Multilink Point-to-Point Protocol (MLPPP) is supported on the 1-Port Channelized OC-12/DS0 SPAs. MLPPP provides a method for combining multiple physical links into one logical link. The implementation of MLPPP combines multiple PPP serial interfaces into one multilink interface. MLPPP performs the fragmenting, reassembling, and sequencing of datagrams across multiple PPP links. MLPPP is supported on the 2-Port and 4-Port Channelized T3 SPAs.

MLPPP provides the same features that are supported on PPP Serial interfaces with the exception of QoS. It also provides the following additional features:

• Fragment sizes of 128, 256, and 512 bytes
• Long sequence numbers (24-bit)
• Lost fragment detection timeout period of 80 ms
• Minimum-active-links configuration option
• LCP echo request/reply support over multilink interface
• Full T1 and E1 framed and unframed links

The Local Management Interface (LMI) protocol monitors the addition, deletion, and status of PVCs. LMI also verifies the integrity of the link that forms a Frame Relay UNI interface. By default, cisco LMI is enabled on all PVCs.

If the LMI type is cisco(the default LMI type), the maximum number of PVCs that can be supported under a single interface is related to the MTU size of the main interface. Use the following formula to calculate the maximum number of PVCs supported on a card or SPA:

(MTU - 13)/8 = maximum number of PVCs

Note	The default setting of the mtu command for a serial interface is 1504 bytes. Therefore, the default numbers of PVCs supported on a serial interface configured with cisco LMI is 186.

To specify a synchronous serial interface and enter interface configuration mode, use one of the following commands in global configuration mode.

Router(config)# interface serial  number

Router(config)# interface serial  slot / port

Router(config)# interface serial  slot / port-adapter / port

Router(config)# interface serial  slot / port:channel-group

Router(config)# interface serial  number:channel-group

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:

• ATM-DXI
• HDLC
• Frame Relay
• PPP
• Synchronous Data Link Control (SDLC)
• SMDS
• Cisco Serial Tunnel ( STUN)
• X.25-based encapsulations

To define the encapsulation method, use the following command in interface configuration mode.

Router(config-if)# encapsulation {atm-dxi | hdlc | frame-relay | ppp | sdlc-primary | sdlc-secondary | smds | stun | x25}

Note	You cannot use the physical-layer async command for frame-relay encapsulation.

Encapsulation methods are set according to the type of protocol or application you configure in the Cisco IOS software.

• ATM-DXI is described in the Configuring the CRC.
• PPP is described in the " Configuring Media-Independent PPP and Multilink PPP " chapter in the Cisco IOS Dial Technologies Configuration Guide .
• ATM, Frame Relay, and X.25 information and configuration steps are described in the Cisco IOS Asynchronous Transfer Mode Configuration Guide and the Cisco IOS Wide-Area Networking Configuration Guide .
• 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 Cisco IOS Interface and Hardware Component Command Reference , under the encapsulation command.

By default, synchronous interfaces operate in full-duplex mode. To configure an SDLC interface for half-duplex mode, use the following command in interface configuration mode.

Router(config-if)# half-duplex

Binary synchronous communication (Bisync) 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 sends the last block again if there is no response from the secondary within the period of block receive timeout.

To configure the serial interface for full-duplex mode, use the following command in interface configuration mode.

Router(config-if)# full-duplex

To configure PPP, refer to the " Configuring Media-Independent PPP and Multilink PPP " chapter in the CiscoIOS Dial Technologies 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 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 Request to Send (RST) and Clear to Send (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:

• PA-8T-V35 Synchronous Serial Port Adapter Installation and Configuration
• PA-8T-X21 Synchronous Serial Port Adapter Installation and Configuration
• PA-8T-232 Synchronous Serial Port Adapter Installation and Configuration
• PA-4T+ Synchronous Serial Port Adapter Installation and Configuration

• Configuring Bisync
• Configuring Half-Duplex Carrier Modes and Timers

The SA-Comp/1 and SA-Comp/4 data compression service adapters (CSAs) are available on:

• Cisco 7200 series routers
• Second-generation Versatile Interface Processors (VIP2s) in Cisco 7500 series routers (CSAs require VIP2 model VIP2-40.)

