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Use the information in this chapter to configure serial interfaces.
For information on configuring an Asynchronous Transfer Mode (ATM) interface, see the "Configuring ATM Access over a Serial Interface" chapter in the Wide-Area Networking Configuration Guide.
See also the section "Invoke ATM over a Serial Line" in the section "Configure a Synchronous Serial Interface" in this chapter.
For hardware technical descriptions and information about installing interfaces, refer to the hardware installation and maintenance publication for your product. For a complete description of serial interface commands used in this chapter, refer to the "Interface Commands" chapter of the Configuration Fundamentals Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
These sections are included in this chapter:
For examples of conguration tasks shown in this chapter, see "Serial Interface Configuration Examples" at the end of this chapter.
The HSSI Interface Processor (HIP) provides a single HSSI network interface. The network interface resides on a modular interface processor that provides a direct connection between the high-speed CiscoBus and an external network.
Perform the tasks in the following sections to configure a HSSI interface. The first task is required; the remaining tasks are optional.
To specify a HSSI and enter interface configuration mode, perform one of the following tasks in global configuration mode:
| Task | Command |
|---|---|
Begin interface configuration. | interface hssi number |
Begin interface configuration for the Cisco 7500 series. | interface hssi slot/port |
The HSSI supports the serial encapsulation methods, except for X.25-based encapsulations. The default method is HDLC. You can define the encapsulation method by performing the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure HSSI encapsulation. | encapsulation {atm-dxi | hdlc | frame-relay | ppp | sdlc-primary | sdlc-secondary | smds | stun} |
For information about PPP, see the "Configure SLIP and PPP" chapter of the Access Services Configuration Guide and the "Configure PPP for Wide-Area Networking" chapter of the Wide-Area Networking Configuration Guide.
If you have an ATM DSU, you can invoke ATM over a HSSI line. You do so by mapping an ATM virtual path identifier (VPI) and virtual channel identifier (VCI) to a DXI frame address. ATM-DXI encapsulation defines a data exchange interface that allows a DTE (such as a router) and a DCE (such as an ATM DSU) to cooperate to provide a User-Network Interface (UNI) for ATM networks.
To invoke ATM over a serial line, perform the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Step 1 Specify the encapsulation method. | |
Step 2 Map a given VPI and VCI to a DXI frame address. |
You can also configure the dxi map command on a serial interface.
To configure an ATM interface using an AIP card, see the "Configuring ATM" chapter in the Wide-Area Networking Configuration Guide.
You can convert the HSSI interface into a 45-MHz clock master by performing the following task in interface configuration mode:
| Task | Command |
|---|---|
Convert the HSSI interface into a 45-MHz clock master. |
Synchronous serial interfaces are supported on various serial network interface cards or systems. These interfaces support full-duplex operation at T1 (1.544 Mbps) and E1 (2.048 Mbps) speeds. Refer to the Cisco Product Catalog for specific information regarding platform and hardware compatibility.
Perform the tasks in the following sections to configure a synchronous serial interface. The first task is required; the remaining tasks are optional.
See the "Serial Interface Configuration Examples" section at the end of this chapter for examples of configuration tasks described in this chapter.
To specify a synchronous serial interface and enter interface configuration mode, perform one of the following tasks in global configuration mode:
| Task | Command |
|---|---|
Begin interface configuration. | interface serial number |
Begin interface configuration for the Cisco 7205 or Cisco 7200 series. | interface serial slot/port |
Begin interface configuration for the Cisco 7500 series. | interface serial slot/port-adapter/port |
Begin interface configuration for a channelized T1 or E1 interface. | interface serial slot/port:channel-group (Cisco 7000 series) |
By default, synchronous serial lines use the High-Level Data Link Control (HDLC) serial encapsulation method, which provides the synchronous framing and error detection functions of HDLC without windowing or retransmission. The synchronous serial interfaces support the following serial encapsulation methods:
You can define the encapsulation method by performing the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure synchronous serial encapsulation. | encapsulation {atm-dxi | hdlc | frame-relay | ppp | sdlc-primary | sdlc-secondary | smds | stun | x25} |
Encapsulation methods are set according to the type of protocol or application you configure in the Cisco IOS software. ATM-DXI is described in this chapter in the section "Invoke ATM over a Serial Line." PPP is described in the "Configure PPP for Wide-Area Networking" chapter. The remaining encapsulation methods are defined in their respective books and chapters describing the protocols or applications. Serial encapsulation methods are also discussed in the Configuration Fundamentals Command Reference in the chapter "Interface Commands" under the encapsulation command.
By default, synchronous interfaces operate in full-duplex mode. To configure an SDLC interface for half-duplex mode, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure an SDLC interface for half-duplex mode. |
BSC is a half-duplex protocol. Each block of transmission is acknowledged explicitly. To avoid the problem associated with simultaneous transmission, there is an implicit role of primary and secondary station. The primary resends the last block if there is no response from the secondary within the period of block receive timeout.
To configure the serial interface for full-duplex mode, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify that the interface can run BSC using switched RTS signals. | full-duplex |
The CT3IP is a fixed-configuration interface processor based on the second-generation Versatile Interface Processor (VIP2). It is supported on the Cisco 7500 series routers. The CT3IP has four T1 connections via DB-15 connectors and one DS3 connection via BNC connectors. Each DS3 interface can provide up to 28 T1 channels (a single T3 group). Each channel is presented to the system as a serial interface that can be configured individually. The CT3IP can transmit and receive data bidirectionally at the T1 rate of 1.536 Mbps. The four T1 connections use 100-ohm twisted-pair serial cables to external channel service units (CSUs) or to a MultiChannel Interface Processor (MIP) on the same router or on another router. For wide-area networking, the CT3IP can function as a concentrator for a remote site.
The first three T1 channels of the CT3IP can be broken out to the three DSUP-15 connectors on the CPT3IP so the T1 can be further demultiplexed by the MIP on the same router or on another router, or by other multiplexing equipment. When connecting to the MIP, you configure a channelized T1 as described in the "Configure External T1 Channels" section. This is referred to as an external T1 channel.
The CT3IP supports RFC 1406 and RFC 1407 (CISCO-RFC-1407-CAPABILITY.my). For information Cisco MIBs, refer to the current Cisco IOS release note for the location of the Management Information Base (MIB) online reference.
For RFC 1406, Cisco supports all tables except the "Frac" table. For RFC 1407, Cisco supports all tables except the "FarEnd" tables.
The CT3IP supports the following WAN protocols:
The CT3IP meets ANSI T1.102-1987 and BELCORE TR-TSY-000499 specifications for T3 and meets ANSI 62411 and BELCORE TR499 specifications for T1. The CT3IP provides internal CSU functionality and includes reporting performance data statistics, transmit and receive statistics, and error statistics. The CT3IP supports RFC 1406 (T1 MIB) and RFC 1407 (T3 MIB).
External T1 channels do not provide CSU functionality and must connect to an external CSU.
The CT3IP supports RFC 1406 (T1 MIB) and RFC 1407 (T3 MIB).
Perform the tasks in the following sections to configure the CT3IP (all tasks are optional except for the second task):
After you configure the T1 channels on the CT3IP, you can continue configuring it as you would a normal serial interface. All serial interface commands might not be applicable to the T1 channel. For more information, see the "Configure a Synchronous Serial Interface" section earlier in this chapter.
For CT3IP configuration examples, see the "Channelized T3 Interface Processor Configuration Examples" section, later in this chapter.
