- Overview of Dial Interfaces, Controllers, and Lines
- Configuring Asynchronous Lines and Interfaces
- Asynchronous Call Queueing by Role
- Configuring Asynchronous Serial Traffic Over UDP
- Configuring and Managing Integrated Modems
- 1- and 2-Port V.90 Modem WICs for Cisco 2600 and Cisco 3600 Series Multiservice Platforms
- Call Tracker show Commands Extensions
- Cisco NM-8AM-V2 and NM-16AM-V2 Analog Modem Network Modules with V.92
- MICA and NextPort Modem Tech-Support Command Additions
- PIAFS Wireless Data Protocol Version 2.1 for Cisco MICA Modems
- V.92 and V.44 Support for Digital Modems
- V.92 Modem on Hold for Cisco AS5300 and Cisco AS5800 Universal Access Servers
- V.92 Modem on Hold for Cisco AS5350, Cisco AS5400, and Cisco AS5850 Universal Gateways and Cisco AS5800 Universal Access Servers
- V.92 Quick Connect for Cisco AS5300 and Cisco AS5800 Universal Access Servers
- V.92 Quick Connect for Cisco AS5350, Cisco AS5400, and Cisco AS5850 Universal Gateways and Cisco AS5800 Universal Access Servers
- V.92 Reporting Using RADIUS Attribute v.92-info
- Configuring and Managing Cisco Access Servers and Dial Shelves
- Configuring and Managing External Modems
- Modem Signal and Line States
- Creating and Using Modem Chat Scripts
- Cisco Modem User Interface
- Modem Script and System Script Support in Large-Scale Dial-Out
- Leased and Switched BRI Interface for ETSI NET3
- ISDN BCAC and Round-Robin Channel Selection Enhancements
- Configuring Virtual Asynchronous Traffic over ISDN
- Configuring Modem Use over ISDN BRI
- Configuring X.25 on ISDN
- Configuring X.25 on ISDN Using AO/DI
- Configuring ISDN on Cisco 800 Series Routers
- Cisco IOS Software Feature Removal
- Configuring ISDN PRI
- Dialing Number Enhancement
- ISDN BCAC and Round-Robin Channel Selection Enhancements
- Configuring ISDN Special Signaling
- Configuring Network Side ISDN PRI Signaling, Trunking, and Switching
- Preparing to Configure DDR
- Configuring Legacy DDR Spokes
- Configuring Legacy DDR Hubs
- Configuring Peer-to-Peer DDR with Dialer Profiles
- Dialer Map VRF-Aware for an MPLS VPN
- Dialer Persistent
- PPPoE Client DDR Idle-Timer
- Redial Enhancements
- Rotating Through Dial Strings
- Configuring Dialer CEF
- CEF Support for Dialer Profiles on Cisco 7500 Routers
- Configuring Snapshot Routing
- Reliable Static Routing Backup Using Object Tracking
- Configuring Dial Backup for Serial Lines
- Configuring Dial Backup Using Dialer Watch
- Dialer Watch Connect Delay
- VRF Aware Dialer Watch
- Configuring Dial Backup with Dialer Profiles
- ISDN Backup in MPLS Core
- Configuring Cisco Easy IP ..
- Configuring Virtual Template Interfaces
- Multiclass Multilink PPP
- Configuring Asynchronous Callback
- Configuring PPP Callback
- Configuring ISDN Caller ID Callback
- Configuring BACP
- Configuring an IP Local Pools Holdback Timer
- Configuring per-User Configuration
- Configuring Resource Pool Management
- Configuring Wholesale Dial Performance Optimization
- Large-Scale Dial-Out
- Dial-Out DS0 Level Trunk Group
- L2TP Large-Scale Dial-Out
- L2TP Large-Scale Dial-Out per-User Attribute via AAA
- Modem Script and System Script Support in Large-Scale Dial-Out
- Large-Scale Dial-Out (LSDO) VRF Aware
- Peer Pool Backup
- Dial Networking Business Applications
- Enterprise Dial Scenarios and Configurations
- Telco and ISP Typical Dial Scenarios and Configurations
- Modem Initialization Strings
- How to Configure Asynchronous Interfaces and Lines
- Interface and Line Configuration Examples
- Line AUX Configuration Example
- Rotary Group Examples
- Dedicated Asynchronous Interface Configuration Example
- Access Restriction on the Asynchronous Interface Example
- Group and Member Asynchronous Interface Examples
- Asynchronous Interface Address Pool Examples
- IP and SLIP Using an Asynchronous Interface Example
- IP and PPP Asynchronous Interface Configuration Example
- Asynchronous Routing and Dynamic Addressing Configuration Example
- TCP Header Compression Configuration Example
- Network Address Conservation Using the ip unnumbered Command Example
- Asynchronous Interface As the Only Network Interface Example
- Routing on a Dedicated Dial-In Router Example
- IGRP Configuration Example
Configuring Asynchronous Lines and Interfaces
This chapter describes how to configure asynchronous line features in the following main sections:
- How to Configure Asynchronous Interfaces and Lines
- How to Configure Other Asynchronous Line and Interface Features
- Configuration Examples for Asynchronous Interfaces and Lines
Perform these tasks, as required, for your particular network.
