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This chapter describes features that either depend on special signalling services offered by an ISDN network service provider or overcome an inability to deliver certain signals. It describes these features in the following main sections:
For an overview of ISDN PRI, see the section "ISDN Service" in the "Interfaces, Controllers, and Lines Used for Dial Access Overview" chapter, and the section "ISDN Overview" in the "Setting Up Basic ISDN Service" chapter.
For a complete description of the ISDN signalling commands in this chapter, see the Cisco IOS Dial Services Command Reference publication. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
Perform the tasks in the following sections to configure special signalling features of ISDN; all tasks are optional:
See the section "ISDN Special Signalling Configuration Examples" at the end of this chapter for examples of these signalling features. See the "Troubleshooting ISDN Special Signalling" section later in this chapter for help in troubleshooting ISDN signalling features.
The ISDN AOC feature also supports, for the AOC-D service, an optional configurable short-hold mode that provides a dynamic idle timeout by measuring the call charging period, based on the frequency of the AOC-D or the AOC-E message from the network. The short-hold mode allows users to track call costs and to control and possibly reduce tariff charges. The short-hold mode idle time will do the following:
Incoming calls are disconnected using the static dialer idle timeout value.
The AOC-D and AOC-E messages are part of the Facility Information Element (IE) message. Its contents can be verified with the debug q931 command. Call accounting information from AOC-D and AOC-E messages is stored in Simple Network Management Protocol (SNMP) MIB objects.
ISDN AOC is provided for ISDN PRI NET5 and ISDN BRI NET3 switch types only. AOC information at call setup is not supported.
No configuration is required to enable ISDN AOC. However, you can configure the optional short-hold minimum idle timeout period for outgoing calls; the default minimum idle timeout is
120 seconds. If the short-hold option is not configured, the router default is to use the static dialer idle timeout. If the short-hold idle timeout has been configured but no charging information is available from the network, the static dialer idle timeout applies.
To configure an ISDN interface and provide the AOC short-hold mode option on an ISDN interface, perform the following steps:
Step 2 Configure dialer profiles or legacy dial-on-demand routing (DDR) for outgoing calls, as described in the chapters in the "Dial-on-Demand Routing" part of this publication, making sure to do the following:
Step 3 Configure each specified dialer map class, providing a dialer idle timeout, or ISDN short-hold timeout, or both for outgoing calls, as described in this chapter.
| Command | Purpose | |
|---|---|---|
Step 1 | map-class dialer classname | Specifies the dialer map class. |
Step 2 | dialer idle-timeout seconds | (Optional) Specifies a static idle timeout for the map class to override the static line-idle timeout configured on the BRI interface. |
Step 3 | dialer isdn short-hold seconds | Specifies a dialer ISDN short-hold timeout for the map class. |
To monitor ISDN AOC call information, use the following command in EXEC mode:
| Command | Purpose |
|---|---|
show isdn {active | history | memory | service | status | timers} |
ISDN Non-Facility Associated Signalling (NFAS) allows a single D channel to control multiple PRI interfaces. A backup D channel can also be configured for use when the primary NFAS D channel fails.
Use of a single D channel to control multiple PRI interfaces can free one B channel on each interface to carry other traffic.
Any hard failure causes a switchover to the backup D channel and currently connected calls remain connected.
Once the channelized T1controllers are configured for ISDN PRI, only the NFAS primary D channel must be configured; its configuration is distributed to all the members of the associated NFAS group.
NFAS is only supported with a channelized T1 controller and, as a result, must be ISDN PRI capable.
The channelized T1 controllers on the router must also be configured for ISDN, as described in the section "ISDN PRI Configuration Task List" in the chapter "Configuring ISDN PRI and Other Signalling on E1 and T1 Lines" in this publication.
The router must connect to either an AT&T 4ESS, Northern Telecom DMS-100 or DMS-250, or National ISDN switch type.