If you do not modify the configuration of the CT3IP, the configuration defaults shown in Table 11 are used.
| Attribute | Default Value |
|---|---|
Framing | auto-detect |
Cable length | 224 feet |
Clock source | internal |
| Task | Command |
|---|---|
Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Change the framing format. | framing {c-bit | m23 | auto-detect} |
Change the cable length (values are 0 to 450 feet). | cablelength feet |
Change the clock source used by the T3 controller. | clock source {internal | line} |
You must configure the timeslots used by each T1 channel on the CT3IP. Optionally, you can specify the speed, framing format, and clock source used by each T1 channel. If you do not specify the speed, framing format, and clock source used by each T1 channel, the configuration defaults shown in Table 12 are used.
| Attribute | Default Value |
|---|---|
Speed | 64 kbps |
Framing | esf |
Clock source | internal |
Linecode | b8zs |
T1 yellow alarm | detection and generation |
To specify the timeslots used by each T1 channel, complete the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
Step 1 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 2 Configure the timeslots (values are 1 to 24) for the T1 channel (values are 1 to 28) and optionally specify the speed for each T1 channel. | t1 channel timeslot range [speed {56 | 64}] |
| Task | Command |
|---|---|
Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Change the framing format used by the T1 channel (values are 1 to 28). | t1 channel framing {esf | sf} |
Change the clock source used by the T1 channel (values are 1 to 28). | t1 channel clock source {internal | line} |
Change the line coding used by the T1 channel (values are 1 to 28). | t1 channel linecode {ami | b8zs} |
Disable detection or generation of a yellow alarm on the T1 channel (values are 1 to 28). | no t1 channel yellow {detection | generation} |
After you configure the T1 channels on the CT3IP, you can continue configuring it as you would a normal serial interface. All serial interface commands might not be applicable to the T1 channel. For more information, refer to the "Configure a Synchronous Serial Interface" in this chapter.
To enter interface configuration mode and configure the serial interface that corresponds to a T1 channel, perform the following task in global configuration mode:
| Task | Command |
|---|---|
Define the serial interface for a T1 channel (values are 1 to 28) and enter interface configuration mode. | interface serial slot/port-adapter/port:t1-channel |
In addition to the commands in the "Configure a Synchronous Serial Interface" section, the invert data interface command can be used to configure the T1 channels on the CT3IP. If the T1 channel on the CT3IP is using AMI line coding, you must invert the data. For information on the invert data interface command, refer to "Invert the Data" later in this chapter. For more information, see the t1 linecode controller command.
To configure a T1 channel as an external port, complete the following tasks beginning in EXEC mode:
| Task | Command |
|---|---|
Step 1 Determine if the external device connected to the external T1 port is configured and cabled correctly by locating the line | show controller t3 slot/port-adapter/port |
Step 2 Enter configuration mode. | configure terminal |
Step 3 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 4 Configure the T1 channel (values are 1, 2, and 3) as an external port and optionally specify the cable length and line code. The default cable length is 133 feet, and the default line code is b8zs. | t1 external channel [cablelength feet] [linecode {ami | b8zs}] |
After you configure the external T1 channel, you can continue configuring it as a channelized T1 from the MIP. All channelized T1 commands might not be applicable to the T1 interface. To define the T1 controller and enter controller configuration mode, perform the following task in global configuration mode:
| Task | Command |
|---|---|
Select the MIP and enter controller configuration mode. | controller t1 slot/port |
After you configure the channelized T1 on the MIP, you can continue configuring it as you would a normal serial interface. All serial interface commands might not be applicable to the T1 interface. To enter interface configuration mode and configure the serial interface that corresponds to a T1 channel group, perform the following task beginning in global configuration mode:
| Task | Command |
|---|---|
Define the serial interface for a T1 channel on the MIP (values are 1 to 28) and enter interface configuration mode. | interface serial slot/port:t1-channel |
For more information, refer to the "Configure Channelized T1" section and the "Configure a Synchronous Serial Interface" section in the "Configuring Interfaces" chapter of this guide.
For an example of configuring an external T1 channel, see the "Channelized T3 Interface Processor Configuration Examples" section later in this chapter.
You can use the following methods to troubleshoot the CT3IP using Cisco IOS software:
The T1 test port is also available as an external port. For more information on configuring an external port, see the previous section, "Configure External T1 Channels."
To enable a T1 channel as a test port, complete the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
Step 1 Determine if the external device connected to the external T1 port is configured and cabled correctly by locating the line | show controller t3 slot/port-adapter/port |
Step 2 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 3 Enable the T1 channel (values are 1 to 28) as a test port and optionally specify the cable length and line code. The default cable length is 133 feet, and the default line code is b8zs. | t1 test channel [cablelength feet] [linecode {ami | b8zs}] |
To disable a T1 channel as a test port, complete the following tasks beginning in global configuration mode:
| Task | Command |
|---|---|
Step 1 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 2 Disable the T1 channel (values are 1 to 28) as a test port. | no t1 test channel |
You can perform the following types of loopbacks on a T1 channel:
To enable loopbacks on a T1 channel, complete the first task beginning in global configuration mode followed by any one of the following tasks:
| Task | Command |
|---|---|
Select the T1 channel (values are 1 to 28) on the CT3IP and enter interface configuration mode. | interface serial slot/port-adapter/port:t1-channel |
Enable the local loopback on the T1 channel. | |
Enable the network line loopback on the T1 channel. | |
Enable the network payload loopback on the T1 channel. | |
Enable the remote line inband loopback on the T1 channel. |
Figure 26 shows an example of a local loopback in which the loopback occurs in the T1 framer.
Figure 27 shows an example of a network line loopback in which just the data is looped back toward the network (before the T1 framer).
Figure 28 shows an example of a network payload loopback in which just the payload data is looped back toward the network at the T1 framer.
Figure 29 shows an example of a remote inband loopback in which the network line enters a line loopback.
To enable loopbacks on the T3 (and all T1 channels), complete the first task beginning in global configuration mode followed by any one of the following tasks:
| Task | Command |
|---|---|
Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Enable the local loopback. | |
Enable the network loopback. | |
Enable the remote loopback. |
After configuring the new interface, you can monitor the status and maintain the CT3IP in the Cisco 7000 series routers with an RSP7000 or in the Cisco 7500 series routers by using the show commands. To display the status of any interface, complete one of the following tasks in EXEC mode:
| Task | Command |
|---|---|
Display the internal status of each interface processor and list each interface. | |
Display the status of the T3 and T1 channels (values are 1 to 28) including the T3 alarms and T1 alarms for all 28 T1 channels or only the T1 channel specified. | show controller t3 [slot/port-adapter/port[:t1-channel]] [brief | tabular] |
Display statistics about the serial interface for the specified T1 channel (values are 1 to 28) on the router. | show interfaces serial slot/port-adapter/port:t1-channel [accounting | crb] |
| Task | Command |
Step 1 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 2 Configure the Maintenance Data Link (MDL) message. | mdl {transmit {path | idle-signal | test-signal} | string {eic | lic | fic | unit | pfi | port | generator} string} |
Use the show controllers t3 command to display MDL information (received strings). MDL information is displayed only when framing is set to C-bit.
| Task | Command |
Step 1 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
To display the remote performance report information, complete the following task in EXEC command mode:
| Task | Command |
Display the remote performance report information for the T1 channel (values are 1 to 28). | show controller t3 [slot/port-adapter/port[:t1-channel]] remote performance [brief | tabular] |
| Task | Command |
|---|---|
Step 1 Select the CT3IP and enter controller configuration mode. | controller t3 slot/port-adapter/port |
Step 2 Enable a BERT test pattern on a T1 channel (values are 1 to 28). | t1 channel bert pattern {0s | 1s | 2^15 | 2^20 | 2^23} interval minutes |
Step 3 Disable a BERT test pattern on a T1 channel (values are 1 to 28). | no t1 channel bert pattern {0s | 1s | 2^15 | 2^20 | 2^23} interval minutes |
The BERT test patterns from the CT3IP are framed test patterns (that is, the test patterns are inserted into the payload of the framed T1 signal).
To view the BERT results, use the show controller t3 or show controller t3 brief EXEC command. The BERT results include the following information:
When the T1 channel has a BERT test running, the line state is DOWN. Also, when the BERT test is running and the Status field is Not Sync, the information in the total bit errors field is not valid. When the BERT test is done, the Status field is not relevant.