To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the “Identifying Supported Platforms” section in the “Using Cisco IOS Software” chapter.
For a complete description of the commands in this chapter, refer to the Cisco IOS Dial Technologies Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
How to Configure Asynchronous Interfaces and Lines
To configure an asynchronous interface, perform the tasks described in the following sections as required:
- Configuring a Typical Asynchronous Interface (As required)
- Creating a Group Asynchronous Interface (As required)
- Configuring Asynchronous Rotary Line Queueing (As required)
- Configuring Autoselect (As required)
Configuring a Typical Asynchronous Interface
To configure an asynchronous interface, use the following commands beginning in global configuration mode:
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Brings up a single asynchronous interface and enters interface configuration mode. |
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Enables PPP to run on the asynchronous interfaces in the group. |
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Enables the router to pass routing updates to other routers over the AUX port configured as an asynchronous interface. |
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Places a line into dedicated asynchronous mode using Serial Line Internet Protocol (SLIP) or PPP encapsulation. |
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Specifies that dial-on-demand routing (DDR) is to be supported. |
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Configures a serial interface to call one or multiple sites or to receive calls from multiple sites. |
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Controls access by configuring an interface to belong to a specific dialing group. |
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Enables Challenge Handshake Authentication Protocol (CHAP) and Password Authentication Protocol (PAP) authentication on the interface. Replace the list-name variable with a specified authentication list name.1 |
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The “Interface and Line Configuration Examples” and “Asynchronous Interface As the Only Network Interface Example” sections later in this chapter contain examples of how to configure an asynchronous interface.
Monitoring and Maintaining Asynchronous Connections
This section describes the following monitoring and maintenance tasks that you can perform on asynchronous interfaces:
To monitor and maintain asynchronous activity, use the following commands in privileged EXEC mode as needed:
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Displays parameters that have been set for extended BOOTP requests. |
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To debug asynchronous interfaces, use the following debug command in privileged EXEC mode:
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Displays errors, changes in interface state, and log input and output. |
To debug PPP links, use the following debug commands in privileged EXEC mode as needed:
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Displays errors encountered during remote or local system authentication. |
Creating a Group Asynchronous Interface
Create a group asynchronous interface to project a set of core protocol characteristics to a range of asynchronous interfaces. Configuring the asynchronous interfaces as a group saves you time. Analog modem calls cannot enter the access server without this configuration.
To configure a group asynchronous interface, use the following commands beginning in global configuration mode:
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Brings up a single asynchronous interface and enters interface configuration mode. |
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Router(config-if)#
ip unnumbered loopback
number
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Configures the asynchronous interfaces as unnumbered and assigns the IP address of the loopback interface to them to conserve IP addresses.2 |
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Router(config-if)#
encapsulation ppp
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Enables PPP to run on the asynchronous interfaces in the group. |
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Router(config-if)#
async mode interactive
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Router(config-if)#
ppp authentication chap pap
list-name
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Enables CHAP and PAP authentication on the interface. Replace the list-name variable with a specified authentication list name.3 |
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Router(config-if)#
peer default ip address pool
poolname
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Assigns dial-in clients IP addresses from an address pool.4 |
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Router(config-if)#
no cdp enable
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Disables the Cisco Discovery Protocol (CDP) on the interface. |
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Router(config-if)#
group-range
low-end-of-range high-end-of-range
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Specifies the range of asynchronous interfaces to include in the group, which is usually equal to the number of modems you have in the access server. |
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Router(config-if)#
exit
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The “Group and Member Asynchronous Interface Examples” section later in this chapter contains an example of how to configure a group interface.