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.

Note	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:

• If the router contains a compression service adapter (CSA), compression is performed in the CSA hardware (hardware compression).
• If the CSA is not available, compression is performed in the software installed on the VIP2 (distributed compression).
• If the VIP2 is not available, compression is performed in the router's main processor (software compression).

Using hardware compression in the CSA frees the main processor of the router for other tasks. You can also configure the router to use the VIP2 to perform compression by using the distributed option on the compress command, or to use the main processor of the router by using the software option on the compress command. If the VIP2 is not available, compression is performed in the main processor of the router.

When compression is performed in software installed in the main processor of the router, 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 " Configuring Media-Independent PPP and Multilink PPP " chapter in the CiscoIOS Dial Technologies Configuration Guide .

1.    Router(config-if)# encapsulation hdlc

2.    Router(config-if)# compress stac

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--A Transport Protocol for Real-Time Applications . RTP is not intended for data traffic, which uses TCP or UDP (User Datagram Protocol). 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 Cisco IOS IP Multicast Configuration Guide .

The data compression Advanced Interface Module (AIM) provides hardware-based compression and decompression of packet data transmitted and received on the serial network interfaces of the Cisco 2600 series router without occupying the Port Module Slot which might otherwise be used for additional customer network ports. Supported are the industry standard Lempel-Ziv Stac (LZS) and Microsoft point-to-point compression (MPPC) compression algorithms over point-to-point protocol (PPP) or Frame Relay. High-level Data Link Control (HDLC) is not supported. The data compression AIM requires Cisco IOS Release 12.0(1)T or later.

The data compression AIM is a daughtercard assembly that attaches directly to the Cisco 2600 motherboard leaving the single network module slot available for other purposes. The data compression AIM supports only serial interfaces using PPP encapsulation with STAC or MPPC compression, or Frame Relay encapsulation with STAC compression. No routing, bridging, or switching performance is impacted by this feature. The data compression AIM module contains a high-performance data compression coprocessor that implements the LZS and MPPC data compression algorithms. The module provides compression support for up to two E1 lines. The module contains a PCI Target/Initiator system bus interface for access into host system memory with minimal Host processor intervention.

To configure the data compression AIM daughtercard assembly, perform the following tasks:

• Configuring PPP Compression
• Verifying PPP Compression
• Configuring Frame Relay Map Compression
• Verifying Frame Relay Map Compression
• Configuring Frame Relay Payload Compression
• Verifying Frame Relay Payload Compression
• Configuring Diagnostics
• Verifying Diagnostics

The cyclic redundancy check (CRC) on a serial interface defaults to a length of 16 bits. To change the length of the CRC to 32 bits on an Fast Serial Interface Processor (FSIP) or HSSI Interface Processor (HIP) of the Cisco 7500 series only, use the following command in interface configuration mode.

Router (config-if)# crc  size

The nonreturn-to-zero (NRZ) and nonreturn-to-zero inverted (NRZI) formats are supported on:

• All FSIP interface types on Cisco 7500 series routers
• PA-8T and PA-4T+ synchronous serial port adapters on:
  • Cisco 7000 series routers with RSP7000
  • Cisco 7200 series routers
  • Cisco 7500 series routers

NRZ and NRZI are line-coding formats that are 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, use one of the following commands in interface configuration mode.

Router(config-if)# nrzi-encoding

Router(config-if)# nrzi-encoding [mark]

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:

Router(config-if)# transmit-clock-internal

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 alternate mark inversion (AMI) line coding, you must invert the data. For more information, refer to the t1 linecode controller configuration command. For more information on the CT3IP, see the Configuring a Channelized T3 Interface Processor.

To invert the data stream, use the following command in interface configuration mode.

Router(config-if)# invert data

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, use the following commands in interface configuration mode.

