Cisco 10000-2P2-2DC Software Guide - Page 468

Ethernet/VLAN to Frame Relay Interworking Chapter 21 Configuring L2VPN Interworking FR DLCI to VLAN 802.1Q Local Switching-Bridged Interworking This interworking type provides interoperability between Frame Relay Attachment VC and Ethernet VLAN Attachment VC connected to the same PE router. For this interworking type the Bridged Encapsulation is used, corresponding to Bridged (Ethernet) Interworking mechanism. In the case of an Ethernet VLAN attachment, the VLAN ID is a service delimiter, so the VLAN header is not included in the frame to or from the FR CE. • In the VLAN to FR direction, the PE router discards the VLAN header from the Layer 2 packet. The PE router sends the frame to the FR egress interface after encapsulating the L2 packet over FR using Bridged encapsulation. • In the FR to VLAN direction, the FR header and bridged encapsulation are discarded and the L2 packet is sent out with a VLAN header inserted, followed by the destination/source MAC addresses. The protocol stack for FR to Ethernet local switching (bridged interworking) is shown in Figure 21-12. FR DLCI to Ethernet Port AToM-Bridged Interworking This interworking type provides interoperability between FR attachment VC and Ethernet attachment VC connected to different PE routers. Bridged encapsulation is used, corresponding to the Bridged (Ethernet) Interworking mechanism. For an FR to Ethernet Port case, the interworking function is performed at the PE connected to the FR attachment VC based on multiprotocol interconnect over Frame Relay (Figure 21-13). The Interworking is implemented similar to an ATM-to-Ethernet case. Figure 21-13 Network Topology for FR to Ethernet AToM Bridged Interworking DLCI FR Link Pseudowire using EoMPLS Tunnel LSP FR CE PE with interworking function P Router P Router MPLS Network Ethernet Ethernet Link PE Ethernet CE The advantage of this architecture is that the Ethernet PE (connected to the Ethernet segment) operates similarly to Ethernet like-to-like services: a pseudowire label is assigned to the Ethernet port and then the remote Label Distribution Protocol (LDP) session distributes the labels to its peer PE. Ethernet frames are carried through the MPLS network using Ethernet over MPLS (EoMPLS). On the PE with Interworking function, in the direction from the FR segment to MPLS cloud, the bridged encapsulation (FR/SNAP header) is discarded and the Ethernet frame is encapsulated with the labels required to go through the pseudowire using the VC type 5 (Ethernet) (Figure 21-14). In the opposite direction, after the label disposition from the MPLS cloud, Ethernet frames are encapsulated over FR using bridged encapsulation. The Figure 21-14 shows the protocol stack for FR to Ethernet Bridged Interworking. 21-20 Cisco 10000 Series Router Software Configuration Guide OL-2226-23 270321