Verifying the Group Interface Configuration
To verify the group interface configuration and check if one of the asynchronous interfaces is up, use the show interface async command:
If you are having trouble, enter one of the following debug commands and then send a call into the access server. Interpret the output and make configuration changes accordingly.
Configuring Asynchronous Rotary Line Queueing
The Cisco IOS Asynchronous Rotary Line Queueing feature allows Telnet connection requests to busy asynchronous rotary groups to be queued so that users automatically obtain the next available line, rather than needing to try repeatedly to open a Telnet connection. The Cisco IOS software sends a periodic message to the user to update progress in the connection queue.
This feature allows users to make effective use of the asynchronous rotary groups on a Cisco router to access legacy mainframes or other serial devices with a limited number of asynchronous ports that might be used by a large number of users. Users that are unable to make a Telnet connection on the first attempt are assured of eventual success in an orderly process. They are no longer required to guess when a line might be available and to retry manually again and again.
Connections are authenticated using the method specified for the line configurations for the asynchronous rotary group. If a connection is queued, authentication is done prior to queueing and no authentication is done when the connection is later established.
Make sure you comply with the following requirements when configuring asynchronous rotary line queueing:
- Configure more virtual terminal lines than will ever be used by waiting asynchronous rotary connection attempts. Even when the queue is at its maximum, there must be at least one virtual terminal line available so that system operators or network administrators can use Telnet to access the router to show, debug, or configure system performance.
- When adding lines to a rotary group, all lines must be either queued or not queued. A mixture of queued and unenqueued lines in the same rotary group is not supported and can result in unexpected behavior.
- All lines within a queued rotary group need to use the same authentication method. Using different authentication methods within the same rotary group can result in unexpected behavior.
To configure asynchronous rotary line queueing, use the following commands beginning in global configuration mode:
See the “Rotary Group Examples” section for configuration examples.
Verifying Asynchronous Rotary Line Queueing
To verify operation of asynchronous rotary line queueing, perform the following tasks:
Troubleshooting Asynchronous Rotary Lines
If asynchronous rotary line queueing is not operating correctly, use the following debug commands in privileged EXEC mode to determine where the problem may lie:
Refer to the Cisco IOS Debug Command Reference for information about these commands.
Monitoring and Maintaining Asynchronous Rotary Line Queues
To display queued lines and to remove lines from the queue, use the following commands in EXEC mode as needed:
Configuring Autoselect
Autoselect is used by the access server to sense the protocol being received on an incoming line and to launch the appropriate protocol. Autoselect can be used for AppleTalk Remote Access (ARA), PPP, or SLIP.
When using Autoselect, “login” authentication is bypassed, so if security is required, it must be performed at the protocol level, that is, the AppleTalk Remote Access Protocol (ARAP) or PPP authentication. SLIP does not offer protocol layer authentication.
To configure the Cisco IOS software to allow an ARA, PPP, or SLIP session to start automatically, use the following command in line configuration mode:
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Configures a line to automatically start an ARA, PPP, or SLIP session. |
The autoselect command enables the Cisco IOS software to start a process automatically when a start character is received.
The autoselect command bypasses the login prompt and enables the specified session to begin automatically. However, when the autoselect command is entered with the during login keyword, the username or password prompt appears without the need to press the Return key; thus “login” users will get a prompt right away without needing to press the Return key. While the username or password prompt is displayed, you can choose either to answer these prompts or to send packets from an autoselected protocol.
Normally a router avoids line and modem noise by clearing the initial data received within the first one or two seconds. However, when the autoselect PPP feature is configured, the router flushes characters initially received and then waits for more traffic. This flush causes timeout problems with applications that send only one carriage return. To ensure that the input data sent by a modem or other asynchronous device is not lost after line activation, enter the flush-at-activation line configuration command.
Note
When the autoselect command is used, the activation character should be set to the default Return, and exec-character-bits should be set to 7. If you change these defaults, the application cannot recognize the activation request.
