Dial Configuration Guide, Cisco IOS Release 15.5M&T

V.90 Modem Standard

Study Group 16 of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) developed the V.90 modem standard for multimedia systems. The V.90 standard describes a digital modem and analog modem pair for use on the public switched telephone network (PSTN). V.90 modems are designed for connections that are digital at one end and have only one digital-to-analog conversion. The V.90 standard is expected to be widely used for applications such as Internet and online service access. Download speeds of up to 56,000 bits per second (bps) are possible, depending on telephone line conditions, with upload speeds of up to 33,600 bps.

V.110 Bit Rate Adaption Standard

V.110 is a bit rate adaptation standard defined by the ITU that provides a standard method of encapsulating data over global system for mobile telecommunication (GSM) and ISDN networks. V.110 allows for reliable transport of asynchronous or synchronous data. V.110 adapts a low-speed connection to an ISDN B channel allowing the remote station or terminal adapter to use the fast call setup times offered by ISDN. This feature allows V.110 calls to be originated and terminated over ISDN. It also enables GSM wireless connectivity.

V.110, as an alternative to V.120, provides DTE with V-series type interfaces with access to ISDN network by bit stuffing. Many V.110 devices are used in Europe and Japan. In Japan, MICA supports the Personal-Handyphone-System Internet Access Forum Standard (PIAFS) protocol, which is similar to V.110.

The V.110 implementation for calls on MICA modems is managed by special boardware and modem code, along with the appropriate Cisco IOS image, in a manner similar to other modulation standards. This MICA V.110 implementation provides V.110 user rates ranging from 600 bps to 38,400 bps.

V.110 is supported on the following Cisco devices and network modules:

• Cisco AS5300-series access servers
• Cisco 3620, 3640, and 3660 access routers
• NM-6DM, NM-12DM, NM-18DM, NM-24DM, and NM-30DM network modules

The digital signal processors (DSPs) on the board can function as either modems or V.110 terminal adapters (or V.120 terminal adapters for NextPort DSPs). Based on the ISDN Q.931 bearer capability information element, the Cisco IOS software configures the DSP to treat the incoming call as a modem call, a V.110 call, or a V.120 call.

Figure 1 shows a dial-in scenario for how V.110 technology can be used with a stack of Cisco AS5300-series access servers.

Figure 1 V.110 Dial-In Scenario Using a Stack of Cisco AS5300-Series Access Servers

V.120 Bit Rate Adaptation Standard

ITU-T Recommendation V.120 revised by the ITU-T Study Group 14. V.120 describes a standard that can be used for adapting terminals with non-ISDN standard network interfaces to an ISDN. It is intended to be used between two terminal adapter (TA) functional groups, between two ISDN terminal (TE1) functional groups, between a TA and a TE1, or between either a TA or TE1 and an interworking facility inside a public or private ISDN.

V.120 allows for reliable transport of synchronous, asynchronous, or bit transparent data over ISDN bearer channels. Cisco provides three V.120 support features for terminal adapters that do not send the low-layer compatibility fields or bearer capability V.120 information:

• Answer all incoming calls as V.120—Static configuration used when all remote users have asynchronous terminals and need to connect with a vty on the router.
• Automatically detect V.120 encapsulation—Encapsulation dynamically detected and set.
• Enable V.120 support for asynchronous access over ISDN.

For terminal adapters that send the low-layer compatibility or bearer capability V.120 information, mixed V.120 and ISDN calls are supported. No special configuration is required.

V.120 is a digital rate adaptation and cannot be done on NM-AM network module analog modems. MICA DSP firmware does not have the code to terminate V.120 calls.

NextPort supports only a subset of V.120 functionalities that are supported by Cisco IOS software. Therefore, certain V.120 calls still will need to be terminated on the CPU, even if the chassis has available NextPort modems.

Managing SPE Firmware

You can upgrade your modem firmware to the latest NextPort Service Processing Element (SPE) firmware image available from Cisco. The SPE firmware image is usually retrieved from Cisco.com. You must first copy the SPE image from a TFTP server to flash memory using the copy tftp flash command. You then configure the firmware upgrade using the firmware location and firmware upgrade SPE configuration commands. The firmware location command specifies the location of the firmware file and downloads the firmware to an SPE or a range of SPEs, according to the schedule you selected for the firmware upgrade method using the firmware upgrade command.

The modem firmware upgrade commands must be saved into the system configuration using the write memory command; otherwise, at the next reboot downloading of the specified firmware will not occur.

To upgrade SPE firmware, use the following commands:

Note As soon as a firmware file is specified, the downloading begins. Do not specify all modems and then go into an upgrade process on a busy router. The modems that are not busy will all be marked busy and the server will wait until all the modems on each of the given cards are free before upgrading the multiple-port cards. The only way to clear this situation is to start disconnecting users with a clear command. Normally, groups of modems are specified in scripts with the spe slot/spe_begin and slot/spe_end statements, and upgrades are done in a rolling fashion.

Use the show modem version and show spe version commands to verify that the modems are running the portware version you specified.

The following example shows how to enter the SPE configuration mode, set the range of SPEs, specify the firmware file location in flash memory, download the file to the SPEs, and display a status report using the show spe EXEC command:

For information about upgrading Cisco 3600 Series and Cisco 3700 modems, see the Cisco 3600 Series and Cisco 3700 Series Modem Portware Upgrade Configuration Note at the following URL: http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/sw_conf/portware/5257d56k.htm.

Configuring Modems in Cisco Access Servers

To configure modem support for access servers such as the Cisco AS5300 and AS5800, perform the following tasks. The list describes which tasks are required and which are optional but recommended.

