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CHAPTER
21-1
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
21
Configuring L2VPN Interworking
Interworking is a transforming function that is required to interconnect two heterogeneous alternating
currents (ACs). Several types of interworking functions exist. The function that is used would depend on
the type of ACs being used, the type of data being carried, and the level of functionality required. The
two main L2VPN interworking functions supported in Cisco IOS Software are bridged and routed
interworking.
Layer 2 transport over MPLS and IP already exists for like-to-like attachment circuits, such as
Ethernet-to-Ethernet or PPP-to-PPP. L2VPN Interworking builds on this functionality by allowing
disparate attachment circuits to be connected. An interworking function facilitates the translation
between different Layer 2 encapsulations. In earlier releases, the Cisco 10000 series router supported
only bridged interworking, which is also known as Ethernet interworking. However, from Cisco IOS
Release 12.2(33)XNE, the Cisco 10000 series router also supports routed interworking.
This chapter describes the following L2VPN interworking features:
• Bridged Interworking
• Routed Interworking
Bridged Interworking
Bridged interworking is used when Layer 2 (L2) packets are considered without regard for Layer 3
contents. No routing participation by the Internet Service Provider (ISP) exists. In Cisco IOS Release
12.2(33)SB, the Ethernet (port) over MPLS pseudowire is supported for bridged interworking.
Therefore, this type of interworking function is also called Ethernet Interworking.
In bridged interworking, Ethernet frames that are extracted from the attachment circuit (AC) are sent
over the MPLS pseudowire. In the case of 802.1 Q AC, the VLAN tag is removed. The pseudowire
functions in the Ethernet (VC type 0x0005) like-to-like mode. The interworking function at the Native
Service Processor (NSP) performs the required adaptation based on AC technology. Non-Ethernet
frames are dropped.
The following bridged interworking features are explained in the chapter:
• Ethernet to VLAN—Bridged Interworking, page 21-2
• Ethernet/VLAN to ATM AAL5 Interworking, page 21-5
• Ethernet/VLAN to Frame Relay Interworking, page 21-17
• Verifying L2VPN Interworking, page 21-30