Cisco Cisco IOS Software Release 12.0(23)S

Before you configure an Xconnect attachment circuit for a CE device (see the section “

”), the CEF feature must be enabled. To enable CEF on an 

interface, use the ip cef or ip cef distributed command.

You must configure a loopback interface on the router for originating and terminating the L2TPv3 
traffic. The loopback interface must have an IP address that is reachable from the remote PE device 
at the other end of an L2TPv3 control channel.

To enable SNMP notifications of L2TP session up and down events, enter the snmp-server enable 
traps l2tun session command before configuring L2TPv3.

See the following sections for configuration tasks for the L2TPv3 feature. Each task in the list is 
identified as either required or optional.

 (optional)

 (required)

 (required)

 (optional)

 (optional)

The L2TP class configuration procedure creates a template of L2TP control channel parameters that can 
be inherited by different pseudowire classes. L2TP control channel parameters are used in control 
channel authentication, keepalive messages, and control channel negotiation. In an L2TPv3 session, the 
same L2TP class must be specified in the pseudowire configured on the PE router at each end of the 
control channel. Configuring L2TP control channel parameters is optional. However, the L2TP class 
must be configured before it is with associated a pseudowire class (see the section “

”).

The three main groups of L2TP control channel parameters that you can configure in an L2TP class are 
described in the following sections:

After you enter L2TP class configuration mode, you can configure L2TP control channel parameters in 
any order. If you have multiple authentication requirements you can configure multiple sets of L2TP 
class control channel parameters with different L2TP class names. However, only one set of L2TP class 
control channel parameters can be applied to a connection between any pair of IP addresses.