The t1 bert pattern command is not written to NVRAM because it is only used for testing the T1 channel for a short predefined interval and to avoid accidentally saving the command, which could cause the interface not to come up the next time the router reboots.
You can perform the following types of remote Facility Data Link (FDL) loopbacks on a T1 channel:
To enable loopbacks on a T1 channel, complete the first task beginning in global configuration mode followed by Step 2 or Step 3 depending on the type of loopback you want to perform:
| Task | Command |
|---|---|
Step 1 Select the T1 channel (values are 1 to 28) on the CT3IP and enter interface configuration mode. | interface serial slot/port-adapter/port:t1-channel |
Step 2 Enable the remote payload FDL ANSI bit loopback on the T1 channel. | loopback remote payload [fdl] [ansi] |
Step 3 Enable the remote line FDL ANSI bit loopback on the T1 channel. | loopback remote line [fdl] [ansi] |
To configure PPP, see the "Configuring Media-Independent PPP and Multilink PPP" chapter of the Dial Solutions Configuration Guide.
The synchronous serial port adapters (PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+) on Cisco 7200 series routers support half-duplex and binary synchronous communications (Bisync). Bisync is a character-oriented data-link layer protocol for half-duplex applications. In half-duplex mode, data is sent one direction at a time. Direction is controlled by handshaking the RST and CTS control lines. These are described in the following sections:
For more information about the PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+ synchronous serial port adapters, refer to the following publications:
To configure the Bisync feature on the synchronous serial port adapters (PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+) on Cisco 7200 series routers, refer to the "Block Serial Tunnelling (BSTUN)" section of the "Configuring Serial Tunnel (STUN) and Block Serial Tunnel (BSTUN)" chapter of the Bridging and IBM Networking Configuration Guide. All commands listed in the "Block Serial Tunnelling (BSTUN)" section apply to the synchronous serial port adapters on Cisco 7200 series routers. Any command syntax that specifies an interface number supports the Cisco 7200 series slot/port syntax.
This section describes how to configure the synchronous serial port adapters (PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+) on Cisco 7200 series routers. To configure the half-duplex feature on synchronous serial port adapters, perform the tasks described in the following sections, which appear earlier in this chapter:
The SA-Comp/1 and SA-Comp/4 data compression service adapters (CSAs) are available on Cisco 7200 series routers, on second-generation Versatile Interface Processors (VIP2s) in Cisco 7500 series routers. (CSAs require VIP2 model VIP2-40.)
These service adapters provide high-performance, hardware-based data compression capabilities via simultaneous Stacker compression data compression algorithms with independent full-duplex compression and decompression capabilities on point-to-point (PPP) encapsulated packets.
The SA-Comp/1 supports up to 64 WAN interfaces and the SA-Comp/4 supports up to 256 WAN interfaces.
On the Cisco 7200 series routers you can optionally specify which CSA the interface uses to perform hardware compression.
You can configure point-to-point compression on serial interfaces that use PPP encapsulation. Compression reduces the size of a PPP frame via lossless data compression. PPP encapsulations support both predictor and Stacker compression algorithms.
If the majority of your traffic is already compressed files, do not use compression.
When you configure Stacker compression on Cisco 7200 series routers, and on Cisco 7500 series routers, there are three methods of compression: hardware compression, distributed compression, and software compression. Specifying the compress stac command with no options causes the router to use the fastest available compression method, as described here:
Using hardware compression in the CSA frees the router's main processor for other tasks. You can also configure the router to use the VIP2 to perform compression by using the distributed option, or to use the router's main processor by using the software option. If the VIP2 is not available, compression is performed in the router's main processor.
When compression is performed in software installed in the router's main processor, it might significantly affect system performance. You should disable compression in the router's main processor if the router CPU load exceeds 40 percent. To display the CPU load, use the show process cpu EXEC command.
For instructions on configuring compression over PPP, refer to the "Media-Independent PPP" chapter in the Dial Solutions Configuration Guide.
You can configure point-to-point software compression on serial interfaces that use HDLC encapsulation. Compression reduces the size of a HDLC frame via lossless data compression. The compression algorithm used is a Stacker (LZS) algorithm.
Compression is performed in software and might significantly affect system performance. We recommend that you disable compression if CPU load exceeds 65 percent. To display the CPU load, use the show process cpu EXEC command.
If the majority of your traffic is already compressed files, you should not use compression.
To configure compression over HDLC, perform the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Step 1 Enable encapsulation of a single protocol on the serial line. | |
Step 2 Enable compression. |
Real-time Transport Protocol (RTP) is a protocol used for carrying packetized audio and video traffic over an IP network. RTP is described in RFC 1889. RTP is not intended for data traffic, which uses TCP or UDP. RTP provides end-to-end network transport functions intended for applications with real-time requirements, such as audio, video, or simulation data over multicast or unicast network services.
For information and instructions for configuring RTP header compression, refer to the "Configuring IP Multicast Routing" chapter in the Network Protocol Configuration Guide, Part 1.
If you have an ATM DSU, you can invoke ATM over a serial line. You do so by mapping an ATM virtual path identifier (VPI) and virtual channel identifier (VCI) to a DXI frame address. ATM-DXI encapsulation defines a data exchange interface that allows a DTE (such as a router) and a DCE (such as an ATM DSU) to cooperate to provide a User-Network Interface (UNI) for ATM networks.
To invoke ATM over a serial line, perform the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Step 1 Specify the encapsulation method. | |
Step 2 Map a given VPI and VCI to a DXI frame address. |
You can also configure the dxi map command on a HSSI interface.
To configure an ATM interface, see the "Configuring ATM Access over a Serial Interface" chapter in the Wide-Area Networking Configuration Guide.
| Task | Command |
|---|---|
Set the length of the CRC. | crc size |
All Fast Serial Interface Processor (FSIP) interface types on the Cisco 7500 and the PA-8T and PA-4T+ synchronous serial port adapters on the Cisco 7000 series routers with RSP7000, Cisco 7200 series routers, and Cisco 7500 series routers support nonreturn-to-zero (NRZ) and nonreturn-to-zero inverted (NRZI) format. This is a line-coding format that is required for serial connections in some environments. NRZ encoding is most common. NRZI encoding is used primarily with EIA/TIA-232 connections in IBM environments.
The default configuration for all serial interfaces is NRZ format. The default is no nrzi-encoding.
To enable NRZI format, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable NRZI encoding format. |
or nrzi-encoding [mark] (Cisco 7200 series routers and Cisco 7500 series routers) |
When a DTE does not return a transmit clock, use the following interface configuration command on the Cisco 7000 series to enable the internally generated clock on a serial interface:
| Task | Command |
|---|---|
Enable the internally generated clock on a serial interface. |
If the interface on the PA-8T and PA-4T+ synchronous serial port adapters is used to drive a dedicated T1 line that does not have B8ZS encoding, you must invert the data stream on the connecting CSU/DSU or on the interface. Be careful not to invert data on both the CSU/DSU and the interface because two data inversions will cancel each other out.
If the T1 channel on the CT3IP is using AMI line coding, you must invert the data. For more information, see the t1 linecode controller command. For more information on the CT3IP, refer to the "Configure a Channelized T3 Interface Processor" section in this chapter.
To invert the data stream, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Invert the data on an interface. |
Systems that use long cables or cables that are not transmitting the TxC signal (transmit echoed clock line, also known as TXCE or SCTE clock) can experience high error rates when operating at the higher transmission speeds. For example, if the interface on the PA-8T and PA-4T+ synchronous serial port adapters is reporting a high number of error packets, a phase shift might be the problem. Inverting the clock signal can correct this shift. To invert the clock signal, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Invert the clock signal on an interface. |
It is possible to send back-to-back data packets over serial interfaces faster than some hosts can receive them. You can specify a minimum dead time after transmitting a packet to alleviate this condition. This setting is available for serial interfaces on the MCI and SCI interface cards and for the HSSI or MIP. Perform one of the following tasks, as appropriate for your system, in interface configuration mode:
| Task | Command |
|---|---|
Set the transmit delay on the MCI and SCI synchronous serial interfaces. | |
Set the transmit delay on the HSSI or MIP. | transmitter-delay hdlc-flags |
You can configure pulsing DTR signals on all serial interfaces. When the serial line protocol goes down (for example, because of loss of synchronization) the interface hardware is reset and the DTR signal is held inactive for at least the specified interval. This function is useful for handling encrypting or other similar devices that use the toggling of the DTR signal to resynchronize. To configure DTR signal pulsing, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure DTR signal pulsing. | pulse-time seconds |
This task applies to Quad Serial NIM interfaces on the Cisco 4000 series and Hitachi-based serial interfaces on the Cisco 2500 series and Cisco 3000 series.