• Configuring Modem Lines (Required)
• Verifying the Dial-In Connection (Optional but Recommended)
• Troubleshooting the Dial-In Connection (Optional but Recommended)
• Configuring the Modem Using a Modemcap (Required)
• Configuring the Modem Circuit Interface (Required for Digital Modems)

Configuring Modem Lines

You must configure the modem lines and set the country code to enable asynchronous connections into your access server. To configure the modems and line, use the following commands beginning in global configuration mode:

Verifying the Dial-In Connection

Before configuring any additional protocols for the line such as SLIP, PPP, or ARA, test whether the dial-in connection for the access server and modem are configured correctly for dial-in access,

Note The same configuration issues exist between the client DTE and client modem. Make sure that you have the correct EIA/TIA-232 cabling and modem initialization string for your client modem.

The following is an example of a successful connection from a PC using a known good modem to dial in to a Cisco access server:

Troubleshooting the Dial-In Connection

Depending upon the problems you experience, take the appropriate action:

• If you are having problems making or receiving calls, make sure that you turned on the protocols for connecting to the lines and configured for incoming and outgoing calls.
• If the calls are not coming up at all, turn on modem debugging. Use the the modem debugging commands as follows:

– The debug modem command enables debugging on the modem line.

– The debug modem csm (or debug csm modem) command enables debugging for lines configured for digital modems.

– The debug isdn q931 command enables debugging for lines configured for the ISDN and Signaling System 7 (SS7) Q.931 protocols.

– The debug cas command enables debugging for lines configured for channel-associated signaling (CAS).

Following is a sample of how to enable and then disable Cisco IOS modem debugging commands on a network access server:

• Enter the debug modem ? command for a list of additional modem debugging commands:

• Turn off the messages by entering the no debug modem command.

For more detailed information refer to the TAC Tech Notes document, Troubleshooting Modems, at the following URL: http://www.cisco.com/en/US/partner/tech/tk801/tk36/technologies_tech_note09186a0080094eb9.shtml#

Configuring the Modem Using a Modemcap

Modems are controlled by a series of parameter settings (up to a limit of 128 characters) that are sent to the modem to configure it to interact with a Cisco device in a specified way. The parameter settings are stored in a database called a modem capability (modemcap). The Cisco IOS software contains defined modemcaps that have been found to properly initialize internal modems. Following are the names of some modemcaps available in the Cisco IOS software:

• cisco_v110—Cisco (NEC) internal V.110 TA (AS5200)
• mica—Cisco MICA HMM/DMM internal digital modem
• nextport—Cisco NextPort CSMV/6 internal digital modem
• microcom_hdms—Microcom HDMS chassis
• microcom_mimic—Cisco (Microcom) internal analog modem (NM-AM–2600/3600)
• microcom_server—Cisco (Microcom) V.34/56K internal digital modem (AS5200)

Enter these modemcap names with the modem autoconfigure type command.

For more information on creating and using modemcaps refer to the TAC Tech Notes documentation, Recommended Modemcaps for Internal Digital and Analog Modems on Cisco Access Servers, at the following URL: http://www.cisco.com/en/US/partner/tech/tk801/tk36/technologies_tech_note09186a008009491b.shtml

If your modem is not on this list and if you know what modem initialization string you need to use with it, you can create your own modemcap; see the following procedure, “Using the Modem Autoconfigure Type Modemcap Feature.” To have the Cisco IOS determine what type of modem you have, use the modem autoconfigure discovery command to configure it, as described in the procedure “Using the Modem Autoconfigure Discovery Feature.”

Note When configuring an internal modem, avoid using the Modem Autoconfigure Discovery feature because the feature can misdetect the internal modem type and cause the modem to start working in an unpredictable and unreproducable manner.

Using the Modem Autoconfigure Type Modemcap Feature

If you know what modem initialization string you need to use with your modem, you can create your own modemcap by performing the following steps.

Step 1 Use the modemcap edit command to define your own modemcap entry.

The following example defines modemcap MODEMCAPNAME:

Step 2 Apply the modemcap to the modem lines as shown in the following example:

Note The report that is generated by the debug confmodem command can be misleading for the MICA and NextPort internal modems because these modems do not have Universal Asynchronous Receiver/Transmitter (UART) and exchange data with the CPU at speeds of hundreds of kbps.

Using the Modem Autoconfigure Discovery Feature

If you prefer that the modem software use its autoconfigure mechanism to configure the modem, use the modem autoconfigure discovery command.

The following example shows how to configure modem autoconfigure discovery mode:

Configuring the Modem Circuit Interface

The next task to complete before using the integrated modem is to configure the modem circuit interface. The basic steps are outlined next:

• If the integrated modem is an analog modem, no further configuration is required; modem characteristics are set on the line.
• If the integrated modem is a digital modem, you can configure either the ISDN or CAS, as appropriate.

– For ISDN BRI and PRI, you need to select the switch type and whether ISDN accepts incoming voice or data calls. If you configure a PRI, you will need to configure the T1 or E1 controller.

– Configuring CAS is described in the chapter “Configuring ISDN PRI” in the Signaling Configuration part of this guide.

If you want to configure SS7, refer to Appendix G, “Configuring the Cisco SS7/C7 Dial Access Solution System,” in the Cisco IOS Voice, Video, and Fax Configuration Guide.

Comparison of NextPort SPE and MICA Modem Commands

Table 2 through Table 5 compare the MICA and SPE commands.

Configuring Cisco Integrated Modems Using Modem Attention Commands

This section provides information about using modem attention (AT) command sets to modify modem configuration. It contains the following sections:

• Using Modem Dial Modifiers on Cisco MICA Modems (As required)
• Changing Configurations Manually in Integrated Microcom Modems (As required)
• Configuring Leased-Line Support for Analog Modems (As required)

Using Modem Dial Modifiers on Cisco MICA Modems

Dial modifiers permit multistage dialing for outbound modem calling through public and private switched telephone networks (PSTNs).

Note For additional information about dial modifiers for the MICA modems, search Cisco.com for the publication AT Command Set and Register Summary for MICA Six-Port Modules.

