Cisco 15327 - Manual (Page 294)

18-2
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 18 Configuring Ethernet over MPLS
Understanding EoMPLS
Figure 18-1 EoMPLS Service Provider Network
Implementing EoMPLS on a service provider network requires ML-Series card interfaces to play three
major roles. The ML-Series card interface roles must be configured on both sides of the EoMPLS
point-to-point service crossing the MPLS core.
• ML-Series card interfaces connect the provider’s network directly to the customer edge equipment
and are known as the PE-CLE interfaces. This PE-CLE interface on the ML-Series card is
FastEthernet or GigabitEthernet and is configured to be an endpoint on the EoMPLS point-to-point
session.
• An ML-Series card interface bridges the PE-CLE interface and the RPR network of ML-Series
cards. This RPR/SPR interface contains POS ports and is configured for MPLS IP.
• An ML-Series card interface connects to a core MPLS interface. This interface is GigabitEthernet
or FastEthernet and connects to the port of a Cisco GSR 12000 Series or similar device that is on
the MPLS network. This MPLS cloud-facing interface bridges the SPR interface and the MPLS
cloud.
Implementing EoMPLS across a service provider’s network requires setting up directed Label
Distribution Protocol (LDP) sessions (LSPs) between the ingress and egress PE-CLE routers to
exchange information for a virtual circuit (VC). Each VC consists of two LSPs, one in each direction,
since an LSP is a directed path to carry Layer 2 frames in one direction only.
EoMPLS uses a two-level label stack to transport Layer 2 frames, where the bottom/inner label is the
VC label and the top/outer label is the tunnel label. The VC label is provided to the ingress PE-CLE by
the egress PE-CLE of a particular LSP to direct traffic to a particular egress interface on the egress
PE-CLE. A VC label is assigned by the egress PE-CLE during the VC setup and represents the binding
between the egress interface and a unique and configurative VC ID. During a VC setup, the ingress and
egress PE-CLE exchange VC label bindings for the specified VC ID.
An EoMPLS VC on the ML-Series card can transport an Ethernet port or an IEEE 802.1Q VLAN over
MPLS. A VC type 5 tunnels an Ethernet port and a VC type 4 transports a VLAN over MPLS. In a
VC type 5 session, the user can expect any traffic that is received on an ML-Series card PE-CLE port
with an mpls l2transport route command to be tunneled to the remote egress interface on the far-end
ML-Series card PE-CLE port. With a VC type 4, a user can expect the tunnel to act as physical extension
to that VLAN. The EoMPLS session commands are entered on a VLAN subinterface on the PE-CLE,
and only VLAN-tagged traffic received on that port will be tunneled to the remote PE-CLE.
Core MPLS
RPR RPR
CE CE
PE-CLE PE-CLE
MPLS
Cloud-facing
Interface
MPLS
Cloud-facing
Interface
GSR 12000 GSR 12000
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