Table 20 shows the applicable ISDN switch types and supported NFAS types.
| Switch Type | NFAS Type |
|---|---|
Lucent 4ESS | Custom NFAS |
Northern Telecom DMS-250 | Custom NFAS |
Northern Telecom DMS-100 | Custom NFAS |
Lucent 5ESS | Custom (Does not support NFAS) |
Lucent 5ESS | NI NFAS |
AGCS GTD5 | NI NFAS |
Other Switch Types | NI NFAS |
 |
Note On the Northern Telecom DMS-100 switch, when a single D channel is shared, multiple PRI interfaces may be configured in a single trunk group. The additional use of alternate route indexing, which is a feature of the DMS-100 switch, provides a rotary from one trunk group to another. This feature enables the capability of building large trunk groups in a public switched network. |
To configure NFAS on channelized T1 controllers configured for ISDN, perform the tasks in the following section: Configuring NFAS on PRI Groups (required).
You can also disable a channel or interface, if necessary, and monitor NFAS groups and ISDN service. To do so, perform the tasks in the following sections:
See the section "NFAS Primary and Backup D Channels" later in this chapter for ISDN, NFAS, and DDR configuration examples.
This section documents tasks used to configure NFAS with D channel backup. When configuring NFAS, you use an extended version of the ISDN pri-group command to specify the following values for the associated channelized T1 controllers configured for ISDN:
To configure ISDN NFAS, use the following commands in controller configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | pri-group timeslots 1-24 nfas_d primary nfas_interface number nfas_group number | On one channelized T1 controller, configures the NFAS primary |
Step 2 | pri-group timeslots 1-24 nfas_d backup nfas_interface number nfas_group number | On a different channelized T1 controller, configures the NFAS backup D channel to be used if the primary D channel fails. |
Step 3 | pri-group timeslots 1-24 nfas_d none nfas_interface number nfas_group number | (Optional) On other channelized T1 controllers, configures a 24-B-channel interface, if desired. |
For an example of configuring three T1 controllers for the NFAS primary D channel, the backup D channel, and 24 B channels, along with the DDR configuration for the PRI interface, see the section "NFAS Primary and Backup D Channels" at the end of this chapter.
When a backup NFAS D channel is configured and the primary NFAS D channel fails, rollover to the backup D channel is automatic and all connected calls stay connected.
If the primary NFAS D channel recovers, the backup NFAS D channel remains active and does not switch over again unless the backup NFAS D channel fails.
You can disable a specified channel or an entire PRI interface, thus taking it out of service or placing it into one of the other states that is passed in to the switch. To disable a specific channel or PRI interface, use one of the following commands in interface configuration mode:
| Command | Purpose |
isdn service dsl number b_channel number state state-value | Takes an individual B channel out of service or sets it to a different state. |
isdn service dsl number b_channel 0 state state-value | Sets the entire PRI to the specified state. |
The supported state-values are as follows:
To monitor NFAS groups, use the following command in EXEC mode:
| Command | Purpose |
|---|---|
show isdn nfas group number | Displays information about members of an NFAS group. |
To display information about ISDN channel service states, use the following command in EXEC mode:
| Command | Purpose |
|---|---|
show isdn service | Displays information about ISDN channels and the service states. |
Configuring BRI interfaces for semipermanent connection requires only that you use a keyword that indicates semipermanent connections when you are setting up network addressing as described in the previous section of this chapter.
To configure a BRI for semipermanent connections, follow this procedure:
Step 2 Configure DDR on a selected interface, as described in the "Dial-on-Demand Routing" part of this publication.
To begin DDR network addressing, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
dialer map protocol next-hop-address name hostname spc [speed 56 | 64] [broadcast] dial-string[:isdn-subaddress] | Defines the remote recipient's protocol address, host name, and dialing string; indicate semipermanent connections; optionally, provide the ISDN subaddress; set the dialer speed to 56 or 64 kbps, as needed. |
To configure the BRI to use the ISDN connection as a leased-line service, use the following commands in global configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | isdn switch-type switch-type | Configures the BRI switch type, as specified by the local service provider. |
Step 2 | isdn leased-line bri number 128 | Specifies the BRI interface number. |
To disable leased-line service if you no longer want to support it on a specified ISDN BRI, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
no isdn leased-line bri number | Removes leased line configuration from a specified ISDN BRI interface. |
|
Note This feature is not supported on the Cisco 2500 series router because its BRI hardware does not support channel aggregation. |
| Command | Purpose | |
|---|---|---|
Step 1 | isdn switch-type switch-type | Selects the service provider switch type. |
Step 2 | isdn leased-line bri number 128 | Configures a specified BRI for access over leased lines. |
To complete the configuration of the interface, see the chapter "Configure a Synchronous Serial Ports" in this publication.