Router(config-if)# invert txclock 

Router(config-if)# invert rxclock

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 remove this condition. This setting is available for serial interfaces on the MCI and SCI interface cards and for the HSSI or MIP. Use one of the following commands, as appropriate for your system, in interface configuration mode.

Router(config-if)# transmitter-delay microseconds

Router(config-if)# transmitter-delay  hdlc-flags

You can configure pulsing dedicated Token Ring (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 reset synchronization. To configure DTR signal pulsing, use the following command in interface configuration mode.

Router(config-if)# pulse-time  seconds

This task applies to:

• Quad Serial NIM (network interface module) interfaces on the Cisco 4000 series
• 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, use the following command in interface configuration mode.

Router(config-if)# ignore-dcd

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, use the following command in interface configuration mode.

Router(config-if)# dce-terminal-timing enable

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, use the following command in interface configuration mode.

Router(config-if)# dte-invert-txc

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.

The E1-G.703/G.704 serial port adapters (PA-4E1G-120 and PA-4E1G-75) are available on:

• Cisco 7500 series routers
• Cisco 7200 series routers
• Cisco 7000 series routers with the 7000 series Route Switch Processor (RSP7000) and 7000 series Chassis Interface (RSP7000CI)

These port adapters provide up to four E1 synchronous serial interfaces, which are compatible with and specified by G.703/G.704. The PA-4E1G-120 supports balanced operation, and the PA-4E1G-75 supports unbalanced operation with 15-pin, D-shell (DB-15) receptacles on the port adapters. Both port adapters operate in full-duplex mode at the E1 speed of 2.048 Mbps.

Configuration tasks are described in the following sections:

• Enabling Framed Mode
• Enabling CRC4 Generation
• Using Time Slot 16 for Data
• Specifying a Clock Source

1.    Router> enable

2.    Router# configure terminal

3.    Router(config)# controller t3 shelf / slot / port

4.    Router(config-controller)# description ascii-string

5.    Router(config-controller)# cablelength number

6.    Router(config-controller)# framing {c-bit | m23}

7.    Router(config-controller)# t1 ds1 controller

8.    Router(config-controller)# exit

9.    Router(config)# controller t1 shelf / slot / port:t1-num

10.    Router(config-controller)# exit

11.    Router(config)# dial-tdm-clock priority number {external | trunk-slot number} ds3-port number port number

12.    Router(config)# exit

13.    Router# copy running-config startup-config

If you do not modify the configuration of the CT3IP, the configuration defaults shown in the table below are used.

If you must change any of the default configuration attributes, use the following commands beginning in global configuration mode.

Router(config)# controller t3  slot / port-adapter / port

Router(config-controller)# framing {c-bit | m23 | auto-detect}

Router(config-controller)# cablelength feet

Router(config-controller)# clock source {internal | line}

1.    Router(config)# controller t3 slot / port-adapter / port

2.    Router(config-controller)# t1 channel timeslot range [speed {56 | 64}]

Note	The 56-kbps speed is valid only for T1 channels 21 through 28.

Note	T1 channels on the CT3IP are numbered 1 to 28 rather than the more traditional zero-based scheme (0 to 27) used with other Cisco products. This numbering scheme is to ensure consistency with telco numbering schemes for T1 channels within channelized T3 equipment.

If you need to change any of the default configuration attributes, use the following commands, beginning in global configuration mode.

Router(config)# controller t3  slot / port-adapter / port

Router(config-controller)# t1 channel framing {esf | sf}

Router(config-controller)# no t1 channel yellow {detection | generation}

Router(config-controller)# t1 channel clock source {internal | line}

Router(config-controller)# t1 channel linecode {ami | b8zs}

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 Configuring a Synchronous Serial Interface.

To enter interface configuration mode and configure the serial interface that corresponds to a T1 channel, use the following command in global configuration mode.

Router(config)# interface serial  slot / port-adapter / port:t1-channel

In addition to the commands in the Configuring a Synchronous Serial Interface, 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 datainterface command, see the Inverting the Data. For more information, refer to the t1 linecode controller configuration command in the Cisco IOS Interface and Hardware Component Command Reference.

