Table Of Contents

Serial Interface Commands on Cisco IOS XR Software

crc (serial)

encapsulation (serial)

fragment end-to-end

interface serial

keepalive (serial)

invert

pvc (serial)

scramble

serial

transmit-delay (serial)

Serial Interface Commands on Cisco IOS XR Software

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This module describes the commands used to configure serial interfaces on routers supporting
Cisco IOS XR software.

crc (serial)

To set the length of the cyclic redundancy check (CRC) on a serial interface, use the crc command in serial configuration mode. To return the CRC setting on a serial interface to the default setting, use the no form of this command.

crc {16 | 32}

no crc {16 | 32}

Syntax Description

16	Sets 16-bit CRC mode.
32	Sets 32-bit CRC mode.

Defaults

16 bits is the default for serial interfaces.

Command Modes

Serial configuration

Command History

Release	Modification
Release 3.3.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The designators 16 and 32 indicate the length (in bits) of the frame check sequence (FCS). A CRC of 32 bits provides more powerful error detection, but adds overhead. Both the sender and receiver must use the same setting.

CRC-16, the most widely used error checking method throughout the United States and Europe, is used extensively with WANs. CRC-32 is specified by IEEE standard 802 and as an option by some point-to-point transmission standards. It is often used on Switched Multimegabit Data Service (SMDS) networks and LANs.

Task ID

Task ID	Operations
hdlc	read, write

Examples

In the following example, the 32-bit CRC on serial interface 0/3/0/0/0:10 is enabled:

RP/0/0/CPU0:Router(config)# interface serial 0/3/0/0/0:10

RP/0/0/CPU0:Router(config-if)# serial

RP/0/0/CPU0:Router(config-if-serial)# crc 32

Related Commands

Command	Description
show interfaces	Displays statistics for all interfaces configured on the router or on a specific node.

encapsulation (serial)

To set the Layer 2 encapsulation of an interface, use the encapsulation command in interface configuration mode. To restore the system to the default encapsulation, use the no form of this command.

encapsulation {hdlc | ppp | frame-relay}

no encapsulation

Syntax Description

hdlc	Enables Cisco High-Level Data Link Control (cHDLC) encapsulation on the interface. This is the default encapsulation type.
ppp	Enables Point-to-Point Protocol (PPP) encapsulation on the interface.
frame-relay	Enables Frame Relay encapsulation on the interface.

Defaults

For serial interfaces, the default encapsulation is HDLC.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was first supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	Frame Relay encapsulation was supported on serial interfaces.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Task ID

Task ID	Operations
hdlc	read, write
interface	read, write

Examples

In the following example, PPP encapsulation is set on serial interface 0/3/0/1:

RP/0/RP0/CPU0:router(config)# interface serial 0/3/0/1

RP/0/RP0/CPU0:router(config-if)# encapsulation ppp

Related Commands

Command	Description
show interfaces	Displays statistics for all interfaces configured on the router.
show ppp interfaces	Displays PPP state information for an interface.

fragment end-to-end

To enable fragmentation of Frame Relay frames on an interface, use the fragment end-to-end command in interface configuration mode. To disable Frame Relay fragmentation, use the no form of this command.

fragment end-to-end fragment-size

no fragment end-to-end

Syntax Description

fragment-size

Specifies the number of payload bytes from the original Frame Relay frame that will go into each fragment. This number excludes the Frame Relay header of the original frame. All the fragments of a Frame Relay frame except the last will have a payload size equal to fragment-size; the last fragment will have a payload less than or equal to fragment-size. Valid values are from 16 to 1600 bytes.

Defaults

The default fragment size is 53.