By default, when the serial interface is operating in DTE mode, it monitors the Data Carrier Detect (DCD) signal as the line up/down indicator. By default, the attached DCE device sends the DCD signal. When the DTE interface detects the DCD signal, it changes the state of the interface to up.
In some configurations, such as an SDLC multidrop environment, the DCE device sends the Data Set Ready (DSR) signal instead of the DCD signal, which prevents the interface from coming up. To tell the interface to monitor the DSR signal instead of the DCD signal as the line up/down indicator, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure the serial interface to monitor the DSR signal as the line up/down indicator. |
 | Caution Unless you know for certain that you really need this feature, be very careful using this command. It will hide the real status of the interface. The interface could actually be down and you will not know by looking at show displays. |
On Cisco 4000 series routers, you can specify the serial Network Interface Module timing signal configuration. When the board is operating as a DCE and the DTE provides terminal timing (SCTE or TT), you can configure the DCE to use SCTE from the DTE. When running the line at high speeds and long distances, this strategy prevents phase shifting of the data with respect to the clock.
To configure the DCE to use SCTE from the DTE, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configure the DCE to use SCTE from the DTE. |
When the board is operating as a DTE, you can invert the TXC clock signal it gets from the DCE that the DTE uses to transmit data. Invert the clock signal if the DCE cannot receive SCTE from the DTE, the data is running at high speeds, and the transmission line is long. Again, this prevents phase shifting of the data with respect to the clock.
To configure the interface so that the router inverts the TXC clock signal, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify timing configuration to invert TXC clock signal. |
This section describes the optional tasks for configuring a G.703 serial interface (a serial interface that meets the G.703 electrical and mechanical specifications and operates at E1 data rates). G.703 interfaces are available on port adapters for the Fast Serial Interface Processor (FSIP) on a Cisco 4000 series or Cisco 7500 series router. Configuration tasks are described in these sections:
G.703 interfaces have two modes of operation: framed and unframed. By default, G.703 serial interfaces are configured for unframed mode. To enable framed mode, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable framed mode. | timeslot start-slot - stop-slot |
To restore the default, use the no form of this command or set the starting time slot to 0.
By default, the G.703 CRC4, which is useful for checking data integrity while operating in framed mode, is not generated. To enable generation of the G.703 CRC4, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable CRC4 generation. |
By default, time slot 16 is used for signaling. It can also be used for data. To specify the use of time slot 16 for data, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify that time slot 16 is used for data. |
A G.703 interface can clock its transmitted data from either its internal clock or from a clock recovered from the line's receive data stream. By default, the interface uses the line's receive data stream. To control which clock is used, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify the clock used for transmitted data. | clock source {line | internal} |
The Cisco Packet OC-3 Interface Processor (POSIP) is available on Cisco 7500 series routers.
The POSIP is a fixed-configuration interface processor that uses second-generation Versatile Interface Processor (VIP2) technology. The POSIP provides a single 155.520-Mbps, OC-3 physical layer interface for packet-based traffic. This OC-3 interface is fully compatible with SONET and Synchronous Digital Hierarchy (SDH) network facilities and is compliant with RFC 1619, "PPP over SONET/SDH," and RFC 1662, "PPP in HDLC-like Framing." The Packet-Over-SONET specification is primarily concerned with the use of the PPP encapsulation over SONET/SDH links.
Table 13 describes the default values set in the initial configuration of a Packet OC-3 interface.
| Attribute | Default Value |
|---|---|
Maximum transmission unit (MTU) | 4470 bytes |
Framing | SONET STS-3c framing |
Loopback internal | No internal loopback |
Loopback line | No line loopback |
Transmit clocking | Recovered receive clock |
Enabling | Shut down |
Because the Packet OC-3 interface is partially configured, you might not need to change its configuration before enabling it. However, when the router is powered up, a new Packet OC-3 interface is shut down. To enable the Packet OC-3 interface, you must enter the no shutdown command in the global configuration mode.
The values of all Packet OC-3 configuration parameters can be changed to match your network environment. Perform the optional tasks in the following sections if you need to customize the POSIP configuration:
For Packet OC-3 interface configuration examples, see the "CSU/DSU Service Module Examples" section, later in this chapter.
The Packet OC-3 interface is referred to as pos in the configuration commands. An interface is created for each POSIP found in the system at reset time.
If you need to change any of the default configuration attributes or otherwise reconfigure the Packet OC-3 interface, first complete the following task in global configuration mode:
| Task | Command |
|---|---|
Select the Packet OC-3 interface and enter interface configuration mode. | interface pos slot/port |
To set the maximum transmission unit (MTU) size for the interface, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Set the MTU size. | mtu bytes |
The value of the bytes argument is in the range 64 to 4470 bytes; the default is 4470 bytes. (4470 bytes exactly matches FDDI and HSSI interfaces for autonomous switching.) The no form of the command restores the default.
To configure framing on the Packet OC-3 interface, complete one of the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Select SDH STM-1 framing. | pos framing-sdh |
Revert to the default SONET STS-3c framing. | no pos framing-sdh |
With the loopback internal command, packets from the router are looped back in the framer. Outgoing data gets looped back to the receiver without actually being transmitted. With the loopback line command, the receive (RX) fiber is logically connected to the transmit fiber (TX) so that packets from the remote router are looped back to it. Incoming data gets looped around and retransmitted without actually being received.
To enable or disable internal loopback on the interface, complete one of the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Enable internal loopback. | loop internal |
Disable internal loopback. | no loop internal |
Local loopback is useful for checking that the POSIP is working. Packets from the router are looped back in the framer.
Line loopback is used primarily for debugging purposes.
To enable or disable an interface for line loopback, complete one of the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Enable line loopback. | loop line |
Disable line loopback. | no loop line |
The receive fiber (RX) is logically connected to the transmit fiber (TX) so that packets from the remote router are looped back to it.
By default, the Packet OC-3 interface uses the recovered receive clock to provide transmit clocking. To change the transmit clock source, complete one of the following tasks in interface configuration mode:
| Task | Command |
|---|---|
Set the internal clock as the transmit clock source. | pos internal-clock |
Set the recovered receive clock to provide transmit clocking. | no pos internal-clock |
To enable the Packet OC-3 interface when it is first installed or after it has been disabled, complete the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable the interface. | no shutdown |
You can now enter one or more network protocol addresses and otherwise configure the interface for LAN or WAN uses. For example, if IP routing is enabled on the system, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Assign an IP address and subnet mask to the interface. | ip address |
For more information about LAN network protocol configuration, see the relevant volume and chapter of the Network Protocols Configuration Guide. For information about WAN configuration, see the Wide-Area Networking Configuration Guide.
To save the new configuration to memory, complete the following task in privileged EXEC mode.
| Task | Command |
|---|---|
Write the new configuration to memory. | copy running-config startup-config |
This section describes how to configure the router to support channel service unit (CSU) and data service unit (DSU) service modules:
To configure fractional T1 and T1 (FT1/T1) service modules, perform the tasks described inthese sections:
To specify the clock source for the FT1/T1 CSU/DSU module, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify the clock source, for the CSU/DSU internal clock or the line clock. | service-module t1 clock source {internal | line} |
Data inversion is used to guarantee the ones density requirement on an alternate mark inversion (AMI) line when using bit-oriented protocols such as High-Level Data Link Control (HDLC), Point-to-Point Protocol (PPP), X.25, and Frame Relay.
