Specifications
Table Of Contents
- Contents
- Preface
- Getting Started
- Basic Router Configuration
- Interface Port Labels
- Viewing the Default Configuration
- Information Needed for Configuration
- Configuring Basic Parameters
- Configuring Static Routes
- Configuring Dynamic Routes
- Configuring Enhanced IGRP
- Basic Router Configuration
- Configuring Your Router for Ethernet and DSL Access
- Sample Network Deployments
- Configuring PPP over Ethernet with NAT
- Configuring PPP over ATM with NAT
- Configuring a LAN with DHCP and VLANs
- Configuring a VPN Using Easy VPN and an IPSec Tunnel
- Configure the IKE Policy
- Configure Group Policy Information
- Apply Mode Configuration to the Crypto Map
- Enable Policy Lookup
- Configure IPSec Transforms and Protocols
- Configure the IPSec Crypto Method and Parameters
- Apply the Crypto Map to the Physical Interface
- Create an Easy VPN Remote Configuration
- Verifying Your Easy VPN Configuration
- Configuration Example
- Configuring VPNs Using an IPSec Tunnel and Generic Routing Encapsulation
- Configuring a Simple Firewall
- Configuring a Wireless LAN Connection
- Sample Configuration
- Configuring Additional Features and Troubleshooting
- Additional Configuration Options
- Configuring Security Features
- Configuring Dial Backup and Remote Management
- Troubleshooting
- Reference Information
- Cisco IOS Software Basic Skills
- Concepts
- ROM Monitor
- Common Port Assignments
B-6
Cisco 1800 Series Integrated Services Routers (Fixed) Software Configuration Guide
OL-6426-02
Appendix B Concepts
Dial Backup
PVC
A PVC is a connection between remote hosts and routers. A PVC is established for each ATM end node
with which the router communicates. The characteristics of the PVC that are established when it is
created are set by the ATM adaptation layer (AAL) and the encapsulation type. An AAL defines the
conversion of user information into cells. An AAL segments upper-layer information into cells at the
transmitter and reassembles the cells at the receiver.
Cisco routers support the AAL5 format, which provides a streamlined data transport service that
functions with less overhead and affords better error detection and correction capabilities than AAL3/4.
AAL5 is typically associated with variable bit rate (VBR) traffic and unspecified bit rate (UBR) traffic.
Cisco 1800 series routers also support AAL1 and 2 formats.
ATM encapsulation is the wrapping of data in a particular protocol header. The type of router to which
you are connecting determines the type of ATM PVC encapsulation types.
The routers support the following encapsulation types for ATM PVCs:
• LLC/SNAP (RFC 1483)
• VC-MUX (RFC 1483)
• PPP (RFC 2364)
Each PVC is considered a complete and separate link to a destination node. Users can encapsulate data
as needed across the connection. The ATM network disregards the contents of the data. The only
requirement is that data be sent to the ATM subsystem of the router in a manner that follows the specific
AAL format.
Dialer Interface
A dialer interface assigns PPP features (such as authentication and IP address assignment method) to a
PVC. Dialer interfaces are used when configuring PPP over ATM.
Dialer interfaces can be configured independently of any physical interface and applied dynamically as
needed.
Dial Backup
Dial backup provides protection against WAN downtime by allowing a user to configure a backup
modem line connection. The following can be used to bring up the dial backup feature in Cisco IOS
software:
• Backup Interface
• Floating Static Routes
• Dialer Watch
Backup Interface
A backup interface is an interface that stays idle until certain circumstances occur, such as WAN
downtime, at which point it is activated. The backup interface can be a physical interface such as a Basic
Rate Interface (BRI), or an assigned backup dialer interface to be used in a dialer pool. While the primary