The Cisco NAS Modem Health feature is enabled by arguments to the ATD AT command. The AT prefix informs the network access server modem that commands are being sent to it, and the D (dial string or dial) suffix dials a telephone number, establishing a connection. With NAS Modem Health feature, you can enter the dial modifiers listed in Table 6 after the D in your dial string: X, W, and the comma (,) character. These modifiers had been previously accepted without error but ignored in Cisco MICA modems on Cisco AS5300 and Cisco AS5800 universal access servers.

In the following example dial string, the portion of the string before the X is dialed for the given line type used in your configuration. All digits after the X generate the appropriate DTMF tones.

atdT5550101x,,567

Changing Configurations Manually in Integrated Microcom Modems

You can change the running configuration of an integrated modem by sending individual modem AT commands. Manageable Microcom modems have an out-of-band feature, which is used to poll modem statistics and send AT commands. The Cisco IOS software uses a direct connect session to transfer information through this out-of-band feature. To send AT commands to a Microcom modem, you must permit a direct connect session for a specified modem, open a direct connect session, send AT commands to a modem, and clear the directly connected session from the modem when you are finished.

Open a direct connect session by entering the modem at-mode slot / port command in privileged EXEC mode. From here, you can send AT commands directly from your terminal session window to the internal Microcom modems. Most incoming or outgoing calls on the modems are not interrupted when you open a direct connect session and send AT commands. However, some AT commands interrupt a call—for example, the ATH command, which hangs up a call. Open and close one direct connect session at a time. Note that multiple open sessions slow down modem performance.

Refer to the AT command set that came with your router for a complete list of AT commands that you can send to the modems.

For Microcom modems, you can clear or terminate an active directly connected session in two ways:

• Press Ctrl-C after sending all AT commands as instructed by the system when you enter AT command mode.
• Enter a second Telnet session and execute the clear modem at-mode slot / port EXEC command. This method is used for closing a directly connected session that may have been mistakenly left open by the first Telnet session.

The following example illustrates use of the modem commands.

AT Mode Example for Integrated Modems

To establish a direct connect session to an internal or integrated modem (existing inside the router), such as the connection required for Microcom modems in the Cisco AS5200 access server, open a directly connected session with the modem at-mode command and then send an AT command to the specified modem. For example, the following example sends the AT command at%v to modem 1/1:

The modem responds with “OK” when the AT command you send is received.

Configuring Leased-Line Support for Analog Modems

Analog modems on the NM-8AM and NM-16AM network modules in the Cisco 2600 and 3600 series routers provide two-wire leased-line support for enterprise customers who require point-to-point connections between locations and for enterprise customers with medium to high data transfer requirements without access to other technologies or with access to only low-grade phone lines.

This feature works only with leased lines that provide loop current. Each modem used must have an RJ-11 connection to the PSTN.

Several features enhance the analog modem software:

• 2-wire leased-line support.
• Modem speeds up to 33.6 kbps with support for all current analog modem protocols, compression, and error correction techniques.
• Power-on autoconnect and loopback testing.
• Support for the maximum number of leased-line users without data transmission loss at distances up to 2 to 5 km.
• In-band and out-of-band monitoring.
• Support on all Cisco 2600 and Cisco 3600 series platforms and upgradability using Cisco IOS software.
• Compatibility with other major leased-line modem vendors.

To configure this support, configure one modem AT command (AT&L) and two AT registers with the modemcap entry command for the appropriate leased lines.

For leased line configuration using the AT&L { 0 | 1 | 2 }command:

• 0 —Disables the leased line (enables switched line; default).
• 1 —Enables the leased line. The modem initiates a leased line when dial and answer commands (ATD and ATA) are issued.
• 2 —Enables the leased line. The modem goes off hook automatically after T57 number of seconds in:

– Originate mode if ATS0 is 0.

– Answer mode if ATS0 is not equal to 0.

The following AT registers can also be set:

• AT:T57 —Number of seconds before going off hook in leased-line mode when the command AT&L2 is used (defaults to 6).
• AT:T79 —Number of autoretrains before the modem is disconnected (defaults to 3).

For more information about using the AT command set with the modems on the NM-8AM and NM-16AM network modules in the Cisco 2600 and 3600 series routers, search Cisco.com for the publication AT Command Set and Register Summary for Analog Modem Network Modules.

To configure a modem for leased-line operation, use the following commands in global configuration mode:

The show modemcap command lists all the predefined modem types and any user-defined modemcaps that are currently configured on the router:

• If the leased line has been configured, the modemcap information will be available.
• If the leased line has not been configured, only the predefined modem types will be displayed.

The important setting for leased-line support is what is defined in the modemcap as the key configuration item and its application to the leased line. Consider the following command strings:

AA stands for autoanswer:

• The answering modem AA register is set to 1 (AA=S0=1) so that autoanswer is “on”.
• The originating modem AA register is set to 0 (AA=S0=0) so that autoanswer is “off”.

If the AA feature is used, both the originating and answering modem must be put into leased-line mode with the &L2 AT command.

In the examples, the micro_LL_orig and micro_LL_ans strings are arbitrary text descriptions.

Note For the modemcap entry command, one of the predefined modem types may be used or a completely user-defined modemcap may be created. For leased line, no new modem type was added. Users may create their own modemcaps for leased-line functionality.

To configure the modem for leased-line operation, use the modemcap entry command. For each connection, each modem must be configured as an originator or answerer.

The following example shows modemcaps for a leased-line originator and answerer and their application to specific ports:

Note When Multilink PPP (MLP) is configured on a dialer interface, the dialer configuration has a default value of 2 minutes for dialer idle timeout. For leased-line connections, set the dialer idle timeout to infinity by adding dialer idle-timeout 0 to the configuration.