To remove the leased-line service configuration from a specified ISDN BRI, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
no isdn leased-line bri number | Removes leased-line configuration from a specified ISDN BRI interface. |
You can enable a serial or ISDN interface to accept calls and dynamically change the encapsulation in effect on the interface when the remote device does not signal the call type. For example, if an ISDN call does not identify the call type in the lower-layer compatibility fields and is using an encapsulation that is different from the one configured on the interface, the interface can change its encapsulation type dynamically.
This feature enables interoperation with ISDN terminal adapters that use V.120 encapsulation but do not signal V.120 in the call setup message. An ISDN interface that by default answers a call as synchronous serial with PPP encapsulation can change its encapsulation and answer such calls.
Automatic detection is attempted for the first 10 seconds after the link is established or the first 5 packets exchanged over the link, whichever is first.
To enable automatic detection of encapsulation type, use the following command in interface configuration mode:
| Command | Purpose |
|---|---|
autodetect encapsulation encapsulation-type | Enables automatic detection of encapsulation type on the specified interface. |
You can specify one or more encapsulations to detect. Cisco IOS software currently supports automatic detection of PPP and V.120 encapsulations.
Historically, Combinet devices supported only the Combinet Proprietary Protocol (CPP) for negotiating connections over ISDN B channels. To enable Cisco routers to communicate with those Combinet bridges, the Cisco IOS supports a the CPP encapsulation type.
To enable routers to communicate over ISDN interfaces with Combinet bridges that support only CPP, use the following commands in interface configuration mode:
| Command | Purpose | |
|---|---|---|
Step 1 | e ncapsulation cpp | Specifies CPP encapsulation. |
Step 2 | cpp callback accept | Enables CPP callback acceptance. |
Step 3 | cpp authentication | Enables CPP authentication. |
Most Combinet devices support PPP. Cisco routers can communicate over ISDN with these devices by using PPP encapsulation, which supports both routing and fast switching.
Cisco 700 and 800 series routers and bridges (formerly Combinet devices) support only IP, Internet Protocol Exchange (IPX), and bridging. For AppleTalk, Cisco routers automatically perform half-bridging with Combinet devices. For more information about half-bridging, see the section "Configuring PPP Half-Bridging" in the chapter "Configuring Media-Independent PPP and Multilink PPP" later in this publication.
Cisco routers can also half-bridge IP and IPX with Combinet devices that support only CPP. To configure this feature, you only need to set up the addressing with the ISDN interface as part of the remote subnet; no additional commands are required.
To troubleshoot ISDN, use any of the following commands in EXEC mode:
| Command | Purpose |
|---|---|
debug dialer | Displays the values of timers. |
debug isdn q921 [interface bri number] debug isdn q921 interface serial slot/controller-number:23 | Displays link layer information for all interfaces or, optionally, for a single BRI interface. |
debug isdn q931 [interface bri number]
| Displays the content of call control messages and information elements, in particular the Facility IE message for all interfaces or, optionally, for a single BRI interface. |
This section provides the following configuration examples:
This section provides the following ISDN AOC configuration examples:
This example shows ISDN PRI configured on an E1 controller. Legacy DDR is configured on the ISDN D channel (serial interface 0:15) and propagates to all ISDN B channels. A static dialer idle-timeout is configured for all incoming calls on the B channels, but the map classes are configured independently of it. Map classes Kappa and Beta use AOC charging unit duration to calculate the timeout for the call. A short-hold idle timer is set so that if the line is idle for 10 or more seconds, the call is disconnected when the current charging period ends. Map class Iota uses a static idle timeout.