To guarantee the ones density requirement on an AMI line using the FT1/T1 CSU/DSU module, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Invert bit codes by changing all 1 bits to 0 bits and all 0 bits to 1 bits. | service-module t1 data-coding inverted |
If the timeslot speed is set to 56 kbps, this command is rejected because line density is guaranteed when transmitting at 56 kbps. Use this command with the 64 kbps line speed. If you transmit inverted bit codes, both CSU/DSUs must have this command configured for successful communication.
To enable normal data transmission on a FT1/T1 network, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable normal data transmission on a T1 network. | service-module tx1 data-coding normal or no service-module t1 data-coding inverted |
To specify the frame type for a line using the FT1/T1 CSU/DSU module, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify a FT1/T1 frame type. Choose either D4 Super Frame (sf) or Extended Super Frame (esf). | service-module t1 framing {sf | esf} |
In most cases, the service provider determines which framing type, either esf or sf, is required for your circuit.
To decrease the outgoing signal strength to an optimum value for the telecommunication carrier network, perform the following task on the FT1/T1 CSU/DSU module in interface configuration mode:
| Task | Command |
|---|---|
Decrease the outgoing signal strength in decibels. | service-module t1 lbo {-15 db | -7.5 db} |
To transmit packets without decreasing outgoing signal strength, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Transmits packets without decreasing outgoing signal strength. |
The ideal signal strength should be between -15 dB and -22 dB, which is calculated by adding the phone company loss + cable length loss + line build out.
You may use this command in back-to-back configurations, but it is not needed on most actual T1 lines.
To configure the line code for the FT1/T1 CSU/DSU module, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify a line-code type. Choose alternate mark inversion (AMI) or binary 8 zero substitution (B8ZS). | service-module t1 linecode {ami | b8zs} |
Configuring B8ZS is a method of ensuring the ones density requirement on a T1 line by substituting intentional bipolar violations in bit positions four and seven for a sequence of eight zero bits. When the CSU/DSU is configured for AMI, you must guarantee the ones density requirement in your router configuration using the service-module t1 data-coding inverted command or the service-module t1 timeslots speed 56 command.
In most cases, your T1 service provider determines which line-code type, either ami or b8zs, is required for your T1 circuit.
To generate remote alarms (yellow alarms) at the local CSU/DSU or detect remote alarms sent from the remote CSU/DSU, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Enable remote alarms. |
Remote alarms are transmitted by the CSU/DSU when it detects an alarm condition, such as a red alarm (loss of signal) or blue alarm (unframed 1's). The receiving CSU/DSU then knows there is an error condition on the line.
With D4 super frame configured, a remote alarm condition is transmitted by setting the bit 2 of each time slot to zero. For received user data that has the bit 2 of each time slot set to zero, the CSU/DSU interprets the data as a remote alarm and interrupts data transmission, which explains why remote alarms are disabled by default. With Extended Super Frame configured, the remote alarm condition is signalled out of band in the facility data link.
You can see if the FT1/T1 CSU/DSU is receiving a remote alarm (yellow alarm) by issuing the show service-module command.
To disable remote alarms, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Disable remote alarms. | no service-module t1 remote-alarm-enable |
To specify if the fractional T1/T1 CSU/DSU module goes into loopback when it receives a loopback code on the line, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Configures the remote loopback code used to transmit or accept CSU loopback requests. | |
Configures the loopback code used by the local CSU/DSU to generate or detect payload-loopback commands. | service-module t1 remote-loopback payload [alternate | v54] |
You can simultaneously configure the full and payload loopback points. However, only one loopback payload code can be configured at a time. For example, if you configure the service-module t1 remote-loopback payload alternate command, a payload v.54 request, which is the industry standard and default, cannot be transmitted or accepted. Full and payload loopbacks with standard-loopup codes are enabled by default.
The no form of this command disables loopback requests. For example, the no service-module t1 remote-loopback full command ignores all full-bandwidth loopback transmissions and requests. Configuring the no form of the command may not prevent telco line providers from looping your router in esf mode, because fractional T1/T1 telcos use facilities data-link messages to initiate loopbacks.
If you enable the service-module t1 remote-loopback command, the loopback remote commands on the FT1/T1 CSU/DSU module will not be successful.
To define timeslots for FT1/T1 module, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify timeslots. | service-module t1 timeslots {range | all} [speed {56 | 64}] |
This command specifies which timeslots are used in fractional T1 operation and determines the amount of bandwidth available to the router in each timeslot.
The range specifies the DS0 timeslots that constitute the FT1/T1 channel. The range is from 1 to 24, where the first timeslot is numbered 1 and the last timeslot is numbered 24. Specify this field by using a series of subranges separated by commas. The timeslot range must match the timeslots assigned to the channel group. In most cases, the service provider defines the timeslots that comprise a channel group. Use the no form of this command to select all FT1/T1 timeslots transmitting at 64 kbps, which is the default.
To use the entire T1 line, enable the service-module T1 timeslots all command.
To configure 2- and 4-wire 56/64 kbps service modules, perform the tasks described in these sections:
In most applications, the CSU/DSU should be configured with the service-module 56k clock source line command. For back-to-back configurations, use the internal keyword to configure one CSU/DSU and use the line keyword to configure the other CSU/DSU.
To configure the clock source for a 4-wire 56/64-kbps CSU/DSU module, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Configure the clock source. | service-module 56k clock source {line | internal} |
Use the no form of this command to revert to the default clock source, which is the line clock.
To configure the network line speed for a 4-wire 56/64-kbps CSU/DSU module, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Set the network line speed. |
You can use the following line speed settings: 2.4, 4.8, 9.6, 19.2, 38.4, 56, 64 kpbs, and an auto setting.
The 64-kbps line speed cannot be used with back-to-back digital data service (DDS) lines. The subrate line speeds are determined by the service provider.
Only the 56-kbps line speed is available in switched mode. Switched mode is the default on the 2-wire CSU/DSU and is enabled by the service-module 56k network-type interface configuration command on the 4-wire CSU/DSU.
The auto linespeed setting enables the CSU/DSU to decipher current line speed from the sealing current running on the network. Because back-to-back DDS lines do not have sealing current, use the auto setting only when transmitting over telco DDS lines and using the line clock as the clock source.
Use the no form of this command to enable a network line speed of 56 kbps, which is the default.
To prevent application data from replicating loopback codes when operating at 64-kbps on a 4-wire CSU/DSU, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Scramble bit codes before transmission. |
Enable the scrambled configuration only in 64-kbps digital data service (DDS) mode. If the network type is set to switched, the configuration is refused.
If you transmit scrambled bit codes, both CSU/DSUs must have this command configured for successful communication.
To enable normal data transmission for the 4-wire 56/64-kbps module, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Specify normal data transmission. | service-module 56k data-coding normal or no service-module 56k data-coding |
To transmit packets in Digital Data Service (DDS) mode or switched dial-up mode using the 4-wire 56/64-kbps CSU/DSU module, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Transmit packets in switched dial-up mode or DDS mode. | service-module 56k network-type dds or service-module 56k network-type switched |
Use the no form of these commands to transmit from a dedicated leased line in DDS mode. DDS is enabled by default for the 4-wire CSU/DSU. Switched is enabled by default for the 2-wire CSU/DSU.
In switched mode, you need additional dialer configuration commands to configure dial-out numbers. Before you enable the service-module 56k network-type switched command, both CSU/DSU's must use a clock source coming from the line and the clock rate configured to auto or 56k kbps. If the clock rate is not set correctly, this command will not be accepted.
The 2-wire and 4-wire 56/64-kbps CSU/DSU modules use V.25 bis dial commands to interface with the router. Therefore, the interface must be configured using the dialer in-band command. DTR dial is not supported.