Verifying the Analog Leased-Line Configuration

The following information is important for verifying or troubleshooting your configuration. The show modem log command displays the progress of leased-line connections. Here is an example log for a leased-line answerer. Note the “LL Answering” state and “LL Answer” in the “Direction” field of the connection report:

Cisco 2600 and 3600 Series Analog Modem Leased-Line Support Examples

In the following examples, one Cisco 3620 router and one Cisco 3640 router are connected back-to-back using leased lines. The Cisco 3620 router has the originating configuration, and the Cisco 3640 router has the answering configuration.

In the dialer interface configuration, the dialer idle-timeout 0 command is added to set the dialer idle timeout to be infinity. Otherwise the leased line will go down and up every 2 minutes because the default dialer interface idle timeout is 2 minutes.

Note Except for passwords and logins, the Cisco IOS command-line interface (CLI) is case-insensitive. For this document, an uppercase “L” has been used in the command examples to avoid confusion with the numeral “1”.

Leased-Line Originating Configuration

Leased-Line Answering Configuration

Configuring Modem Pooling

Modem pooling allows you to control which modem a call connects to, on the basis of dialed number identification service (DNIS). When modem pooling is not used, incoming and outgoing calls are arbitrarily assigned to modems. For example, consider a Cisco AS5300 access server loaded with a 4-port ISDN PRI card. After an analog modem call comes into the first PRI trunk, the call is greeted by a general pool of B channels and a general pool of modems. Any B channel can be connected to any modem in the access server. A random assignment takes place. Modem resources cannot be controlled.

Modem pooling assigns physical modems to a single DNIS. It enables you to create pools of physical modems in one access server, assign a unique DNIS to each modem pool, and set maximum simultaneous connect limits.

This feature is used for physically partitioning or virtually partitioning modems inside one network access server.

Modem pooling offers these benefits:

• A certain number of modem ports can be guaranteed per DNIS.
• Maximum simultaneous connection limits can be set for each DNIS.

The following restrictions apply:

• Modem pooling is not a solution for large-scale dial access. It cannot be used to create virtual modem pools across multiple access servers that are connected. Modem pooling is physically restricted to one access server.
• MICA and Microcom technology modems support modem pooling. However, only MICA modems support modem pooling for CT1 and CE1 configurations using CAS. To use modem pooling with CT1 or CE1 connections, you must reserve at least two modems in the default modem pool. These reserved modems decode DNIS before handing off calls to the modems assigned to modem pools.

If you see many call failures appearing on the access server, try assigning more modems to the default pool. Use the show modem and show modem summary EXEC commands to display the modem call failure and success ratio.

• No MIBs support modem pooling.
• The same DNIS cannot exist in more than one modem pool.

Modem pooling is supported on the Cisco AS5300 access servers. To configure and manage modems, perform the tasks in the following sections; all tasks are optional and depend upon the needs of your system.

• Creating a Modem Pool (Required)
• Verifying Modem Pool Configuration (As required)

Creating a Modem Pool

You must first decide to physically partition or virtually partition your modems. For more information, see the previous section, “Configuring Modem Pooling.” After you have made this decision, create a modem pool for a dial-in service or specific customer by using the following commands beginning in global configuration mode.

Note If you have active modem calls on the access server before using modem pooling, modem pooling gracefully applies itself to the access server. Modem pooling first waits for active calls to hang up before assigning modems to modem pools and directing calls according to DNIS.

Verifying Modem Pool Configuration

To verify the modem configuration, enter the show modem-pool command to display the configuration. This command displays the structure and activity status for all the modem pools in the access server. See Table 7 for a description of each display field.

For modem pool configuration examples, see the section “Physical Partitioning with Dial-In and Dial-Out Scenario” later in this chapter.

Check the following if you are having trouble operating your modem:

• Make sure you have not configured the same DNIS for multiple pools.
• Make sure you have not placed the same modem in multiple pools.

Note Modem pools that use MICA or Microcom modems support incoming analog calls over ISDN PRI. However, only MICA modems support modem pooling for T1 and E1 configurations with CAS.

Configuring Physical Partitioning

You can either physically partition or virtually partition your modems to enable different dial-in and dial-out services. This section provides information about the following optional tasks:

• Creating a Physical Partition
• Physical Partitioning with Dial-In and Dial-Out Scenario

Physical partitioning uses one access server to function as multiple access servers loaded with different types of modem services (for example, V.34 modems, fax-capable modems, and point-of-sale (POS) modems). Each modem service is part of one physical modem pool and is assigned a unique DNIS number. (See Figure 2.)

Figure 2 Modem Pooling Using Physical Partitioning

Physical partitioning can also be used to set up an access server for bidirectional dial access. (See Figure 3.)

Figure 3 shows one Cisco AS5300 access server loaded with 96 MICA modems and configured with 2 modem pools. One modem pool has 84 modems and collects DNIS. This pool is shared by 400 salespeople who remotely download e-mail from headquarters. The other modem pool contains 12 fax-capable modems and does not collect DNIS. This pool is shared by 40 employees using PCs on a LAN. Each time an outbound call is initiated by a PC, a modem on the Cisco AS5300 access server is seized and used to fax out or dial out. Not configuring DNIS support in the fax-out modem pool protects the pool from being used by the calls coming in from the field. Regardless of how many salespeople are dialing in or which telephone number they use, the fax-out and dial-out modem pool will always be reserved for the PCs connected to the LAN.

Figure 3 Modem Pooling Used for Bidirectional Dialing

Creating a Physical Partition

The following task creates one V.34 modem pool and one 56K modem pool on a Cisco AS5200. Each modem pool is configured with its own DNIS. Depending on which DNIS the remote clients dial, they connect to a 56K MICA modem or a V.34 Microcom modem.

The following hardware configuration is used on the Cisco AS5200 access server:

• One 2-port T1 PRI card
• One 48-port card containing four 6-port MICA 56K modem modules and two 12-port Microcom V.34 modem modules

To configure basic physical partitioning, perform the following steps:

Step 1 Enter global configuration mode:

Step 2 Create the modem pool for the 56K MICA modem services using the modem-pool name command. The modem pool is called 56kservices, which spans four 6-port MICA 56K modem modules.