See the “High-Density Dial-In Solution Using Autoselect and EXEC Control Example” section for an example that makes use of the autoselect feature.
Verifying Autoselect PPP
The following trace appears when the debug modem and debug ppp negotiation commands are enabled. As PPP calls pass through the access server, you should see this output.
When autoselect is used, “login” authentication is bypassed. If security is required, it must be performed at the protocol level (that is, ARAP or PPP authentication). SLIP does not offer protocol layer authentication.
Verifying Autoselect ARA
The following trace appears when the debug modem and debug arap internal commands are enabled. As ARA version 2.0 calls pass through the access server, this output is displayed.
The following trace is for ARA version 1.0 calls:
How to Configure Other Asynchronous Line and Interface Features
This section describes the following asynchronous line and interface configurations:
- Configuring the Auxiliary (AUX) Port
- Establishing and Controlling the EXEC Process
- Enabling Routing on Asynchronous Interfaces
- Configuring Dedicated or Interactive PPP and SLIP Sessions
- Conserving Network Addresses
- Using Advanced Addressing Methods for Remote Devices
- Optimizing Available Bandwidth
Configuring the Auxiliary (AUX) Port
The AUX (auxiliary) port is typically configured as an asynchronous serial interface on routers without built-in asynchronous interfaces. To configure the AUX port as an asynchronous interface, configure it first as an auxiliary line with the line aux 1 global configuration command.
The AUX port sends a data terminal ready (DTR) signal only when a Telnet connection is established. The auxiliary port does not use request to send/clear to send (RTS/CTS) handshaking for flow control. To understand the differences between standard asynchronous interfaces and AUX ports configured as an asynchronous interface, refer to Table 1 . To enable the auxiliary port, use the following command in global configuration mode:
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You cannot use the auxiliary (AUX) port as a second console port. To use the AUX port as a console port, you must order a special cable from your technical support personnel.
On an access server, you can configure any of the available asynchronous interfaces (1 through 8, 16, or 48). The auxiliary port (labeled AUX on the back of the product) can also be configured as an asynchronous serial interface, although performance on the AUX port is much slower than on standard asynchronous interfaces and the port does not support some features.
Table 1 illustrates why asynchronous interfaces permit substantially better performance than AUX ports configured as asynchronous interfaces.
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DMA buffering support5 |
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PPP framing on chip6 |
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IP fast switching7 |
On routers without built-in asynchronous interfaces, only the AUX port can be configured as an asynchronous serial interface. To configure the AUX port as an asynchronous interface, you must also configure it as an auxiliary line with the line aux 1 command. Access servers do not have this restriction. Use the line command with the appropriate line configuration commands for modem control, such as speed.
Only IP packets can be sent across lines configured for SLIP. PPP supports transmission of IP, Internet Packet Exchange (IPX), and AppleTalk packets on an asynchronous serial interface.
See the “Line AUX Configuration Example” section for an example that shows how to configure the AUX port.
Establishing and Controlling the EXEC Process
By default, the Cisco IOS software starts an EXEC process on all lines. However, you can control EXEC processes, as follows:
- Turn the EXEC process on or off. (A serial printer, for example, should not have an EXEC session started.)
- Set the idle terminal timeout interval.
The EXEC command interpreter waits for a specified amount of time to receive user input. If no input is detected, the EXEC facility resumes the current connection. If no connections exist, it returns the terminal to the idle state and disconnects the incoming connection.
To control the EXEC process, use the following commands in line configuration mode:
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See the “High-Density Dial-In Solution Using Autoselect and EXEC Control Example” section for an example of configuring control over the EXEC process.
Enabling Routing on Asynchronous Interfaces
To route IP packets on an asynchronous interface, use one of the following commands in interface configuration mode:
The async dynamic routing command routes IP packets on an asynchronous interface, which permits you to enable the Interior Gateway Routing Protocol (IGRP), Routing Information Protocol (RIP), and Open Shortest Path First (OSPF) routing protocols for use when the user makes a connection using the ppp or slip EXEC commands. The user must, however, specify the /routing keyword at the SLIP or PPP command line.
For asynchronous interfaces in interactive mode, the async default routing command causes the ppp and slip EXEC commands to be interpreted as though the /route switch had been included in the command. For asynchronous interfaces in dedicated mode, the async dynamic routing command enables routing protocols to be used on the line. Without the async default routing command, there is no way to enable the use of routing protocols automatically on a dedicated asynchronous interface.