To enable the acceptance of a remote loopback request on a 2- or 4-wire 56/64-kbps CSU/DSU module, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Enable a remote loopback request. |
The no service-module 56k remote-loopback command prevents the local CSU/DSU from being placed into loopback by remote devices on the line. Unlike the T1 module, the 2- or 4-wire 56/64-kbps CSU/DSU module can still initiate remote loopbacks with the no form of this command configured.
To select a service provider to use with a 2- or 4-wire 56/64 kbps dial-up line, perform the following task for a serial interface in interface configuration mode:
| Task | Command |
|---|---|
Select a service provider for a 2 or 4 wire switched 56/64 kbps dialup line. | service-module 56k switched-carrier {att | other | sprint} |
The att keyword specifies AT&T or another digital network service provider as the line carrier, which is the default for the 4-wire 56/64-kbps CSU/DSU module. The sprint keyword specifies Sprint or another service provider whose network carries mixed voice and data as the line carrier, which is the default for the 2-wire switched 56-kbps CSU/DSU module.
In a Sprint network, echo-canceler tones are sent during call setup to prevent echo cancelers from damaging digital data. The transmission of these cancelers may increase call setup times by 8 seconds on the 4-wire module. Having echo cancellation enabled does not affect data traffic.
This configuration command is ignored if the network type is DDS.
Use the no form of this command to enable the default service provider. AT&T is enabled by default on the 4-wire 56/64 module. Sprint is enabled by default on the 2-wire switched 56 module.
This section describes how to configure low-speed serial interfaces. In addition to the background information described in the "Understand Half-Duplex DTE and DCE State Machines" section, these configuration guidelines are provided for configuring low-speed serial interfaces:
See the "Serial Interface Configuration Examples" section at the end of this chapter for configuration examples.
The following section describes the communication between half-duplex DTE transmit and receive state machines and half-duplex DCE transmit and receive state machines.
As shown in Figure 30, the half-duplex DTE transmit state machine for low-speed interfaces remains in the ready state when it is quiescent. When a frame is available for transmission, the state machine enters the transmit delay state and waits for a time period, which is defined by the half-duplex timer transmit-delay command. The default is 0 ms. Transmission delays are used for debugging half-duplex links and assisting lower-speed receivers that cannot process back-to-back frames.
After idling for a defined number of milliseconds, the state machine asserts a request to send (RTS) signal and changes to the wait-clear-to-send (CTS) state for the data communications equipment (DCE) to assert CTS. A timeout timer with a value set by the half-duplex timer rts-timeout command starts. This default is 3 ms. If the timeout timer expires before CTS is asserted, the state machine returns to the ready state and deasserts RTS. If CTS is asserted prior to the timer's expiration, the state machine enters the transmit state and sends the frames.
Once there are no more frames to transmit, the state machine transitions to the wait transmit finish state. The machine waits for the transmit first in first out (FIFO) in the serial controller to empty, starts a delay timer with a value defined by the half-duplex timer rts-drop-delay interface command, and transitions to the wait RTS drop delay state.
When the timer in the wait RTS drop delay state expires, the state machine deasserts RTS and transitions to the wait CTS drop state. A timeout timer with a value set by the half-duplex timer cts-drop-timeout interface command starts, and the state machine waits for the CTS to deassert. The default is 250 ms. Once the CTS signal is deasserted or the timeout timer expires, the state machine transitions back to the ready state. If the timer expires before CTS is deasserted, an error counter is incremented, which can be displayed by issuing the show controllers command for the serial interface in question.
As shown in Figure 31, a half-duplex DTE receive state machine for low-speed interfaces idles and receives frames in the ready state. A giant frame is any frame whose size exceeds the maximum transmission unit (MTU). If the beginning of a giant frame is received, the state machine transitions to the in giant state and discards frame fragments until it receives the end of the giant frame. At this point, the state machine transitions back to the ready state and waits for the next frame to arrive.
An error counter is incremented upon receipt of the giant frames. To view the error counter, enter the show interface command for the serial interface in question.
As shown in Figure 32, for a low-speed serial interface in DCE mode, the half-duplex DCE transmit state machine idles in the ready state when it is quiescent. When a frame is available for transmission on the serial interface, such as when the output queues are no longer empty, the state machine starts a timer (based on the value of the transmit-delay command, in milliseconds) and transitions to the transmit delay state. Similar to the DTE transmit state machine, the transmit delay state gives you the option of setting a delay between the transmission of frames; for example, this feature lets you compensate for a slow receiver that loses data when multiple frames are received in quick succession. The default transmit-delay value is 0 ms; use the half-duplex timer transmit-delay interface configuration command to specify a delay value not equal to 0.
After the transmit delay state, the next state depends on whether the interface is in constant-carrier mode (the default) or controlled-carrier mode.
If the interface is in constant-carrier mode, it passes through the following states:
1. The state machine passes to the transmit state when the transmit-delay timer expires. The state machine stays in the transmit state until there are no more frames to transmit.
2. When there are no more frames to transmit, the state machine passes to the wait transmit finish state, where it waits for the transmit FIFO to empty.
3. Once the FIFO empties, the DCE passes back to the ready state and waits for the next frame to appear in the output queue.
If the interface is in controlled-carrier mode, the interface performs a handshake using the data carrier detect (DCD) signal. In this mode, DCD is deasserted when the interface is idle and has nothing to transmit. The transmit state machine transitions through the states as follows:
1. After the transmit-delay timer expires, the DCE asserts DCD and transitions to the DCD-txstart delay state to ensure a time delay between the assertion of DCD and the start of transmission. A timer with the value dcd-txstart-delay is started. (This timer has a default value of 100 ms; use the half-duplex timer dcd-txstart-delay interface configuration command to specify a delay value.)
2. When this delay timer expires, the state machine transitions to the transmit state and transmits frames until there are no more frames to transmit.
3. After the DCE transmits the last frame, it transitions to the wait transmit finish state, where it waits for transmit FIFO to empty and the last frame to transmit to the wire. Then DCE starts a delay timer with the value dcd-drop-delay. (This timer has the default value of 100 ms; use the half-duplex timer dcd-drop-delay interface configuration command to specify a delay value.)
4. The DCE transitions to the wait DCD drop delay state. This state causes a time delay between the transmission of the last frame and the deassertion of DCD in the controlled-carrier mode for DCE transmits.
5. When the timer expires, the DCE deasserts DCD and transitions back to the ready state and stays there until there is a frame to transmit on that interface.
As shown in Figure 33, the half-duplex DCE receive state machine idles in the ready state when it is quiescent. It transitions out of this state when the DTE asserts RTS. In response, the DCE starts a timer with the value cts-delay. This timer delays the assertion of CTS because some DTE interfaces expect this delay. (The default value of this timer is 0 ms; use the half-duplex timer cts-delay interface configuration command to specify a delay value.)
When the timer expires, the DCE state machine asserts CTS and transitions to the receive state. It stays in the receive state until there is a frame to receive. If the beginning of a giant frame is received, it transitions to the in giant state and keeps discarding all the fragments of the giant frame and transitions back to the receive state.
Transitions back to the ready state occur when RTS is deasserted by the DTE. The response of the DCE to the deassertion of RTS is to deassert CTS and go back to the ready state.
The half-duplex controlled-carrier command enables you to change between controlled-carrier and constant-carrier modes for low-speed serial DCE interfaces in half-duplex mode. Configure a serial interface for half-duplex mode by using the half-duplex command. Full-duplex mode is the default for serial interfaces. This interface configuration is available on Cisco 2520 through Cisco 2523 routers.
Controlled-carrier operation means that the DCE interface will have DCD deasserted in the quiescent state. When the interface has something to transmit, it will assert DCD, wait a user-configured amount of time, then start the transmission. When it has finished transmitting, it will again wait a user-configured amount of time, then deassert DCD.