Note The router is in modem pool configuration mode after the prompt changes from Router(config)# to Router(config-modem-pool)#.

Step 3 Assign a range of modems to the modem pool using the pool-range number - number command. Because all the 56K MICA technologies modems are seated in slot 1, they are assigned TTY line numbers 1 to 24. Use the show line EXEC command to determine the TTY line numbering scheme for your access server.

Step 4 Assign a DNIS to the modem pool using the called-number number [ max-conn number ] command. This example uses the DNIS 5550101 to connect to the 56K modems. The maximum simultaneous connection limit is set to 24. The 25th user who dials 5550101 gets a busy signal.

Step 5 Return to EXEC mode by entering Ctrl-Z. Next, display the modem pool configuration using the show modem-pool command. In the following example, 56K modems are in the modem pool called 56kservices. The remaining 24 V.34 Microcom modems are still in the default system pool.

Step 6 Create the modem pool for the Microcom physical partition. After the configuration is complete, the show modem-pool command shows that there are no remaining modems in the system default modem pool.

Physical Partitioning with Dial-In and Dial-Out Scenario

The following is a bidirectional dial scenario using a Cisco AS5300 access server. Two modem pools are configured. One modem pool contains 84 56K MICA modems, which is shared by 400 remote salespeople who dial in to headquarters. The other modem pool contains 12 fax-capable modems, which are shared by 40 employees who dial out of the headquarters LAN using the Cisco DialOut Utility software. See Figure 3 for the network topology.

The following hardware configuration is used on the Cisco AS5300:

• One 4-port T1 PRI card
• Two 48-port cards containing fourteen 6-port MICA 56K modem modules and two 6-port MICA fax-capable modem modules

To configure physical partitioning with dial-in and dial-out capability, perform the following steps:

Step 1 Create the 56K modem pool for the 400 remote salespeople. This modem pool contains 84 modems, which are reserved for the dial-in calls. To get access, the salespeople dial the DNIS 5550303. The total number of simultaneous calls is limited to 84. The 85th call and those above it are rejected. The modem dialin line configuration command is used to prevent modems 1 to 84 from dialing out.

Step 2 Create the dial-out/fax-out modem pool for the 40 local employees connected to the headquarters LAN. This modem pool contains 12 fax-capable MICA modems. No DNIS is assigned to the pool. Because lines 85 to 96 are used for the dial-out and fax-out modem services, the asynchronous lines are configured for reverse Telnet. This configuration is needed for the Telnet extensions to work with the dial-out application, which is installed on the LAN PCs.

Step 3 Configure the group asynchronous interface, which assigns core protocol characteristics to all the asynchronous interfaces in the system. Regardless of the direction that the modems are dialing, all modems in the access server leverage this group asynchronous configuration.

Step 4 Create an IP address pool for all the dial-in clients and dial-out clients. Both types of clients borrow addresses from this shared pool.

Step 5 (Optional) If you are using CiscoSecure AAA and a remote TACACS server, include the following security statements on the access server:

You should also include the host name, timeout interval, and authentication key:

Configuring Virtual Partitioning

Virtual partitioning creates one large modem pool on one access server, but assigns different DNIS numbers to different customers. Each incoming DNIS consumes resources from the same modem pool, but a maximum connect option is set for each DNIS.

Figure 4 shows two Internet service provider (ISP) customers who are leasing modems from another service provider. Each ISP is assigned its own DNIS number and range of modems. Each ISP is guaranteed a certain number of physical modem ports for simultaneous connections. After an ISP uses up all the modems assigned to its DNIS, a busy signal is issued.

Figure 4 Modem Pooling Using Virtual Partitioning

Virtual partitioning essentially resells modem banks to customers, such as a small-sized ISP. However, remember that modem pooling is a single-chassis solution, not a multichassis solution. Modem pooling is not a solution for reselling ports on a large-scale basis.

The following procedure creates one modem pool on a Cisco AS5300 access server for two ISP customers. The shared modem pool is called isp56kpool. However, both ISP customers are assigned different DNIS numbers and are limited to a maximum number of simultaneous connections.

See Figure 4 for the network topology.

The following hardware configuration is used on the Cisco AS5300 access server:

• One 4-port T1 PRI card
• Two 48-port cards containing sixteen 6-port MICA 56K modem modules

To configure virtual partitioning, perform the following steps:

Step 1 Enter global configuration mode:

Step 2 Create the shared modem pool for the 56K MICA modem services. This modem pool is called isp56kpool, which spans sixteen 6-port MICA 56K modem modules.

Step 3 Assign all the modems to the modem pool using the pool-range number - number command. Use the show line EXEC command to determine your TTY line numbering scheme.

Step 4 Assign a unique DNIS to each ISP customer using the called-number number [ max-conn number ] command. In this example, the max-conn number option limits each ISP to 48 simultaneous connections. The 49th user to dial either DNIS will get a busy signal.

Step 5 Return to EXEC mode by entering a Ctrl-Z sequence. Next, display the modem pool configuration using the show modem-pool command. In the following example, all the 56K modems are in the isp56kpool modem pool. The output also shows two DNIS numbers configured: 5550101 and 5550202.

Configuring Call Tracker

The Call Tracker feature captures detailed statistics on the status and progress of active calls and retains historical data for disconnected call sessions. Call Tracker collects session information such as call states and resources, traffic statistics, total bytes transmitted and received, user IP address, and disconnect reason. This data is maintained within the Call Tracker database tables, which are accessible through the Simple Network Management Protocol (SNMP), the CLI, or syslog.

Note The calltracker command, providing Call Tracker services, is supported for dial calls but not voice. Calltracker is supported for dial calls on 5x platforms (5300, 5350, 5400, 5800, and 5850).