See the following sections for examples of enabling routing on asynchronous interfaces:
Configuring Dedicated or Interactive PPP and SLIP Sessions
You can configure one or more asynchronous interfaces on your access server (and one on a router) to be in dedicated network interface mode. In dedicated mode, an interface is automatically configured for SLIP or PPP connections. There is no user prompt or EXEC level, and no end-user commands are required to initiate remote-node connections. If you want a line to be used only for SLIP or PPP connections, configure the line for dedicated mode.
In interactive mode, a line can be used to make any type of connection, depending on the EXEC command entered by the user. For example, depending on its configuration, the line could be used for Telnet or XRemote connections, or SLIP or PPP encapsulation. The user is prompted for an EXEC command before a connection is initiated.
You can configure an asynchronous interface to be in dedicated network mode. When the interface is configured for dedicated mode, the end user cannot change the encapsulation method, address, or other parameters.
To configure an interface for dedicated network mode or to return it to interactive mode, use one of the following commands in interface configuration mode:
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By default, no asynchronous mode is configured. In this state, the line is not available for inbound networking because the SLIP and PPP connections are disabled.
See the “Dedicated Asynchronous Interface Configuration Example” section for an example of how to configure a dedicated asynchronous interface.
Conserving Network Addresses
When asynchronous routing is enabled, you might need to conserve network addresses by configuring the asynchronous interfaces as unnumbered. An unnumbered interface does not have an address. Network resources are therefore conserved because fewer network numbers are used and routing tables are smaller.
To configure an unnumbered interface, use the following command in interface configuration mode:
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Conserves IP addresses by configuring the asynchronous interfaces as unnumbered, and assigns the IP address of the interface type that you want to leverage. |
Whenever the unnumbered interface generates a packet (for example, a routing update), it uses the address of the specified interface as the source address of the IP packet. It also uses the address of the specified interface to determine which routing processes are sending updates over the unnumbered interface.
You can use the IP unnumbered feature even if the system on the other end of the asynchronous link does not support it. The IP unnumbered feature is transparent to the other end of the link because each system bases its routing activities on information in the routing updates it receives and on its own interface address.
See the “Network Address Conservation Using the ip unnumbered Command Example” section for an example of how to conserve network addresses.
Using Advanced Addressing Methods for Remote Devices
You can control whether addressing is dynamic (the user specifies the address at the EXEC level when making the connection) or whether default addressing is used (the address is forced by the system). If you specify dynamic addressing, the router must be in interactive mode and the user will enter the address at the EXEC level.
It is common to configure an asynchronous interface to have a default address and to allow dynamic addressing. With this configuration, the choice between the default address or dynamic addressing is made by the users when they enter the slip or ppp EXEC command. If the user enters an address, it is used, and if the user enters the default keyword, the default address is used.
Assigning a Default Asynchronous Address
To assign a permanent default asynchronous address, use the following command in interface configuration mode:
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Use the no form of this command to disable the default address. If the server has been configured to authenticate asynchronous connections, you are prompted for a password after you enter the slip default or ppp default EXEC command before the line is placed into asynchronous mode.
The assigned default address is implemented when the user enters the slip default or ppp default EXEC command. The transaction is validated by the TACACS server, when enabled, and the line is put into network mode using the address that is in the configuration file.
Configuring a default address is useful when the user is not required to know the IP address to gain access to a system (for example, users of a server that is available to many students on a campus). Instead of each user being required to know an IP address, they only need to enter the slip default or ppp default EXEC command and let the server select the address to use.
Allowing an Asynchronous Address to Be Assigned Dynamically
When a line is configured for dynamic assignment of asynchronous addresses, the user enters the slip or ppp EXEC command and is prompted for an address or logical host name. The address is validated by TACACS, when enabled, and the line is assigned the given address and put into asynchronous mode. Assigning asynchronous addresses dynamically is useful when you want to assign set addresses to users. For example, an application on a personal computer that automatically dials in using Serial Line Internet Protocol (SLIP) and polls for electronic mail messages can be set up to dial in periodically and enter the required IP address and password.
