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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 21 Configuring L2VPN Interworking
Ethernet/VLAN to Frame Relay Interworking
Figure 21-11 Protocol Stack for FR to Ethernet AToM Bridged Interworking—With VLAN Header
FR DLCI to Ethernet Local Switching—Bridged Interworking
This interworking type provides interoperability between Frame Relay attachment VC and Ethernet
attachment VC connected to the same PE router. For this interworking type, Bridged encapsulation is
used, corresponding to Bridged (Ethernet) Interworking mechanism.
• In the Ethernet to FR direction, the PE router forwards the Layer 2 packet without any change to the
egress interface, encapsulating the L2 packet over FR using Bridged encapsulation.
• In the FR to Ethernet direction, the FR header and bridged encapsulation are discarded and the
L2
packet is sent out with Ethernet encapsulation.
Figure 21-12 shows the protocol stack for FR to Ethernet local switching (bridged interworking).
Figure 21-12 Protocol Stack for FR to Ethernet Local Switching Bridged Interworking
The PE router automatically supports translation of both Cisco and IETF FR encapsulation types
traveling from the CE, but translates only to IETF when sending to the CE router. This is not a problem
for the Cisco CE router, because it can manage IETF encapsulation on receipt even if it is configured to
send a Cisco encapsulation.
270318
FR
CE
FR Link
FR
PE
Eth
PE
Eth
CE
Ethernet VLANMPLS Emulated VC of
Q.922 Address
MAC Header
DA
SA
MAC Header
DA
SA
Ethertype 81-00
VLAN Tag
Type/Length
Ethertype 81-00
VLAN Tag
Type/Length
Remainder of
MAC Frame
Remainder of
MAC Frame
FCS
Ctrl (03) Pad (00)
NLPD (80) OUI (00)
OUI (80-C2)
PID (00-07)
Control Word
Tunnel Label
VC Label
MAC Header
DA
SA
Ethertype 81-00
VLAN Tag
Type/Length
Remainder of
MAC Frame
Control Word
Tunnel Label
VC Label
MAC Header
DA
SA
Ethertype 81-00
VLAN Tag
Type/Length
Remainder of
MAC Frame
LAN FCS
270320
FR
CE
Eth
CE
FR Ethernet
PE
Q.922 Address
MAC Header
DA
SA
MAC Header
DA
SA
Type/Length
Ethertype (81-00)
VLAN Tag
Type/Length
Remainder of
MAC Frame
Remainder of
MAC Frame
LAN FCSFCS
Ctrl (03) Pad (00)
NLPD (80) OUI (00)
OUI (80-C2)
PID (00-07)