Call Tracker is notified of applicable call events by related subsystems such as ISDN, PPP, CSM, Modem, EXEC, or TCP-Clear. SNMP traps are generated at the start of each call, when an entry is created in the active table, and at the end of each call, when an entry is created in the history table. Call Record syslogs are available through configuration that will generate detailed information records for all call terminations. This information can be sent to syslog servers for permanent storage and future analysis.

Additionally, the status and diagnostic data that is routinely collected from MICA modems is expanded to include new link statistics for active calls, such as the attempted transmit and receive rates, the maximum and minimum transmit and receive rates, and locally and remotely issued retrains and speedshift counters. For more detailed information on Call Tracker logs, refer to the TAC Tech Notes document, Understanding Call Tracker Outputs, at the following URL: http://www.cisco.com/warp/public/471/calltracker_view.html

To configure Call Tracker, perform the following steps:

Verifying Call Tracker

To verify the operation of Call Tracker, use the the following command in EXEC mode:

Enabling Call Tracker

The following example shows how to enable the Call Tracker feature:

Configuring Polling of Link Statistics on MICA Modems

The status and diagnostic data that is routinely collected from MICA modems is expanded to include new link statistics for active calls, such as the attempted transmit and receive rates, the maximum and minimum transmit and receive rates, and locally and remotely issued retrains and speedshift counters. This connection data is polled from the modem at user-defined intervals and passed to Call Tracker.

To poll modem link statistics, use the following command in global configuration mode:

Note The modem link-info poll time command consumes a substantial amount of memory, approximately 500 bytes for each MICA modem call. Use this command only if you require the specific data that it collects; for instance, if you have enabled Call Tracker on your access server.

Configuring MICA In-Band Framing Mode Control Messages

Dial-in Internet connections typically start in character mode to allow the user to log in and select a preferred service. When Cisco IOS software determines that the user wants a framed interface protocol during the call, such as PPP or SLIP, commands are sent to the MICA modem so that it will provide hardware assistance with the framing. This hardware assistance reduces the Cisco IOS processing load. To avoid loss or misinterpretation of framed data during the transition, issue these commands at precise times with respect to the data being sent and received.

MICA modem framing commands can be sent in the data stream itself, which greatly simplifies Cisco IOS tasks in achieving precision timing. For PPP connections, the common way for modems to connect to the Internet, total connect time might typically be improved by 2 to 3 seconds. This functionality reduces timeouts during PPP startup and reduces startup time. If an ASCII banner is sent just before PPP startup, this feature eliminates problems with banner corruption such as truncation and extraneous characters, thus improving the performance of terminal equipment.

In earlier software, the modem interface timing rules were not well understood and were difficult or impossible to implement using the separate command interface of the modem. The practical result is that the MICA in-band framing mode reduces the number of timeouts during PPP startup, and thus reduces startup time. MICA in-band framing is supported on MICA modems in Cisco AS5300 and Cisco AS5800 access servers.

To configure the MICA in-band framing mode control messages, use the following commands beginning in global configuration mode:

The Cisco IOS software offers additional interface commands that can be set to control modem interface timing. Refer to the Cisco IOS command references for more information about the interface commands described in the following paragraphs.

When a link goes down and comes back up before the timer set by the carrier-delay command expires, the down state is effectively filtered, and the rest of the software on the switch is not aware that a link-down event occurred. Therefore, a large carrier delay timer results in fewer link-up and link-down events being detected. On the other hand, setting the carrier delay time to 0 means that every link-up and link-down event is detected.

When the link protocol goes down (because of loss of synchronization, for example), the interface hardware is reset and the data terminal ready (DTR) signal is held inactive for at least the specified interval. Setting the pulse-time command enable pulsing DTR signal intervals on serial interfaces, and is useful for handling encrypting or other similar devices that toggle the DTR signal to resynchronize.

Use the modem dtr-delay command to reduce the time that a DTR signal is held down after an asynchronous line clears and before the DTR signal is raised again to accept new calls. Incoming calls may be rejected in heavily loaded systems, even when modems are unused because the default DTR hold-down interval may be too long. The modem dtr-delay command is designed for lines used for an unframed asynchronous session such as Telnet. Lines used for a framed asynchronous session such as PPP should use the pulse-time interface command.

Enabling Modem Polling

The following example enables modem status polling through the out-of-band feature, which is associated to line 1:

Setting Modem Poll Intervals

The following example sets the time interval between polls to 10 seconds using the modem poll time global configuration command:

Setting Modem Poll Retry

The following example configures the server to attempt to retrieve statistics from a local modem up to five times before discontinuing the polling effort:

Collecting Modem Statistics

Depending upon your modem type, the Cisco IOS software provides several show EXEC commands that allow you to display or poll various modem statistics. See Table 2 and Table 3 to find the show EXEC command appropriate for your modem type and the task you want to perform.

Logging EIA/TIA Events

To facilitate meaningful analysis of the modem log, turn the storage of specific types of EIA/TIA events on or off. To activate or inactivate the storage of a specific type of EIA/TIA modem event for a specific line or set of lines, use either of the following commands in line configuration mode, as needed:

Configuring a Microcom Modem to Poll for Statistics

Manageable Microcom modems have an out-of-band feature, which is used for polling modem statistics. To configure the system to poll for modem statistics, use the following commands in global configuration mode:

Troubleshooting Using a Back-to-Back Modem Test Procedure

You can manually isolate an internal back-to-back connection and data transfer between two modems for focused troubleshooting purposes. For example, if mobile users cannot dial in to modem 2/5 (which is the sixth modem port on the modem board in the second chassis slot), attempt a back-to-back test with modem 2/5 and a modem known to be functioning, such as modem 2/6. You might need to enable this command on several different combinations of modems to determine which one is not functioning properly. A pair of operable modems connect and complete sending data in both directions. An operable modem and an inoperable modem do not connect with each other.

