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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 21-10 Protocol Stack for FR to Ethernet Local Switching Bridged Interworking—With VLAN
Header
In Cisco IOS Release 12.2(33)SB, the Ethernet/VLAN to Frame Relay AToM has the following
restrictions:
• The following translations are only supported and other translations are dropped:
–
Ethernet without LAN FCS (0300800080C20007)
–
Spanning tree (0300800080C2000E)
• The PE router automatically supports translation of both Cisco and IETF FR encapsulation types
coming 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 upon receipt even if it
is configured to send a Cisco encapsulation.
• The PVC status signaling works the same way as in the like-to-like case. The PE router reports the
PVC status to the CE router based upon the availability of the pseudowire.
• The attachment circuit maximum transmission unit (MTU) must match when connected over MPLS.
• Only FR DLCI mode is supported. FR port mode is not supported.
• If the Ethernet frame includes a 802.1Q header (VLAN header), due to the type of endpoint
attachment (Ethernet port mode), the VLAN header stays in the frame across the pseudowire
(
Figure 21-11).
• FR encapsulation types supported for routed interworking are Cisco and IETF for incoming traffic.
However, IETF is also supported for outgoing traffic traveling to the CE only.
270317
FR
CE
Eth
CE
FR Ethernet
PE
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
LAN FCSFCS
Ctrl (03) Pad (00)
NLPD (80) OUI (00)
OUI (80-C2)
PID (00-07)