The first three T1 channels (1, 2, and 3) of the CT3IP can be broken out to the DSUP-15 connectors so that the T1 channel can be further demultiplexed by the MIP on the same router, another router, or other multiplexing equipment.

Note

If a T1 channel that was previously configured as a serial interface is broken out to the external T1 port, that interface and its associated configuration remain intact while the channel is broken out to the external T1 port. The serial interface is not usable during the time that the T1 channel is broken out to the external T1 port; however, the configuration remains to facilitate the return of the T1 channel to a serial interface using the no t1 external command.

To configure a T1 channel as an external port, use the following commands beginning in EXEC mode.

1.    Router# show controller t3 slot / port-adapter / port

2.    Router# configure terminal

3.    Router(config)# controller t3 slot / port-adapter / port

4.    Router(config-controller)# 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, use the following command in global configuration mode.

Router(config)# 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, use the following command in global configuration mode.

Router(config)# interface serial  slot / port:t1-channel

For more information, see the Configuring Each T1 Channel and the Specifying a Synchronous Serial Interface.

For an example of configuring an external T1 channel, see the Channelized T3 Interface Processor Configuration Examples.

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, use one of the following commands in EXEC mode.

Router> show controller cbus

Router> show controller t3

[slot / port-adapter / port[: t1-channel]]

[brief | tabular]

Router> show interfaces serial

                
                  slot
                
                
                  /
                
                
                  port-adapter
                
                
                  /
                
                
                  port
                
                
                  :
                
                
                  t1-channel
                
              

[accounting | crb]

To verify your software configuration, you can use show commands for controller settings. To use show commands, you must be in privileged EXEC mode.

Router# 
show controller t3
T3 1/0/0 is up.
 Applique type is Channelized T3
 No alarms detected.
 FEAC code received: No code is being received
 Framing is M23, Line Code is B3ZS, Clock Source is Line.
 Data in current interval (751 seconds elapsed):
     0 Line Code Violations, 0 P-bit Coding Violation
     0 C-bit Coding Violation, 0 P-bit Err Secs
     0 P-bit Severely Err Secs, 0 Severely Err Framing Secs
     0 Unavailable Secs, 0 Line Errored Secs
     0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
 Total Data (last 16 15 minute intervals):
     0 Line Code Violations, 0 P-bit Coding Violation,
     0 C-bit Coding Violation, 0 P-bit Err Secs,
     0 P-bit Severely Err Secs, 0 Severely Err Framing Secs,
     0 Unavailable Secs, 0 Line Errored Secs,
     0 C-bit Errored Secs, 0 C-bit Severely Errored Secs

Tip	To use the controller, it must report being up.

• No errors should be reported.

1.    Router(config)# controllers t3 slot / port-adapter / port

2.    Router(config-controller)# mdl {transmit {path | idle-signal | test-signal} | string {eic | lic | fic | unit | pfi | port | generator} string}

Specify one mdl command for each message. For example, use mdl string eic Router A to transmit "Router A" as the equipment identification code and use mdl string lic Test Network to transmit "Test Network" as the location identification code.

Use the show controllers t3command to display MDL information (received strings). MDL information is displayed only when framing is set to C-bit.

1.    Router(config)# controllers t3 slot / port-adapter / port

2.    Router(config-controller)# t1 channel fdl ansi

Note	Performance reporting is available only on T1 channels configured for ESF framing.

To display the remote performance report information, use the following command in EXEC mode.

Router> show controllers t3 [slot / port-adapter / port[: t1-channel]] remote performance [brief | tabular]

1.    5300> enable

2.    5300# configure terminal

3.    Router(config)# bert profile

To verify that a BERT feature is running, use the show running-configcommand in EXEC mode.