To perform the modem test procedure, enter the test modem back-to-back first - slot / port second-slot / port command, as follows:

Step 1 Perform a back-to-back modem test between two normal functioning modems. This example shows a successful connection between modem 1/1 and modem 1/0, which verifies normal operating conditions between these two modems:

After you enter the test modem back-to-back command, you must define the number of packets sent between modems at the Repetitions prompt. The ideal range of packets to send and receive is from 1 to 100. The default is 1 packet that is 10 bytes large. The response message (for example, “success/packets = 20/20”) tells you how many packets were sent in both directions compared to the total number of packets attempted to be sent in both directions. Because the software reports the packet total in both directions, the reported numbers are two times the number you originally specify.

When a known good modem is tested against a known bad modem, the back-to-back modem test fails. In the following example, modem 1/3 is suspected or proven to be inoperable or bad:

Step 2 You would need to manually mark modem 1/3 as an inoperable or bad modem. You mark the bad modem by determining which line number corresponds with the modem. Use the show modem 1/3 EXEC command to verify that TTY line number 4 (shown as TTY4) is used for modem 1/3:

Step 3 Enter line configuration mode and manually remove modem 1/3 from dial services by entering the modem bad command on line 4:

Step 4 Enter the show modem EXEC command or the show modem slot / port command to display the bad modem status.

Bad modems are marked with the letter B in the Mdm column of the show modem command display output.

Malfunctioning modems are also marked as Bad in the Status column of the show modem slot / port command display output, as the following example shows:

Clearing a Direct Connect Session on a Microcom Modem

The examples in this section are for Microcom modems.

The following example shows how to execute the modem at-mode command from a Telnet session:

The following example shows how to execute the clear modem at-mode command from a second Telnet session while the first Telnet session is connected to the modem:

The following output is displayed in the first Telnet session after the modem is cleared by the second Telnet session:

Displaying Local Disconnect Reasons

To find out why a modem ended its connection or why a modem is not operating at peak performance, use the show modem call-stats [ slot ] EXEC command.

Disconnect reasons are described using four hexadecimal digits. The three lower-order digits can be used to identify the disconnect reason. The high-order digit generally indicates the type of disconnect reason or the time at which the disconnect occurred. For detailed information on the meaning of hexadecimal values for MICA modem disconnects, refer to the TAC Tech Notes document, MICA Modem States and Disconnect Reasons, at the following URL: http://www.cisco.com/warp/public/76/mica-states-drs.html

For detailed information on the meaning of hexadecimal values for NextPort modem disconnects, refer to the TAC Tech Notes document, Interpreting NextPort Disconnect Reason Codes, at the following URL: http://www.cisco.com/warp/public/471/np_disc_code.html.

Local disconnect reasons are listed across the top of the screen display (for example, wdogTimr, compress, retrain, inacTout, linkFail, moduFail, mnpProto, and lapmProt). In the body of the screen display, the number of times each modem disconnected is displayed (see the # column). For a particular disconnect reason, the % column indicates the percent that a modem was logged for the specified disconnect reason with respect to the entire modem pool for that given reason. For example, out of all the times the rmtLink error occurred on all the modems in the system, the rmtLink error occurred 10 percent of the time on modem 0/22.

Malfunctioning modems are detected by an unusually high number of disconnect counters for a particular disconnect reason. For example, if modem 1/0 had a high number of compression errors compared to the remaining modems in system, modem 1/0 would likely be the inoperable modem.

To reset the counters displayed by the show modem call-stats command, enter the clear modem counters command.

Note For a complete description of each error field displayed by the commands on this page, refer to the Cisco IOS Dial Technologies Command Reference. Remote disconnect reasons are not described by the show modem command output.

The following example displays output for the show modem call-stats command. Because of the screen size limitation of most terminal screen displays, not all possible disconnect reasons are displayed at one time. Only the top eight most frequently experienced disconnect reasons are displayed at one time.

Removing Inoperable Modems

To manually remove inoperable modems from dialup services, use the following commands in line configuration mode:

If you use the modem bad command to remove an idle modem from dial services and mark it as inoperable, the letter B is used to identify the modem as bad. The letter B appears in the Status column in the output of show modem slot / port command and in the far left column in the output of the show modem command. Use the no modem bad command to unmark a modem as B and restore it for dialup connection services. If the letter B appears next to a modem number, it means the modem was removed from service with the modem shutdown command.

Note Only idle modems can be marked “bad” by the modem bad command. If you want to mark a modem bad that is actively supporting a call, first enter the modem shutdown command, then enter the modem bad command.

Use the modem hold-reset command if a router is experiencing extreme modem behavior (for example, if the modem is uncontrollably dialing in to the network). This command prevents the modem from establishing software relationships such as those created by the test modem back-to-back command. The modem is unusable while the modem hold-reset command is configured. The modem hold-reset command also resets a modem that is frozen in a suspended state. Disable the suspended modem with the modem hold-reset command, and then restart hardware initialization with the no modem hold-reset command.

The following example disables a suspended modem and resets its hardware initialization:

The following example gracefully disables the modem associated with line 1 from dialing and answering calls. The modem is disabled only after all active calls on the modem are dropped.

The following example abruptly shuts down the modem associated with line 2. All active calls on the modem are dropped immediately.

In the following example, the modem using TTY line 3 is actively supporting a call (as indicated by the asterisk). However, we want to mark the modem bad because it has poor connection performance. First, abruptly shut down the modem and drop the call with the modem shutdown command, and then enter the modem bad command to take the modem out of service.

For more information about modem recovery procedures, refer to TAC Tech Notes Configuring MICA Modem Recovery at http://www.cisco.com/warp/public/76/modem-recovery.html and Configuring NextPort SPE Recovery at http://www.cisco.com/warp/public/76/spe-recovery.html.

Busying Out a Modem Card

To busy out a modem card in a Cisco access server, use the following commands beginning in global configuration mode:

The modem busyout command disables the modem associated with a specified line from dialing and answering calls. The modem busyout command can busy out and eventually terminate all 72 ports on the Cisco AS5800 modem card.