To assign asynchronous addresses dynamically, use the following command in interface configuration mode:
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Allows the IP address to be assigned when the protocol is initiated. |
The dynamic addressing features of the internetwork allow packets to get to their destination and back regardless of the access server, router, or network they are sent from. For example, if a host such as a laptop computer moves from place to place, it can keep the same address no matter where it is dialing in from.
Logical host names are first converted to uppercase and then sent to the TACACS server for authentication.
See the following sections for examples of configurations that allow asynchronous addresses to be assigned dynamically:
Optimizing Available Bandwidth
Asynchronous lines have relatively low bandwidth and can easily be overloaded, resulting in slow traffic across these lines.
To optimize available bandwidth, perform either of the following optional tasks:
Configuring Header Compression
One way to optimize available bandwidth is by using TCP header compression. Van Jacobson TCP header compression (defined by RFC 1144) can increase bandwidth availability two- to five-fold when compared to lines not using header compression. Theoretically, it can improve bandwidth availability by a ratio of seven to one.
To configure header compression, use the following command in interface configuration mode:
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Configures Van Jacobson TCP header compression on the asynchronous link. |
Forcing Header Compression at the EXEC Level
On SLIP interfaces, you can force header compression at the EXEC prompt on a line on which header compression has been set to passive. This option allows more efficient use of the available bandwidth and does not require entering privileged configuration mode.
To implement header compression, use the following command in interface configuration mode:
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Allows status of header compression to be assigned at the user level. |
For PPP interfaces, the passive option functions the same as the on option.
See the following sections for examples of header compression:
Configuration Examples for Asynchronous Interfaces and Lines
This section provides the following asynchronous interface configuration examples:
- Interface and Line Configuration Examples
- Line AUX Configuration Example
- Rotary Group Examples
- Dedicated Asynchronous Interface Configuration Example
- Access Restriction on the Asynchronous Interface Example
- Group and Member Asynchronous Interface Examples
- Asynchronous Interface Address Pool Examples
- IP and SLIP Using an Asynchronous Interface Example
- IP and PPP Asynchronous Interface Configuration Example
- Asynchronous Routing and Dynamic Addressing Configuration Example
- TCP Header Compression Configuration Example
- Network Address Conservation Using the ip unnumbered Command Example
- Asynchronous Interface As the Only Network Interface Example
- Routing on a Dedicated Dial-In Router Example
- IGRP Configuration Example
Interface and Line Configuration Examples
Asynchronous Interface Backup DDR Configuration Example
The following is an example of one asynchronous interface configuration on a Cisco AS2511-RJ access server that is used in an asynchronous backup DDR scenario:
Passive Header Compression and Default Address Example
The following configuration shows interface and line configuration. The interface is configured with access lists, passive header compression, and a default address. The line is configured for TACACS authentication.
High-Density Dial-In Solution Using Autoselect and EXEC Control Example
The following example configures a Cisco AS5800 access server, which is used as a high-density dial-in solution:
Asynchronous Line Backup DDR Configuration Example
The following example configures one asynchronous line on a Cisco AS2511-RJ access server that is used in an asynchronous backup DDR scenario:
Line AUX Configuration Example
In the following example, the asynchronous interface corresponds to the AUX port. Use the show line command to determine which asynchronous interface corresponds to the AUX port. The IP address on the AUX ports of both routers are in the same subnet
Rotary Group Examples
The following example establishes a rotary group consisting of virtual terminal lines 2 through 4 and defines a password on those lines. By using Telnet to connect to TCP port 3001, the user gets the next free line in the rotary group. The user need not remember the range of line numbers associated with the password.
The following example enables asynchronous rotary line queueing:
The following example enables asynchronous rotary line queueing using the round-robin algorithm:
Dedicated Asynchronous Interface Configuration Example
The following example shows how to assign an IP address to an asynchronous interface and place the line in dedicated network mode. Setting the stop bit to 1 is a performance enhancement.
Access Restriction on the Asynchronous Interface Example
The following example shows how to allow most terminal users access to anything on the local network, but restrict access to certain servers designated as asynchronous servers:
Group and Member Asynchronous Interface Examples
Asynchronous Group Interface Examples
The following example shows how to create an asynchronous group interface 0 with group interface members 2 through 7, beginning in global configuration mode:
group-range 2 7
The following example shows how you need to configure asynchronous interfaces 1, 2, and 3 separately if you do not have a group interface configured:
The following example configures the same interfaces, but from a single group asynchronous interface:
Modem Asynchronous Group Example
To configure a group asynchronous interface, specify the group async number (an arbitrary number) and the group range (beginning and ending asynchronous interface number).
