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CHAPTER 2
Basic Layer 2 Features on MX Series
Routers
•
Layer 2 Features for a Bridging Environment on page 21
•
Example Roadmap: Configuring a Basic Bridge Domain Environment on page 22
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Example Step: Configuring Interfaces and VLAN Tags on page 24
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Example Step: Configuring Bridge Domains on page 30
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Example Step: Configuring Spanning Tree Protocols on page 32
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Example Step: Configuring Integrated Bridging and Routing on page 34
Layer 2 Features for a Bridging Environment
You configure MX Series routers exactly as you would any other router running the Junos
OS. That is, all the familiar Layer 3 features and protocols are available on the MX Series
routers. However, you can configure Layer 2 features that are unique to the MX Series
routers. This chapter addresses Layer 2 configuration for the MX Series routers. For
information about configuring Layer 3 features and protocols, as well as comprehensive
information aboutinterfacesand systembasics,please seethe otherJunos configuration
guides.
Configuring Layer 2 features on an MX Series router can vary from the very simple
(aggregated Ethernet trunk interfaces, spanning trees), to the more complex (inner and
outer VLAN tags, broadcast domains), to the very complicated (integrated bridging and
routing, Layer 2 filtering). This chapter offers a fairly complex configuration for Layer 2
processing in a bridged environment.
Generally, there are four things that you must configure in an Layer 2 environment:
•
Interfaces and virtual LAN (VLAN) tags—Layer 2 interfaces are usually various type of
Ethernet links with VLAN tags used to connect to customer devices or other bridges
or routers.
•
Bridge domains—Bridge domains limit the scope of media access control (MAC)
learning (and thereby the size of the MAC table) and also determine where the device
should propagate frames sent to broadcast, unknown unicast, and multicast (BUM)
MAC addresses.
21Copyright © 2010, Juniper Networks, Inc.