SpanningTree Protocols(xSTP, where the “x” represents the STPtype)—Bridges
functionby associating a MAC address with an interface,similar to the way a router
associatesan IP network address with a next-hopinterface. Just as routing protocols
usepackets to detect and preventrouting loops, bridges use xSTP frames to detect
andprevent bridging loops. (Layer 2 loopsare more devastating to a network because
ofthe broadcast nature of Ethernet LANs.)
Integratedbridging and routing (IRB)—Support for both Layer2 bridging and Layer 3
routingon the same interface. Frames are bridgedif they are not sent to the router's
MACaddress. Frames sent to the router's MACaddress are routed to other interfaces
configuredfor Layer 3 routing.
Related
Documentation
MXSeries Ethernet Services Routers SolutionsPage
ExampleRoadmap: Configuring a Basic Bridge Domain Environmenton page 22
ExampleStep: Configuring Interfacesand VLAN Tags on page 24
ExampleStep: Configuring Bridge Domains on page 30
ExampleStep: Configuring Spanning TreeProtocols on page 32
ExampleStep: Configuring IntegratedBridging and Routing on page 34
ExampleRoadmap: Configuring a Basic Bridge Domain Environment
ConfiguringLayer 2 features on MX Seriesrouters can vary from the very simple
(aggregatedEthernet trunk interfaces,spanning trees), to the more complex (inner and
outerVLAN tags, broadcast domains), to the very complicated(integrated bridging and
routing,Layer 2 filtering). This exampleoffers a fairly complex configurationfor Layer 2
processingin a bridged environment.
ExampleTopologyon page 22
ExampleScenario on page 23
ExampleConfiguration Summary on page 24

ExampleTopology

Considerthe network in Figure 5 on page 23. The figure showsthree MX Series routers
actingas Layer 2 devices.
Copyright© 2010, Juniper Networks,Inc.22
Junos10.4 MX Series Ethernet ServicesRouters Solutions Guide