web analytics

Ethernet WANs that Create a Layer 2 Service

The WAN services implied by Figure 3-9 include a broad number of services, with a lot
of complex networking concepts needed to understand those services. Yet, we sit here
at the third chapter of what is probably your first Cisco certification book, so clearly,
getting into depth on these WAN services makes little sense. So, this book focuses on
one specific Ethernet WAN service that can be easily understood if you understand how
Ethernet LANs work.

NOTE For perspective about the broad world of the service provider network shown in
Figure 3-9, look for more information about the Cisco CCNA, CCNP, and CCIE Service
Provider certifications. See www.cisco.com/go/certifications for more details.

The one Ethernet WAN service goes by two names: Ethernet emulation and Ethernet over
MPLS (EoMPLS). Ethernet emulation is a general term, meaning that the service acts like
one Ethernet link. EoMPLS refers to Multiprotocol Label Switching (MPLS), which is one
technology that can be used inside the SP’s cloud. This book will refer to this specific service
either as Ethernet emulation or EoMPLS.

The type of EoMPLS service discussed in this book gives the customer an Ethernet link
between two sites. In other words, the EoMPLS service provides
■ A point-to-point connection between two customer devices
■ Behavior as if a fiber Ethernet link existed between the two devices

So, if you can imagine two routers, with a single Ethernet link between the two routers, you
understand what this particular EoMPLS service does.

Figure 3-10 shows the idea. In this case, the two routers, R1 and R2, connect with an
EoMPLS service instead of a serial link. The routers use Ethernet interfaces, and they can
send data in both directions at the same time. Physically, each router actually connects to
some SP PoP, as shown earlier in Figure 3-9, but logically, the two routers can send Ethernet
frames to each other over the link.
Free CISCO CCNA Routing and Switching ICND1 Study Guide
Figure 3-10 EoMPLS Acting Like a Simple Ethernet Link Between Two Routers

Subscribe To Get

Latest IT certification News 

Help You Pass Any IT Exam