version 11.2 service timestamps debug datetime msec service timestamps log datetime msec ! hostname A ! username c2503isdn password 7 1511021F0725 username B password 7 110A1016141D29 username C password 7 1511021F072508 isdn switch-type primary-net5 ! controller E1 0 pri-group timeslots 1-31 ! interface Serial 0:15 ip address 10.0.0.35 255.0.0.0 encapsulation ppp dialer idle-timeout 150 dialer map ip 10.0.0.33 name c2503isdn class Iota 06966600050 dialer map ip 10.0.0.40 name B class Beta 778578 dialer map ip 10.0.0.45 name C class Kappa 778579 dialer-group 1 ppp authentication chap ! map-class dialer Kappa dialer idle-timeout 300 dialer isdn short-hold 120 ! map-class dialer Iota dialer idle-timeout 300 ! map-class dialer Beta dialer idle-timeout 300 dialer isdn short-hold 90 ! dialer-list 1 protocol ip permit
This example shows ISDN BRI configured as a member of two dialer pools for dialer profiles.
version 11.2 service timestamps debug datetime msec service timestamps log datetime msec ! hostname delorean ! username spanky password 7 0705344245 username delorean password 7 1511021F0725 isdn switch-type basic-net3 ! interface BRI0 description Connected to NTT 81012345678901 no ip address dialer pool-member 1 max-link 1 dialer pool-member 2 max-link encapsulation ppp no fair-queue ! interface Dialer1 ip address 7.1.1.8 255.255.255.0 encapsulation ppp dialer remote-name spanky dialer string 81012345678902 class Omega dialer pool 1 dialer-group 1 ppp authentication chap ! interface Dialer2 ip address 8.1.1.8 255.255.255.0 encapsulation ppp dialer remote-name dmsisdn dialer string 81012345678902 class Omega dialer string 14153909503 class Gamma dialer pool 2 dialer-group 1 ppp authentication chap ! map-class dialer Omega dialer idle-timeout 60 dialer isdn short-hold 150 ! map-class dialer Gamma dialer isdn short-hold 60 ! dialer-list 1 protocol ip permit
This section provides the following configuration examples:
The following example configures ISDN PRI and NFAS on three T1 controllers of a Cisco 7500 series router. The NFAS primary D channel is configured on the 1/0 controller, and the NFAS backup D channel is configured on the 1/1 controller. No NFAS D channel is configured on the 2/0 controller; it is configured for 24 B channels. Once the NFAS primary D channel is configured, it is the only interface you see and need to configure; DDR configuration for the primary D channel-which is distributed to all B channels-is also included in this example.
isdn switch-type primary-4ess ! ! NFAS primary D channel on the channelized T1 controller in 1/0. controller t1 1/0 framing esf linecode b8zs pri-group timeslots 1-24 nfas_d primary nfas_interface 0 nfas_group 1 . ! ! NFAS backup D channel on the channelized T1 controller in 1/1. controller t1 1/1 framing esf linecode b8zs pri-group timeslots 1-24 nfas_d backup nfas_interface 1 nfas_group 1 . ! ! NFAS 24 B channels on the channelized T1 controller in 2/0 controller t1 2/0 framing esf linecode b8zs pri-group timeslots 1-24 nfas_d none nfas_interface 2 nfas_group 1 ! ! NFAS primary D channel interface configuration for PPP and DDR. This ! configuration is distributed to all the B channels in NFAS group 1 on the ! three channelized T1 controllers. ! interface Serial 1/0:23 ip address 1.1.1.2 255.255.255.0 no ip mroute-cache encapsulation ppp dialer map ip 1.1.1.1 name flyboy 567898 dialer map ip 1.1.1.3 name flyboy 101112345678 dialer map ip 1.1.1.4 name flyboy 01112345678 dialer-group 1 no fair-queue no cdp enable ppp authentication chap
The following example puts the entire PRI interface back in service after it previously had been taken out of service:
isdn service dsl 0 b-channel 0 state 0
The following example configures the BRI 0 interface for leased-line access at 128 kbps. Because of the leased-line-not dialed-environment, configuration of ISDN called and calling numbers are not needed and not used. The BRI 0 interface is henceforth treated as a synchronous serial interface, with the default HDLC encapsulation.
isdn leased-line bri 0 128
The following example configures the BRI 0 interface for PPP encapsulation:
interface bri 0 ip address 1.1.1.2 255.255.255.0 encapsulation ppp bandwidth 128
Posted: Fri Aug 25 13:51:28 PDT 2000
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