To place a low-speed serial interface in controlled-carrier mode, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Place a low-speed serial interface in controlled-carrier mode. |
To return a low-speed serial interface to constant-carrier mode from controlled-carrier mode, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Place a low-speed serial interface in constant-carrier mode. |
To tune half-duplex timers, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Tune half-duplex timers. | half-duplex timer {cts-delay value | cts-drop-timeout value | dcd-drop-delay value | dcd-txstart-delay value | rts-drop-delay value | rts-timeout value | transmit-delay value} |
The timer tuning commands permit you to adjust the timing of the half-duplex state machines to suit the particular needs of their half-duplex installation.
Note that the half-duplex timer command and its options deprecates the following two timer tuning commands that are available only on high-speed serial interfaces:
To specify the mode of a low-speed serial interface as either synchronous or asynchronous, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Specify the mode of a low-speed interface as either synchronous or asynchronous. | physical-layer {sync | async} |
This command applies only to low-speed serial interfaces available on Cisco 2520 through Cisco 2523 routers.
In synchronous mode, low-speed serial interfaces support all interface configuration commands available for high-speed serial interfaces, except the following two commands:
When placed in asynchronous mode, low-speed serial interfaces support all commands available for standard asynchronous interfaces. The default is synchronous mode.
Note that when you enter this command, it does not appear in the output of show running config and show startup config command, because the command is a physical-layer command.
To return to the default mode (synchronous) of a low-speed serial interface on a Cisco 2520 through Cisco 2523 router, perform the following task in interface configuration mode:
| Task | Command |
|---|---|
Return the interface to its default mode, which is synchronous. | no physical-layer |
This section includes the following example groups:
The examples in this section show how to configure the Channelized T3 Interface Processor (CT3IP). The first example shows how to configure two of the T1 channels of the channelized T3 controller. The second example shows how to configure one of the T1 channels of the channelized T3 controller as an external port for further channelization on the Multichannel Interface Processor (MIP).
For more information, refer to the "Configure the T3 Controller" and "Configure External T1 Channels" sections earlier in this chapter. Examples included in this section are:
controller t3 9/0/0 t1 16 timeslot 1-24 t1 10 timeslot 1-5,20-23 interface serial 9/0/0:16 ip address 10.20.20.1 255.255.255.0 interface serial 9/0/0:10 ip address 10.20.20.3 255.255.255.0
controller t3 9/0/0 t1 external 1 cablelength 300 controller t1 3/0 linecode b8zs channel-group 1 timeslots 1 interface serial 3/0:1 ip address 10.20.20.5 255.255.255.0
The following examples show several of the Maintenance Data Link (MDL) messages for the CT3IP in slot 9:
controller t3 9/0/0 mdl string eic Router C mdl string lic Network A mdl string fic Bldg 102 mdl string unit 123ABC
In the following example, the performance reports are generated for T1 channel 6 on the CT3IP in slot 9:
controller t3 9/0/0 t1 6 fdl ansi
The following example shows how to enable a BERT test pattern that consists of a repeating pattern of ones (...111...) and runs for 30 minutes for T1 channel 8 on CT3IP in slot 9:
controller t3 9/0/0 t1 8 bert pattern 1s interval 30
The following example shows how to enable a remote payload FDL ANSI bit loopback for T1 channel 6 on CT3IP in slot 3:
interface serial 3/0/0:6 loopback remote payload fdl ansi
These configuration examples are provided for low-speed serial interfaces:
The following example shows how to change a low-speed serial interface from synchronous to asynchronous mode:
interface serial 2 physical-layer async
The following examples show how to change a low-speed serial interface from asynchronous mode back to its default synchronous mode:
interface serial 2 physical-layer sync
interface serial 2 no physical-layer
The following example shows some typical asynchronous interface configuration commands:
interface serial 2 physical-layer async ip address 1.0.0.2 255.0.0.0 async default ip address 1.0.0.1 async mode dedicated async default routing
The following example shows some typical synchronous serial interface configuration commands available when the interface is in synchronous mode:
interface serial 2 physical-layer sync ip address 1.0.0.2 255.0.0.0 no keepalive ignore-dcd nrzi-encoding no shutdown
The following example shows how to change to controlled-carrier mode from the default of constant-carrier operation:
interface serial 2 half-duplex controlled-carrier
The following example shows how to change to constant-carrier mode from controlled-carrier mode:
interface serial 2 no half-duplex controlled-carrier
The following examples show how to set the cts-delay timer to 1234 ms and the transmit-delay timer to 50 ms.
interface serial 2 half-duplex timer cts-delay 1234 half-duplex timer transmit-delay 50
The 2T16S network processor module provides high-density serial interfaces for the Cisco 4000 series routers. This module has two high-speed interfaces that support full-duplex T1 and E1 rates (up to 2 MB per second) and 16 low-speed interfaces. The 16 lower-speed ports can be individually configured as either synchronous ports at speeds up to 128 kbps or as asynchronous ports at speeds up to 115 kbps.
For the slow-speed interfaces, both synchronous and asynchronous serial protocols are supported. For for the high-speed interfaces, only the synchronous protocols are supported. Synchronous protocols include IBM's BSC, SDLC, and HDLC. Asynchronous protocols include PPP, SLIP, and ARAP for dial-up connections using external modems.
This example shows a Cisco 4500 router equipped with two 2T16S serial network processor modules and two conventional Ethernet ports.
This router is configured for WAN aggregation using X.25, Frame Relay, PPP, and HDLC encapsulation. Serial interfaces 0, 1, 18, and 19 are the synchronous high-speed interfaces. Serial interfaces 2 through 17 and 20 through 35 are the synchronous/asynchronous low-speed interfaces.
version 11.2 ! hostname c4X00 ! username brad password 7 13171F1D0A080139 username jim password 7 104D000A0618 !
Ethernet interfaces and their subinterfaces are configured for LAN access.
interface Ethernet0 ip address 10.1.1.1 255.255.255.0 media-type 10BaseT ! interface Ethernet1 ip address 10.1.2.1 255.255.255.0 media-type 10BaseT !
Interfaces Serial 0 and Serial 1 are the high-speed serial interfaces on the first 2T16S module. In this example, subinterfaces are also configured for remote offices connected in to interface Serial 0.
interface Serial0 description Frame relay configuration sample no ip address encapsulation frame-relay ! interface Serial0.1 point-to-point description PVC to first office ip address 10.1.3.1 255.255.255.0 frame-relay interface-dlci 16 ! interface Serial0.2 point-to-point description PVC to second office ip address 10.1.4.1 255.255.255.0 frame-relay interface-dlci 17 ! interface Serial1 description X25 configuration sample ip address 10.1.5.1 255.255.255.0 no ip mroute-cache encapsulation x25 x25 address 6120184321 x25 htc 25 x25 map ip 10.1.5.2 6121230073
Serial interfaces 2 to 17 are the low-speed interfaces on the 2T16S network processor module. In this example, remote routers are connected to various configurations.
interface Serial2 description DDR connection router dial out to remote sites only ip address 10.1.6.1 255.255.255.0 dialer in-band dialer wait-for-carrier-time 60 dialer string 0118527351234 pulse-time 1 dialer-group 1 ! interface Serial3 description DDR interface to answer calls from remote office ip address 10.1.7.1 255.255.255.0 dialer in-band ! interface Serial4 description configuration for PPP interface ip address 10.1.8.1 255.255.255.0 encapsulation ppp ! interface Serial5 description Frame relay configuration sample no ip address encapsulation frame-relay ! interface Serial5.1 point-to-point description PVC to first office ip address 10.1.9.1 255.255.255.0 frame-relay interface-dlci 16 ! interface Serial5.2 point-to-point description PVC to second office ip address 10.1.10.1 255.255.255.0 frame-relay interface-dlci 17 ! interface Serial6 description configuration for PPP interface ip address 10.1.11.1 255.255.255.0 encapsulation ppp ! interface Serial7 no ip address shutdown ! interface Serial8 ip address 10.1.12.1 255.255.255.0 encapsulation ppp async default routing async mode dedicated ! interface Serial9 physical-layer async ip address 10.1.13.1 255.255.255.0 encapsulation ppp async default routing async mode dedicated ! interface Serial10 physical-layer async no ip address ! interface Serial11 no ip address shutdown ! interface Serial12 physical-layer async no ip address shutdown ! interface Serial13 no ip address shutdown ! interface Serial14 no ip address shutdown ! interface Serial15 no ip address shutdown ! interface Serial16 no ip address shutdown ! interface Serial17 no ip address shutdown
Interface serial 18 is the first high-speed serial interface of the second 2T16S module. Remote sites on different subnets are dialing in to this interface with point-to-point and multipoint connections.
