Cisco Cisco Packet Data Interworking Function (PDIF) Guide De Dépannage
L2TP Network Server
▀ LNS Service Operation
▄ Cisco ASR 5000 Series Enhanced Feature Configuration Guide
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Figure 36. Call Processing Using a Single Source and Destination Context
Source
Ctx.
P
D
N
D
N
LNS-
Service
AAA Cfg.
AAA
Local Ctx.
Destination
Ctx.
Def. Sub.
IP Address
Pools
P
D
N
D
N
Packet Data Network
AAA Server
LAC
Interface
Service or
Configuration (Cfg.)
Configuration (Cfg.)
Context (Ctx.)
Packet Data Network
1
6
5
7
2
4
3
LNS
1. An L2TP tunnel request from a peer LAC is received by the LNS service. The tunnel is to facilitate a subscriber
session.
2. The LAC and LNS establish the L2TP tunnel according to the procedures defined in RFC 2661.
Once the L2TP tunnel is established, subscriber L2TP sessions can be established.
3. The LNS service determines which context to use in providing AAA functionality for the subscriber session if
authentication is enabled for the LNS service. For more information on this process, refer How the System
Selects Contexts in System Administration Guide.
For this example, the result of this process is that LNS service determined that AAA functionality should be
provided by the Source context.
Selects Contexts in System Administration Guide.
For this example, the result of this process is that LNS service determined that AAA functionality should be
provided by the Source context.
4. The system communicates with the AAA server specified in the Source context‘s AAA configuration to
authenticate the subscriber.
5. Upon successful authentication, the LNS service terminates the subscriber‘s PPP datagrams from the L2TP
session and the system determines which egress context to use for the subscriber session. For more information
on egress context selection process, refer How the System Selects Contexts in System Administration Guide.
on egress context selection process, refer How the System Selects Contexts in System Administration Guide.