Manual

Layer 2 Tunnel Protocol Version 3

Information About Layer 2 Tunnel Protocol Version 3

Cisco IOS Releases 12.0(29)S and 12.2(25)S

OAM Local Emulation Mode

In OAM Local Emulation mode, OAM cells are not passed through the pseudowire. All F5 OAM cells

are terminated and handled locally. On the L2TPv3-based pseudowire, the CE device sends an SLI

message across the pseudowire to notify the peer PE node about the defect, rather than tearing down the

session. The defect can occur at any point in the link between the local CE and the PE. OAM

management can also be enabled on the PE node using existing OAM management configurations.

IPv6 Protocol Demultiplexing

Upgrading a service provider network to support IPv6 is a long and expensive process. As an interim

solution, the Protocol Demultiplexing for L2TPv3 feature introduces the ability to provide native IPv6

support by setting up a specialized IPv6 network and offloading IPv6 traffic from the IPv4 network. IPv6

traffic is transparently tunneled to the IPv6 network using L2TPv3 pseudowires without affecting the

configuration of the CE routers. IPv4 traffic is routed as usual within the IPv4 network, maintaining the

existing performance and reliability of the IPv4 network.

Figure 3 shows a network deployment that offloads IPv6 traffic from the IPv4 network to a specialized

IPv6 network. The PE routers demultiplex the IPv6 traffic from the IPv4 traffic. IPv6 traffic is routed to

the IPv6 network over an L2TPv3 pseudowire, while IPv4 traffic is routed normally. The IPv4 PE routers

must be configured to demultiplex incoming IPv6 traffic from IPv4 traffic. The PE routers facing the

IPv6 network do not require demultiplexing configuration.

Figure 3 Protocol Demultiplexing of IPv6 Traffic from IPv4 Traffic

IPv6 protocol demultiplexing is supported only for Ethernet and Frame Relay traffic in Cisco IOS

Release 12.0(29)S. Protocol demultiplexing requires supporting the combination of an IP address and an

xconnect command configuration on the IPv4 PE interface. This combination of configurations is not

allowed without enabling protocol demultiplexing, with the exception of switched Frame Relay PVCs.

If no IP address is configured, the protocol demultiplexing configuration is rejected. If an IP address is

configured, the xconnect command configuration is rejected unless protocol demultiplexing is enabled

in xconnect configuration mode before exiting that mode. If an IP address is configured with an

xconnect command configuration and protocol demultiplexing enabled, the IP address cannot be

removed. To change or remove the configured IP address, the xconnect command configuration must

first be disabled.

IPv4/v6 CE IPv4/v6 CEIPv4 PE IPv4 PE

L2TPv3 pseudowire L2TPv3 pseudowire

IPv4 traffic

IPv6 traffic

121105

IPv4 network

IPv6 network

IPv6 PEs