This document lists frequently asked questions about the Cisco
7200/7400 in broadband aggregation.
What position does the Cisco 7200/7400 serve in broadband aggregation?
A. The Cisco 7200/7400 serves three roles:
Customer Premises Equipment (CPE) – The Cisco 7200/7400 can be a CPE
device and meet many different requirements.
Network Access Provider (NAP) – Broadband aggregation features
available on the Cisco 7200/7400 allow tunneling of PPP connections from the
customer to the network service provider.
Network Service Provider (NSP) – In addition to tunneling PPP
sessions, the Cisco 7200/7400 can terminate those sessions at their final
What features for broadband aggregation are provided on the Cisco
A. The following features are provided:
Per session rate limiting
CBAC- based firewalling
PPPoE session limit
Subscriber Edge Service Manager (SESM) and Service Selection Gateway
L2TP access concentrator (LAC) and L2TP network server (LNS)
Auto Detect (SNAP) – automatic encapsulation for PPPoA and
PPPoA – allows tunneling and termination of PPP sessions over ATM
permanent virtual circuit (PVC) and switched virtual circuit (SVC)
PPPoE – allows tunneling and termination of PPP sessions over
PPPoEo802.1Q – allows tunneling and termination of Ethernet PPP
sessions across VLAN links.
PPPoEoA – Ethernet PPP connections over ATM links.
PPPoEoE - PPPoE over non-ATM links.
L2TP – provides for tunneling of layer 2 networks over a layer 3
RBE – allows bridged RFC 1483 frames to be routed. Bridge headers are
ignored by the router. This is an alternative to IRB.
Dynamic Subscriber Bandwidth Selection – Dynamically controls
bandwidth at the ATM VC level.
Per VRF AAA for Managed LNS – Permits the Virtual Home Gateway (VHG)
to communicate directly with the customer RADIUS server without having to use a
What broadband aggregation features will be supported in the
A. The following broadband aggregation features will be supported:
Support for the VPN Accelerated Module (VAM) for hardware accelerated
VRF-Lite in Parallel Express Forwarding (PXF)
ATM PVC auto-provisioning via local functionality
How many users/connections will the Cisco 7200/7400 support for broadband
A. A Cisco NPE-400 with 512 MB of memory will support 8,000 sessions and
8,000 L2TP tunnels. An NPE-300 with 256 MB of memory will support 4,000
What is Service Selection Gateway and in what train is it
A. Service Selection Gateway (SSG) is a layer 2 and layer 3 solution that
provides RADIUS authentication and accounting for user interactive policy
routing to different IP destinations (services). SSG allows users to select
where their broadband PPP connections terminate. Normally configured via a
dashboard application, SSG allows the user to select from options such as a
corporate intranet, partner extranet, or public Internet.
SSG is currently supported in Cisco IOS Software Release 12.2(4)B and
What are the plans for supporting more than 8,000
A. The NPE-G1 next generation NPE processor is expected to double the
number of sessions supported.
What broadband features are accelerated in PXF and what Cisco IOS®
Software supports them?
A. The following features were introduced into the PXF with Cisco IOS
Software Release 12.2(4)B.
How does PXF compare to NPE-403 performance?
A. The following increases in performance can be expected with broadband
PPPoA – 65%
PPPoEoA – 120% +
PPPoEoVLAN – 400%
RBE – 100%
What is the Service Path and how is it used for broadband
A. The Service Path is an architecture for making a stack of Cisco 7400s
logically appear as one entity. The product that makes this possible is the
Cisco Network Services (CNS) with support for cluster management. CNS runs on a
dedicated platform (an Internet Engine 2100) and is incorporated into the
architecture of the Service Path.
What are the IDB limits for the Cisco
A. The interface description block (IDB) limit is over 20,000 in Cisco IOS
Software Release 12.3 and later. Refer to
Maximum Number of Interfaces and
Subinterfaces for Cisco IOS Software Platforms: IDB Limits for
How many 802.1Q VLANs does the Cisco 7200/7400 support per
A. The Cisco 7200 and 7400 can support up to 4096 VLANs per interface.
What is a broadband user service license?
A. A broadband user service license (BUS) is a feature license. It should
be purchased when a Cisco 7200 is used to aggregate more than 1000 broadband
How many PVCs can be terminated on the ATM OC3 ports of the Cisco 7200?
A. Each PA-A3 will terminate 4096 PVCs. PA-A6 will support up to 8000
PVCs. For more information, refer to
Understanding the Maximum
Number of Active Virtual Circuits on Cisco ATM Router Interfaces.