5300> show running-config
!
bert profile 1 pattern 1s threshold 10^-4 error-injection none duration 3
bert profile 7 pattern 220-O.151QRSS threshold 10^-3 error-injection 10^-5 duration 120

1.    Router(config)# controller t3 slot / port-adapter / port

2.    Router(config-controller)# t1 channel bert pattern {0s | 1s | 2^15 | 2^20| 2^23} interval minutes

3.    Router(config-controller)# 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 controllers t3 or show controllers t3 brief EXEC command. The BERT results include the following information:

• Type of test pattern selected
• Status of the test
• Interval selected
• Time remaining on the BERT test
• Total bit errors
• Total bits received

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.

1.   Do one of the following:

2.    Router(config-if)# loopback remote payload [fdl] [ansi]

3.    Router(config-if)# loopback remote line fdl {ansi | bellcore}

Note	The port adapter and port numbers for the CT3IP are 0.

When you configure your channelized T1 trunk cards, you can change the line build-out of the cable pair connected to the port. To specify the build-out value, use either the cablelength long command or the cablelength shortcommand. These commands are not required for E1 trunk cards.

For cables longer than 655 feet, use the cablelength long command; for cables up to and including 655 feet, use the cablelength shortcommand.

The line-termination command allows you to set the T1/E1 port termination to 75 ohms unbalanced or 120 ohms balanced.

The following cable length short configurations define the length range (in feet) between your network access server (NAS) and your repeater. The cablelength short command is configured for a channelized T1 only and includes the following settings:

• 133 feet (0 to 133 feet)
• 266 feet (134 to 266 feet)
• 399 feet (267 to 399 feet)
• 533 feet (400 to 533 feet)
• 655 feet (534 to 655 feet)

Note

Although you can specify a cable length from 0 to 655 feet, the hardware only recognizes fixed configuration lengths. For example, if your cable length is 50 feet between your NAS and your repeater, you should configure your cable length using the 133-feet setting. If you later change the cable length to 200 feet, you should reconfigure your cable length using the 266-feet setting.

The following cable length long configurations define the length range in gain and pulse requirements for the length of build-out between your NAS and your repeater that is longer than 655 feet. The cablelength long command is configured for a channelized T1 only and includes the following gain and pulse settings:

• gain26 (26 dB gain)
• gain36 (36 dB gain)
• -15db (-15 dB pulse)
• -22.5db (-22.5 dB pulse)
• -7.5db (-7.5 dB pulse)
• 0db (0 dB pulse)

To configure channelized T1 lines for line build-out, use the following commands beginning in user EXEC mode.

1.    Router> enable

2.    Router# configure terminal

3.    Router(config)# controller t1 shelf / slot / port

4.   Do one of the following:

5.    Router(config-controller)# line termination {75-ohm | 120-ohm}

The commands listed in the table below have been added to support the PA-E3 interface configuration. If you do not modify the configuration of the PA-E3, the configuration defaults shown in the table below are used.

                
                  dsu bandwidth
              

                
                  dsu mode
              

                
                  framing
                
              

                
                  international bit
              

                
                  invert data
              

                
                  national bit
              

                
                  scramble
                
              

If you need to change any of the default configuration attributes, use the first command in global configuration mode, followed by any of the optional commands in interface configuration mode.

Router(config)# interface serial  slot / port-adapter / port

Router(config)# interface serial  slot / port

Router(config-if)# dsu bandwidth  kbps

Router(config-if)# dsu mode {0 | 1}

Router(config-if)# framing {g751 | bypass}

Router(config-if)# international bit {0 | 1} {0 | 1}

Router(config-if)# invert data

Router(config-if)# national bit {0 | 1}

Router(config-if)# scramble

After configuring the new interface, you can display its status. To show current status of the E3 interface on the PA-E3 port adapter, use any of the following commands in EXEC mode.

Router> show interfaces serial  slot / port-adapter / port

Router> show interfaces serial  slot / port

Router> show controllers serial slot / port-adapter / port

Router> show controllers serial slot / port

The commands listed in the table below have been added to support the PA-T3 interface configuration. If you do not modify the configuration of the PA-T3, the configuration defaults shown in the table below are used.

                
                  cablelength
                
              

                
                  clock source
              

                
                  crc 32
              

                
                  dsu bandwidth
              

                
                  dsu mode
              

                
                  framing
                
              

                
                  invert data
              

                
                  scramble
                
              

If you need to change any of the default configuration attributes, use the first command in global configuration mode, followed by any of the optional commands in interface configuration mode.