Monitoring Resources on Cisco High-End Access Servers

The following tasks enable you to monitor the network access server (NAS) health conditions at the DS0 level, PRI bearer channel level, and modem level. Performing these tasks will benefit network operation with improved visibility into the line status for the NAS for comprehensive health monitoring and notification capability, and improved troubleshooting and diagnostics for large-scale dial networks.

Perform the following tasks to monitor resource availability on the Cisco high-end access servers:

• Enabling DS0 Busyout Traps—DS0 busyout traps are generated when there is a request to busy out a DS0, when there is a request to take a DS0 out of busyout mode, or when busyout completes and the DS0 is out-of-service. DS0 busyout traps are generated at the DS0 level for both CAS and ISDN configured lines. This feature is enabled and disabled through use of the CLI and MIBs. DS0 busyout traps are disabled by default and are supported on Cisco AS5300, Cisco AS5400, and Cisco AS5800 universal access servers.
• Enabling ISDN PRI Requested Channel Not Available Traps—ISDN PRI channel not available traps are generated when a requested DS0 channel is not available, or when there is no modem available to take the incoming call. This feature is available only for ISDN PRI interfaces. This feature is enabled and disabled through use of CLI for ISDN traps and the CISCO-ISDN-MIB. ISDN PRI channel not available traps are disabled by default and are supported on the Cisco AS5300, Cisco AS5400, and Cisco AS5800.
• Enabling Modem Health Traps—Modem health traps are generated when a modem port is bad, disabled, reflashed, or shut down, or when there is a request to busy out the modem. This feature is enabled and disabled through use of CLI and the CISCO-MODEM-MGMT-MIB. Modem health traps are disabled by default and are supported on the Cisco AS5300, Cisco AS5400, and Cisco AS5800.
• Enabling DS1 Loopback Traps—DS1 loopback traps are generated when a DS1 line goes into loopback mode. This feature is enabled and disabled by CLI and the CISCO-POP-MGMT-MIB. DS1 loopback traps are disabled by default and are supported on the Cisco AS5300 and Cisco AS5400 only.

The CISCO-POP-MGMT-MIB supplies the DS0 busyout traps and the DS1 loopback traps. The CISCO-MODEM-MGMT-MIB supplies additional modem health traps when the modem port becomes non-functional. The CISCO-ISDN-MIB supplies additional traps for ISDN PRI channel not available.

To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.

See the sections “Verifying Enabled Traps” and “Troubleshooting the Traps” to verify and troubleshoot configuration. The section “NAS Health Monitoring Example” provides output of a configuration with the NAS health monitoring features enabled.

Enabling DS0 Busyout Traps

Before you enable DS0 busyout traps, the SNMP manager must already have been installed on your workstation, and the SNMP agent must be configured on the NAS by entering the snmp-server community and snmp-server host commands. Refer to the Cisco IOS Configuration Fundamentals Configuration Guide for more information on these commands.

To generate DS0 busyout traps, use the following command in global configuration mode:

Enabling ISDN PRI Requested Channel Not Available Traps

To generate ISDN PRI requested channel not available traps, use the following command in global configuration mode:

Enabling Modem Health Traps

To generate modem health traps, use the following command in global configuration mode:

Enabling DS1 Loopback Traps

To generate DS1 loopback traps, use the following command in global configuration mode:

Verifying Enabled Traps

To verify that the traps are enabled, use the show run command. The following output indicates that all the traps are enabled:

Additionally, you can use the show controllers command with the timeslots keyword to display details about the channel state. This feature shows whether the DS0 channels of a particular controller are in idle, in-service, maintenance, or busyout state. This enhancement applies to both CAS and ISDN PRI interfaces and is supported on the Cisco AS5300 and Cisco AS5400 only.

Troubleshooting the Traps

To troubleshoot the traps, turn on the debug switch for SNMP packets by entering the following command in privileged EXEC mode:

Check the resulting output to see that the SNMP trap information packet is being sent. The output will vary based on the kind of packet sent or received:

You can also use trap monitoring and logging tools like snmptrapd, with debugging flags turned on, to monitor output.

NAS Health Monitoring Example

The following is sample configuration output showing all NAS health monitoring traps turned on:

NextPort Modem Log Example

The following is partial sample output for the Cisco AS5400 with the NextPort Distributed forwarding Card (DFC). This example shows the port history event log for slot 5, port 47:

Modem Performance Summary Example

You can display a high level summary of the performance of a modem with the show modem summary command:

Modem AT-Mode Example

The following example shows that modem 1/1 has one open AT directly connected session:

Connection Speed Performance Verification Example

Making sure that your modems are connecting at the correct connection speeds is an important aspect of managing modems. The show modem connect-speeds and show modem commands provide performance information that allow you to investigate possible inoperable or corrupt modems or T1/E1 lines. For example, suppose you have an access server that is fully populated with V.34 modems. If you notice that modem 1/0 is getting V.34 connections only 50 percent of the time, whereas all the other modems are getting V.34 connections 80 percent of the time, then modem 1/0 is probably malfunctioning. If you are reading low connection speeds across all the modems, you may have a faulty channelized T1 or ISDN PRI line connection.

To display connection speed information for all modems that are running in your system, use the show modem connect-speeds max-speed EXEC command. Because most terminal screens are not wide enough to display the entire range of connection speeds at one time (for example, 75 to 56,000 bps), the max-speed argument is used. This argument specifies the contents of a shifting baud-rate window, which provides you with a snapshot of the modem connection speeds for your system. Replace the max-speed argument with the maximum connect speed that you want to display. You can specify from 12,000 to 56,000 bps. If you are interested in viewing a snapshot of lower baud rates, specify a lower connection speed. If you are interested in displaying a snapshot of higher rates, specify a higher connection speed.

The following example displays connection speed information for modems running up to 33,600 bps:

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