Cisco 10000 - Manual (Page 186)

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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 5 Configuring the Layer 2 Tunnel Protocol Access Concentrator and Network Server
L2TP Network Server
L2TP Network Server
The Cisco 10000 series router can function as an L2TP network server (LNS). By using the managed
LNS features introduced in Cisco IOS Release 12.2(4)BZ1, the Cisco 10000 series router terminates
L2TP sessions from the LAC and places each session into the appropriate VRF instance based on the
L2TP tunnel the session arrived in. The Cisco 10000 router then routes each session within the VRF to
the destination network.
The LNS is a peer to the LAC and sits on one side of an L2TP tunnel. The LNS routes packets to and
from the LAC and a destination network. Acting as the LNS, you can configure the Cisco 10000 series
router to terminate the PPP sessions and route the client IP packets onto the ISP or corporate network
toward their final destination (see
Figure 1-1 on page 1-3 ). You can also configure the LNS to place the
sessions in VRFs before routing the packets, as shown in Figure 5-3 .
Figure 5-3 Managed LNS Topology
All of a service provider’s subscribers do not share the same L2TP trunk interface. Typically, the
Cisco 10000 router uses virtual local area networks (VLANs) to separate a service provider’s subscriber
traffic. The Cisco 10000 series router can also use permanent virtual circuits (PVCs) or a separate
physical interface for each provider to separate traffic. A virtual template interface configures the user
sessions in a tunnel and applies to all users in the same VRF.
The LNS feature is described in the following topics:
• Virtual Template Interface, page 5-23
• Virtual Routing and Forwarding Instance, page 5-23
• Per VRF AAA, page 5-23
• Private Servers, page 5-24
• RADIUS Attribute Screening, page 5-24
• Packet Fragmentation, page 5-24
Router# show vpdn session Verifies active L2TP sessions in a VPDN environment.
Router# show vpdn tunnel Verifies active L2TP tunnel information in a VPDN environment.
Command Purpose
CPE
PPP in L2TP
sessions
Retail LNS
provider
Provider 1
Provider 2
Provider n
69867
L2TP sessions
are terminated
and placed in a VRF
Wholesale LNS
provider
Cisco 10000 ESR
VRF 1
VRF n
VRF 2
LAC
Access network
(ATM or Ethernet)
IP
transport
network