Router(config)# interface serial  slot / port-adapter / port

Router(config)# interface serial  slot / port

Router(config-if)# cablelength length

Router(config-if)# crc 32

Router(config-if)# dsu bandwidth  kbps

Router(config-if)# dsu mode {0 | 1 | 2}

Router(config-if)# framing {c-bit | m13 | bypass}

Router(config-if)# invert data

Router(config-if)# scramble

To set the following loopback modes to troubleshoot the PA-T3 port adapter using Cisco IOS software, use the first command in global configuration mode, followed by any of the other commands depending on your needs:

Router(config)# loopback dte

Router(config)# loopback local

Router(config)# loopback network line

Router(config)# loopback network payload

Router(config)# loopback remote

These loopback commands loop all packets from the T3 interface back to the interface or direct packets from the network back out toward the network.

After configuring the new interface, you can display its status. To show current status of the T3 interface on the PA-T3 port adapter, use any of the following commands in EXEC mode.

Router> show version

Router> show controllers cbus

Router> show interfaces  slot / port-adapter / port

Router> show interfaces  slot / port

Router> show controllers serial slot / port-adapter / port

Router> show controllers serial  slot / port

Router> show protocols

Router> more system:running-config

Router> more nvram:startup-config

Router> show diag slot

The Packet OC-3 interface is referred to as pos in the configuration commands. An interface is created for each POS 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, use one the following commands in global configuration mode.

Router(config)# interface pos  slot / port

Router(config)# interface pos  slot / port-adapter / port 

To set the maximum transmission unit (MTU) size for the interface, use the following command in interface configuration mode.

Router(config-if)# 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.

Caution

Changing an MTU size on a Cisco 7500 series router will result in resizing and reassignment of buffers and resetting of all interfaces. The following message is displayed: %RSP-3-Restart:cbus complex88

To configure framing on the Packet OC-3 interface, use one of the following commands in interface configuration mode.

Router(config-if)# pos framing-sdh 

Router(config-if)# 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 fiber (RX) 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, use one of the following commands in interface configuration mode.

Router(config-if)# loop internal

Router(config-if)# no loop internal

Local loopback is useful for checking that the POS 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, use one of the following commands in interface configuration mode.

Router(config-if)# loop line

Router(config-if)# 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, use one of the following commands in interface configuration mode.

Router(config-if)# clock source

Router(config-if)# no clock source

SONET payload scrambling applies a self-synchronous scrambler (x43+1) to the Synchronous Payload Envelope (SPE) of the interface to ensure sufficient bit transition density. Both ends of the connection must use the same scrambling algorithm. When enabling POS scrambling on a VIP2 POS on the Cisco 7500 series router that has a hardware revision of 1.5 or higher, you can specify CRC 16 only (that is, CRC 32 is currently not supported).

To enable SONET payload scrambling on a POS interface, use the following command in interface configuration mode.

Router(config-if)# pos scramble-atm

To configure line alarm indication signals (LAIS) when the POS interface is placed in any administrative shut down state, use the following command in interface configuration mode.

Router(config-if)# pos ais-shut

1.    Router# show running-config

2.    Router# configure terminal

3.    Router(config)# ip routing

4.    Router(config)# interface srp slot / port

5.    Router(config-if)# ip address ip-address mask

6.    Add any additional configuration commands required to enable routing protocols, and set the interface characteristics for your configuration requirements.

7.    Router(config-if)# no shutdown

8.    Router(config-if)# exit

9.    Router# copy running-config startup-config

The system displays an OK message when the configuration has been stored.

Use the show running-config command to verify the currently running configuration. Use the show version command to display the configuration of the system hardware and the Cisco IOS software information.

1.    Router# configure terminal

2.    Router(config)# interface srp slot / port

3.    Router(config-if)# srp ips request manual-switch a

4.    Router(config-if)# srp ips wtr-timer 10

5.    Router(config-if)# srp ips timer 20 a

6.    Router(config-if)# exit

Use the show srp command to verify the configuration.