The following example shows the process of creating and configuring a group asynchronous interface for asynchronous interfaces 1 through 96 on a Cisco AS5300 access server, which is loaded with ninety-six 56K MICA technologies modems:
High-Density Dial-In Solution Using an Asynchronous Group
The following example configures a Cisco AS5800 access server that is used as a high-density dial-in solution:
Asynchronous Interface Address Pool Examples
The following sections provide examples of the use of Dynamic Host Configuration Protocol (DHCP) and local pooling mechanisms:
DHCP Pooling Example
The following global configuration example enables DHCP proxy-client status on all asynchronous interfaces on the access server:
The following global configuration example shows how to specify which DHCP servers are used on your network. You can specify up to four servers using IP addresses or names. If you do not specify servers, the default is to use the IP limited broadcast address of 255.255.255.255 for transactions with any and all discovered DHCP servers.
The following interface configuration example illustrates how to disable DHCP proxy-client functionality on asynchronous interface 1:
Local Pooling Example
The following example shows how to select the IP pooling mechanism and how to create a pool of local IP addresses that are used when a client dials in on an asynchronous line. The default address pool comprises IP addresses 172.30.0.1 through 172.30.0.28.
! The address pool is named group1 and comprised of addresses.
172.30.0.1 through 172.30.0.28 inclusive
172.30.0.1 172.30.0.28
Configuring Specific IP Addresses for an Interface
The following example shows how to configure the access server so that it will use the default address pool on all interfaces except interface 7, on which it will use an address pool called lass:
IP and SLIP Using an Asynchronous Interface Example
The following example configures IP and SLIP on asynchronous interface 6. The IP address for the interface is assigned to Ethernet 0, interactive mode has been enabled, and the IP address of the client PC running SLIP has been specified.
IP and the appropriate IP routing protocols have already been enabled on the access server or router.
IP and PPP Asynchronous Interface Configuration Example
The following example configures IP and PPP on asynchronous interface 6. The IP address for the interface is assigned to Ethernet 0, interactive mode has been enabled, and the IP address of the client PC running PPP has been specified. IP and the appropriate IP routing protocols have already been enabled on the access server or router.
Asynchronous Routing and Dynamic Addressing Configuration Example
The following example shows a simple configuration that allows routing and dynamic addressing.
With this configuration, if the user specifies /routing in the EXEC slip or ppp command, routing protocols will be sent and received.
TCP Header Compression Configuration Example
The following example configures asynchronous interface 7 with a default IP address, allowing header compression if it is specified in the slip or ppp connection command entered by the user or if the connecting system sends compressed packets.
Network Address Conservation Using the ip unnumbered Command Example
The following example shows how to configure your router for routing using unnumbered interfaces. The source (local) address is shared between the Ethernet 0 and asynchronous 6 interfaces (172.18.1.1). The default remote address is 172.18.1.2.
The following example shows how the IP unnumbered configuration works. Although the user is assigned an address, the system response shows the interface as unnumbered, and the address entered by the user will be used only in response to BOOTP requests.
Asynchronous Interface As the Only Network Interface Example
The following example shows how one of the asynchronous lines can be used as the only network interface. The router is used primarily as a terminal server, but is at a remote location and dials in to the central site for its only network connection.
Routing on a Dedicated Dial-In Router Example
The following example shows how a router is set up as a dedicated dial-in router. Interfaces are configured as IP unnumbered to conserve network resources, primarily IP addresses.
s 10.129.128.2 255.255.255.0
!
! Normally, the routers dialing in will have their own address and not use BOOTP at all.
dress 10.11.11.254
t ip address 10.11.12.16
! understand IGRP. Run IGRP on the Ethernet (and in the local network).
IGRP Configuration Example
In the following example, only the Interior Gateway Routing Protocol (IGRP) TCP/IP routing protocol is running; it is assumed that the systems that are dialing in to use routing will either support IGRP or have some other method (for example, a static default route) of determining that the router is the best place to send most of its packets.
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