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Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-17
Chapter 16 Configuring MPLS Layer 2 VPNs
Prerequisites for Frame Relay DLCI-to-ATM AAL5SNAP Bridged Interworking
msti 2: root_id 32770.0000.0000.0003, root_cost 0, update_flag 0x0
Router# show spanning-tree pseudo-information 1 interface GigabitEthernet3/0/3
Pseudo id 1:
GigabitEthernet 2/1/0
GigabitEthernet 0/0/1
Prerequisites for Frame Relay DLCI-to-ATM AAL5SNAP Bridged
Interworking
Before you configure the Frame Relay Data Link Connection Identifier (DLCI)-to-ATM AAL5SNAP
Bridged Interworking feature on a router, ensure that the following prerequisites are met:
• Enable frame-relay switching on the Frame Relay provider edge (PE) router.
• Customer edge (CE) routers must support Bridge-group Virtual Interface or Routed Bridge
Encapsulation.
Frame Relay DLCI-to-ATM AAL5SNAP Bridged Interworking
This feature provides interoperability between the ATM attachment VC and Frame Relay attachment VC
connected to different PE routers. This interworking uses the bridged encapsulation corresponding to the
bridged (Ethernet) interworking mechanism. The Ethernet frames are carried through the MPLS network
using Ethernet over MPLS (EoMPLS). This feature is configured only in the bridged mode and not in
the routed mode.
Figure 16-3 shows the interworking function performed in the PE routers that are connected to the ATM
attachment VC and the Frame Relay attachment VC.
Figure 16-3 Network Topology for Frame Relay DLCI-to-ATM AAL5SNAP Bridged Interworking
On the ATM PE router with interworking function, when traffic flows from the ATM segment to MPLS
cloud, the bridged encapsulation (ATM and 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). In
the opposite direction, after the label disposition from the MPLS cloud, the Ethernet frames are
encapsulated over AAL5SNAP using bridged encapsulation.
331935
DLCI
VPI/VCI
ATM Link
Pseudowire using EoMPLS
Pseudowire using EoMPLSPseudowire using EoMPLS
P Router
P Router FR PE
ATM PE
ATM CE
MPLS Network
FR CE
Tunnel LSP
Frame Relay
Link