interface Serial18 description Frame relay sample no ip address encapsulation frame-relay ! interface Serial18.1 point-to-point description Frame relay subinterface ip address 10.1.14.1 255.255.255.0 frame-relay interface-dlci 16 ! interface Serial18.2 point-to-point description Frame relay subinterface ip address 10.1.15.1 255.255.255.0 frame-relay interface-dlci 17 ! interface Serial18.3 point-to-point description Frame relay subinterface ip address 10.1.16.1 255.255.255.0 frame-relay interface-dlci 18 ! interface Serial18.5 multipoint ip address 10.1.17.1 255.255.255.0 frame-relay map ip 10.1.17.2 100 IETF
This second high-speed serial interface is configured to connect a X.25 link. Serial interfaces 20 through 35 are the low-speed interfaces. However, some of the interfaces are not displayed in this example.
interface Serial19 description X25 sample config ip address 10.1.18.1 255.255.255.0 no ip mroute-cache encapsulation x25 x25 address 6120000044 x25 htc 25 x25 map ip 10.1.18.2 6120170073 ! interface Serial20 ip address 10.1.19.1 255.255.255.0 ! interface Serial21 physical-layer async ip unnumbered e0 encap ppp async mode dedicated async dynamic routing ipx network 45 ipx watchdog-spoof dialer in-band dialer-group 1 ppp authentication chap ! interface Serial22 no ip address shutdown ! interface Serial23 no ip address shutdown ! interface Serial24 no ip address shutdown ! !Serial interfaces 23 through 35 would appear here. !... router eigrp 10 network 10.0.0.0 ! dialer-list 1 protocol ip permit ! line con 0 exec-timeout 15 0 password david login
The following basic line configuration configures some of the modules' low-speed serial interfaces.
line 8 10 modem InOut transport input all rxspeed 64000 txspeed 64000 flowcontrol hardware line 12 transport input all rxspeed 64000 txspeed 64000 flowcontrol hardware modem chat-script generic line 21 transport input all rxspeed 64000 txspeed 64000 flowcontrol hardware ! end
Two main categories of service module examples are provided:
FT1/T1 examples are provided for these configurations:
The following example enables super frame as the FT1/T1 frame type:
service-module t1 framing sf
The following example shows a line build out setting of -7.5 dB:
service-module t1 lbo -7.5db
The following example specifies AMI as the line-code type:
service-module t1 linecode ami
The following interactive example displays two routers connected back-to-back through an FT1/T1 line:
router# no service-module t1 remote-loopback full router# service-module t1 remote-loopback payload alternate router# loopback remote full %SERVICE_MODULE-5-LOOPUPFAILED: Unit 0 - Loopup of remote unit failed router# service-module t1 remote-loopback payload v54 router# loopback remote payload %SERVICE_MODULE-5-LOOPUPFAILED: Unit 0 - Loopup of remote unit failed router# service-module t1 remote-loopback payload alternate router# loopback remote payload %SERVICE_MODULE-5-LOOPUPREMOTE: Unit 0 - Remote unit placed in loopback
The following example displays a series of timeslot ranges and a speed of 64 kbps:
Router# service-module t1 timeslots 1-10,15-20,22 speed 64
The following example is sample output from the show service-module command:
Router1# show service-module s 0
Module type is T1/fractional
Hardware revision is B, Software revision is 1.1i,
Image checksum is 0x21791D6, Protocol revision is 1.1
Receiver has AIS alarm,
Unit is currently in test mode:
line loopback is in progress
Framing is ESF, Line Code is B8ZS, Current clock source is line,
Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.
Last user loopback performed:
remote loopback
Failed to loopup remote
Last module self-test (done at startup): Passed
Last clearing of alarm counters 0:05:50
loss of signal : 1, last occurred 0:01:50
loss of frame : 0,
AIS alarm : 1, current duration 0:00:49
Remote alarm : 0,
Module access errors : 0,
Total Data (last 0 15 minute intervals):
1466 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Data in current interval (351 seconds elapsed):
1466 Line Code Violations, 0 Path Code Violations
25 Slip Secs, 49 Fr Loss Secs, 40 Line Err Secs, 1 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 49 Unavail Secs
The following example shows how to configure a payload loopback:
Router1# loopback line payload Loopback in progress Router1# no loopback line
The following example shows the output when you loop a packet in switched mode without an active connection:
Router1# service-module 56k network-type switched Router1# loopback line payload Need active connection for this type of loopback % Service module configuration command failed: WRONG FORMAT.
The following example loops a packet from a module to the serial interface:
Router1# loopback dte Loopback in progress Router1# ping 12.0.0.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/28 ms
The following example shows a router using internal clocking while transmitting frames at 38.4 kbps:
Router1# service-module 56k clock source internal Router1# service-module 56k clock rate 38.4
2- and 4-wire 56/64 kpbs service module examples are provided for these configurations:
The following interactive example displays two routers connected in back-to-back DDS mode. However, the configuration fails because the auto rate is used.
Router1# service-module 56k clock source internal Router1# service-module 56k clock rate 38.4 Router2# service-module 56k clock rate auto % WARNING - auto rate will not work in back-to-back DDS. a1# ping 10.1.1.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) Router2# service-module 56k clock rate 38.4 Router1# ping 10.1.1.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 52/54/56 ms
When transferring from DDS mode to switched mode, you must set the correct clock rate, as shown in the following example:
Router2# service-module 56k network-type dds Router2# service-module 56k clock rate 38.4 Router2# service-module 56k network-type switched % Have to use 56k or auto clock rate for switched mode % Service module configuration command failed: WRONG FORMAT. Router2# service-module 56k clock rate auto % WARNING - auto rate will not work in back-to-back DDS. Router2# service-module 56k network-type switched
The following example scrambles bit codes in 64 kbps DDS mode:
Router# service-module 56k clock rate 56 Router# service-module 56k data-coding scrambled Can configure scrambler only in 64k speed DDS mode % Service module configuration command failed: WRONG FORMAT. Router# service-module 56k clock rate 64 Router# service-module 56k data-coding scrambled
The following example displays transmission in switched dial-up mode:
Router# service-module 56k clock rate 19.2 Router# service-module 56k network-type switched % Have to use 56k or auto clock rate for switched mode % Service module configuration command failed: WRONG FORMAT. Router# service-module 56k clock rate auto Router# service-module 56k network-type switched Router# dialer in-band Router# dialer string 2576666 Router# dialer-group 1
The following example is sample output from the show service-module serial command:
Router1# show service-module serial 1
Module type is 4-wire Switched 56
Hardware revision is B, Software revision is X.07,
Image checksum is 0x45354643, Protocol revision is 1.0
Connection state: active,
Receiver has loss of signal, loss of sealing current,
Unit is currently in test mode:
line loopback is in progress
Current line rate is 56 Kbits/sec
Last user loopback performed:
dte loopback
duration 00:00:58
Last module self-test (done at startup): Passed
Last clearing of alarm counters 0:13:54
oos/oof : 3, last occurred 0:00:24
loss of signal : 3, current duration 0:00:24
loss of sealing curren: 2, current duration 0:04:39
loss of frame : 0,
rate adaption attempts: 0,
The following example enables you to transmit and receive remote loopbacks using the service-module 56k remote-loopback command:
service-module 56k remote-loopback
The following example selects AT&T as the service provider:
service-module 56k network-type switched service-module 56k switched-carrier att
Posted: Thu Mar 11 11:42:36 PST 1999
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