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20-5
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 20 Configuring L2 Virtual Private Networks
Restrictions for L2VPN
Restrictions for L2VPN
The L2VPN feature has the following restrictions:
• Address format: Configure the LDP router ID on all PE routers to be a loopback address with a
/32
mask. Otherwise, some configurations might not function properly.
• The size of maximum transmission unit (MTU) must be the same at both ends of the circuit. To
avoid fragmentation of the packets along the way, ensure that the size of MTU at both end of the
circuit is smaller than the size of MTU in the core.
• The following L2VPN features are not supported:
–
ATM cell switching of any kind
–
ATM AAL5 PDU mode
–
Fragmentation and reassembly, as defined in “PWE3 Fragmentation and Reassembly,”
draft-ietf-pwe3-fragmentation-05.txt, February 2004
–
Sequence number support in the control word
–
Tunnel stitching
–
Pseudowire termination
Standards and RFCs
L2VPN conforms to the industry standards and RFCs listed in Table 20-2.
Table 20-2 Standards and RFCs Supported by L2VPN
Standard or RFC Title
draft-martini-l2circuit-trans-mpls-08.txt Transport of Layer 2 Frames over MPLS
draft-martini-l2circuit-encap-mpls-04.txt Encapsulation Methods for Transport of Layer 2
Frames over MPLS
RFC 3032 MPLS Label Stack Encoding
RFC 3036 LDP Specification