Configuring the ECN330-switch
3151553-KDU 137 365 Uen D 2006-06-16
across the MPLS network and virtual channel labels define the entry and exit
points to the customer. The edge switches connected to the service provider’s
network add and remove these labels as appropriate for packet encapsulation.
The MPLS network uses tunnel labels to transport packets between the service
provider’s switches. The egress service provider switch uses the virtual channel
(VC) label to select the outgoing interface for the Ethernet packet. L2MPLS
tunnels are unidirectional. For bi-directional L2MPLS to function properly, one
tunnel must be configured in each direction.
L2MPLS uses a two label stack to transport Layer 2 frames, where the inner
label is the VC label and the outer label is the tunnel label. The point-to-point
virtual channel requires VC endpoints to be configured at the two edge switches.
Only the edge switches at the ingress and egress points of the MPLS backbone
know about the VCs dedicated to transporting Layer 2 traffic. Other routers do
not have table entries for these VCs. This allows two physically separated
customer switches to appear as if they are directly connected on the same
physical LAN.
Figure 127 L2MPLS Functional Concept
Note: The priority bits of an incoming MPLS frame’s VLAN tag are used to
determine the input COS queue. To specify the MPLS EXP bits (experimental
bits used to define Class of Service) for outgoing MPLS frames, first modify the
priority bits of the VLAN tag with the priority commands provided by the
ECN330-switch. The priority bits in the VLAN tag will then be copied to the
outgoing frames as MPLS EXP bits.
MPLS Network
Service Provider
(edge router)
Customer A
(VPN 1)
Customer B
(VPN 5)
Customer A
(VPN 1)
Customer B
(VPN 5)
Service Provider
(edge router)
Service Provider
(edge router)
Service Provider
(edge router)
VC 1
VC 1
VC 5
VC 5
Tunnel A
Tunnel B
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