1.    Router# configure terminal

2.    Router(config)# interface srp slot / port

3.    Router(config-if)# srp topology-timer 70

4.    Router(config-if)# exit

5.    Router# show srp topology

1.    Router(config)# interface pos slot / port-adapter / port

2.    Router(config-if)# aps working circuit-number

3.    Router(config-if)# end

4.    Router# show controllers pos

Note	If a router has two or more protect interfaces, the aps group command for each interface must precede the corresponding aps protectcommand.

To configure the protect interface, use the following commands beginning in global configuration mode.

1.    Router(config)# interface pos slot / port-adapter / port

2.    Router(config-if)# aps protect circuit-number ip-address

3.    Router(config-if)# end

4.    Router# show controllers pos

To configure the other APS options, use any of the following optional commands in interface configuration mode.

Router(config-if)# aps authenticate  string

Router(config-if)# aps force circuit-number

Router(config-if)# aps group  group-number

Router(config-if)# aps lockout circuit-number

Router(config-if)# aps manual circuit-number

Router(config-if)# aps revert minutes

Router(config-if)# aps timers  seconds1 seconds2

Router(config-if)# aps unidirectional

To provide information about system processes, the Cisco IOS software includes an extensive list of EXEC commands that begin with the word show, which, when executed, display detailed tables of system information. Following is a list of some of the common show commands for the APS feature.

To display the information described, use these commands in privileged EXEC mode.

Router# show aps

Router# show controllers pos

Router# show interfaces pos 

To configure the thresholds and the type of SONET alarms that are reported, use any of the following commands in interface configuration mode. The commands listed in this section are optional. The default settings are adequate for most POS installations.

Router(config-if)# pos threshold {b1-tca | b2-tca | b3-tca | sd-ber | sf-ber} rate

Router(config-if)# pos report {b1-tca | b2-tca | b3-tca | lais | lrdi | pais | plop | prdi | rdool | sd-ber | sf-ber | slof | slos} 

To display the current BER threshold setting or to view the reporting of the SONET alarms, use the show controllers pos EXEC command.

LAIS can be used to force a protection switch in an APS environment. To force an APS switch when the interface is placed in administrative shut down state, use the following command in interface configuration mode.

Router(config-if)# pos ais-shut

To specify the clock source (that is, the source of the timing synchronization signal) for the FT1/T1 CSU/DSU module, use the following command in interface configuration mode.

Router(config-if)# 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), PPP, X.25, and Frame Relay.

To guarantee the ones density requirement on an AMI line using the FT1/T1 CSU/DSU module, use the following command in interface configuration mode.

Router(config-if)# service-module t1 data-coding inverted 

If the time-slot 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 an FT1/T1 network, use the following command in interface configuration mode.

Router(config-if)# service-module tx1 data-coding normal

Router(config-if)# no service-module t1 data-coding inverted 

To specify the frame type for a line using the FT1/T1 CSU/DSU module, use the following command in interface configuration mode.

Router(config-if)# service-module t1 framing {sf | esf}

In most cases, the service provider determines which framing type, either sf or esf, is required for your circuit.

To decrease the outgoing signal strength to an optimum value for the telecommunication carrier network, use the following command on the FT1/T1 CSU/DSU module in interface configuration mode.

Router(config-if)# service-module t1 lbo {-15 db | -7.5 db}

To transmit packets without decreasing outgoing signal strength, use the following command in interface configuration mode.

Router(config-if)# service-module t1 lbo none

The ideal signal strength should be between -15 dB and -22 dB, which is calculated by adding the phone company loss plus cable length loss plus 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, use the following command in interface configuration mode.

Router(config-if)# 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 you configure the CSU/DSU AMI, you must guarantee the ones density requirement in your router using the service-module t1 data-coding inverted command or the service-module t1 timeslots speed 56command. 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 to detect remote alarms sent from the remote CSU/DSU, use the following command in interface configuration mode.