced Routing Portable Command Guide: All ENCOR (350-401) and ENARSI (300-410) Commands in One Compact, Portable Resource

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This chapter provides information and commands concerning the following topics:

  • Inter-VLAN communication using an external router: router-on-a-stick

  • Inter-VLAN communication tips

  • Inter-VLAN communication on a multilayer switch through an SVI

    • Configuring inter-VLAN communication on an L3 switch

  • Removing L2 switchport capability of an interface on an L3 switch

  • Configuration example: inter-VLAN communication

  • Configuration example: IPv6 inter-VLAN communication

Inter-VLAN Communication Using an External Router: Router-on-a-Stick

Router(config)#
interface
fastethernet 0/0

Moves to interface configuration mode

 
Router(config-if)# no
shutdown

Enables the interface

 
Router(config-if)#
interface fastethernet
0/0.1

Creates subinterface 0/0.1 and moves to subinterface configuration mode

 
Router(config-subif)#
description Management
VLAN 1

(Optional) Sets the locally significant description of the subinterface

NOTE

Best practices dictate that VLAN 1 should not be used for management or native traffic. Also, consider using separate VLANs for management and native traffic

 
Router(config-subif)#
encapsulation
dot1q 1 native

Assigns VLAN 1 to this subinterface. VLAN 1 will be the native VLAN. This subinterface uses the 802.1q tagging protocol

 
Router(config-subif)#
ip address 192.168.1.1
255.255.255.0

Assigns the IP address and netmask

 
Router(config-subif)#
interface fastethernet
0/0.10

Creates subinterface 0/0.10 and moves to subinterface configuration mode

 
Router(config-subif)#
description Accounting
VLAN 10

(Optional) Sets the locally significant description of the subinterface

 
Router(config-subif)#
encapsulation dot1q 10

Assigns VLAN 10 to this subinterface. This subinterface uses the 802.1q tagging protocol

 
Router(config-subif)#
ip address 192.168.10.1
255.255.255.0

Assigns the IP address and netmask

 
Router(config-subif)#
end

Returns to interface configuration mode

NOTE

Because the VLAN networks are directly connected to the router, routing between these networks does not require a dynamic routing protocol. However, if the router is configured with a dynamic routing protocol, then these networks should be advertised or redistributed to other routers.

NOTE

Routes to the networks associated with these VLANs appear in the routing table as directly connected networks.

NOTE

In production environments, VLAN 1 should not be used as the management VLAN because it poses a potential security risk; all ports are in VLAN 1 by default, and it is an easy mistake to add a nonmanagement user to the management VLAN.

NOTE

Instead of creating a subinterface for the native VLAN (VLAN 1 in the preceding example), it is possible to use the physical interface for native (untagged) traffic. In other words, the physical interface (FastEthernet0/0) would get IP address 192.168.1.1 255.255.255 and it would handle all VLAN 1 native untagged traffic. You would still create a subinterface for VLAN 10 as previously described.

2. Inter-VLAN Communication Tips | Next Section

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