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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 21-14 Protocol Stack for FR to Ethernet AToM Bridged Interworking—Without VLAN
Header
FR DLCI to Ethernet VLAN 802.1Q AToM—Bridged Interworking
This interworking type provides interoperability between FR attachment VC and Ethernet VLAN
Attachment VC connected to different PE routers. The bridged encapsulation is used, corresponding to
the Bridged (Ethernet) Interworking mechanism.
The interworking function is performed in the same way as for FR to Ethernet port case, implemented
on the PE connected to the FR attachment VC, based upon a multiprotocol interconnect over Frame
Relay (see
Figure 21-14).
As in the ATM to VLAN case, one difference exists on Ethernet side due the existence of the VLAN
header in the incoming packet. The PE on the VLAN side discards the VLAN header of the incoming
frames from the VLAN CE, and the PE inserts a VLAN header into the Ethernet frames traveling from
the MPLS cloud. The frames sent on the pseudowire (with VC type 5) are Ethernet frames without the
VLAN header.
The Figure 21-15 shows the protocol stack for FR to VLAN AToM Bridged Interworking.
Figure 21-15 Protocol Stack for FR to VLAN AToM Bridged Interworking
270322
FR
CE
FR Link
FR
PE
Eth
PE
Eth
EthernetMPLS Emulated VC of
Q.922 Address
MAC Header
DA
SA
MAC Header
DA
SA
Type/Length Type/Length Type/Length Type/Length
Remainder of
MAC Frame
Remainder of
MAC Frame
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
Control Word
Tunnel Label
VC Label
MAC Header
DA
SA
LAN FCS
270323
FR
CE
FR Link
FR
PE
Eth
PE
VLAN
EthernetMPLS Emulated VC of
Q.922 Address
MAC Header
DA
SA
MAC Header
DA
SA
Type/Length Type/Length Type/Length
Ethertype 81-00
VLAN Tag
Type/Length
Remainder of
MAC Frame
Remainder of
MAC Frame
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
Control Word
Tunnel Label
VC Label
MAC Header
DA
SA
LAN FCS