Command Modes

Global configuration

Command History

Release	Modification
Release 3.5.0	This command was introduced on the Cisco XR 12000 Series Router.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Task ID

Task ID	Operations
interface	read, write

Examples

The following example shows how to enter interface configuration mode for a serial interface in slot 6, subslot 2, port 4, T1 channel number 10 and channel group 8:

RP/0/0/CPU0:Router(config)# interface serial 0/6/2/4.1 l2transport

RP/0/0/CPU0:Router(config-if)# pvc 100

interface serial

To configure a serial interface and enter interface or subinterface configuration mode, use the interface serial command in global configuration mode.

interface serial instance[.subinterface {point-to-point | l2transport}]

Syntax Description

instance	Serial interface instance. Naming notation for T3/E3 interfaces is rack/slot/module/port; naming notation for T1/E1/DS0 interfaces is rack/slot/module/port/t1-num:channel-group-number. A slash between values is required as part of the notation. •rack: Chassis number of the rack. •slot: Physical slot number of the modular services card or line card. •module: Module number. A physical layer interface module (PLIM) is always 0. Shared port adapters (SPAs) are referenced by their subslot number. •port: Physical port number of the T3 controller. •t1-num: T1 or E1 channel number. T1 channels range from 1 to 24; E1 channels range from 1 to 31. •channel-group-number: Time slot number. T1 time slots range from 1 to 24; E1 time slots range from 1 to 31. The channel-group-number is preceded by a colon and not a slash. For a complete list of all valid instances, use the question mark (?) online help function.
.subinterface	(Optional) Subinterface instance. Naming notation is .subinterface. The period in front of the subinterface value is required as part of the notation. Replace subinterface with the virtual interface number to be associated with the physical interface. Note For more information about the syntax for the router, use the question mark (?) online help function.
point-to-point	Interface functions as one endpoint of a point-to-point link.
l2transport	Interface functions as one endpoint on an Layer 2 link.

Defaults

No default behavior or values

Command Modes

Global configuration

Command History

Release	Modification
Release 3.3.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.4.0	No modification.
Release 3.5.0	The l2transport keyword was added to support Layer 2 configuration on serial interfaces.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Use the question mark (?) online help function following the serial keyword to view a list of all valid interface choices. To reference the serial interface on channel group 3 of T1 channel group 4 on port 2 of a SPA in subslot 1, use the following notation: interface serial 0/0/1/2/4:3.

Serial interfaces on channelized T3 can be deleted using the no channel-group command in T1 configuration mode. If there are nondefault serial parameters defined, you need to use the no interface serial command first to revert to the default configuration, and then delete the serial interface using the no channel-group command.

Task ID

Task ID	Operations
interface	read, write

Examples

The following example shows how to enter interface configuration mode for a serial interface in slot 6, subslot 2, port 4, T1 channel number 10 and channel group 8:

RP/0/0/CPU0:Router(config)# interface serial 0/6/2/4/10:8

RP/0/0/CPU0:Router(config-if)# 

The following example shows how to create a subinterface on a serial interface in slot 6, subslot 2, port 3 and enter subinterface configuration mode:

RP/0/0/CPU0:Router(config)# interface serial 0/6/2/3.1

RP/0/0/CPU0:Router(config-if)# 

Related Commands

Command	Description
channel-group	Configures a T1 channel group and enter s channel group configuration mode.
show interfaces	Displays statistics for all interfaces configured on the router or on a specific node.

keepalive (serial)

To set the keepalive timer for a specific serial interface, use the keepalive command in interface configuration mode. To reset the keepalive timer to the default of 10 seconds, use the no form of this command.

keepalive {seconds | disable}

no keepalive

Syntax Description

seconds	Number of seconds that define the keepalive interval. Default is 10 seconds.
disable	Turns off the keepalive timer.

Defaults

seconds = 10 seconds

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.0	No modification.
Release 3.2	This command was first supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

cHDLC keepalives require that the keepalive command is configured the same way on both ends of a single connection. The two connected routers have no way of negotiating the keepalive value because there is no way for one router to tell the other about its configured values. The keepalive value configured on each router (local or partner) sets the rate at which the Cisco IOS XR software sends packets. It also sets the rate at which the local end expects to receive incoming packets.

To set the keepalive value to the default value, use the keepalive command without specifying a value for the seconds argument.

If three keepalives are sent to the peer and no response is received from peer, then the link makes the transition to the down state.

Task ID

Task ID	Operations
hdlc	read, write

Examples

The following example shows how to configure keepalives for 3 seconds on serial interface 0/7/0/1:

RP/0/0/CPU0:router(config)# interface serial 0/7/0/1

RP/0/0/CPU0:router(config-if)# keepalive 3

Related Commands

Command	Description
show interfaces	Displays statistics for all interfaces configured on the router or on a specific node.

invert

To invert the data stream on a serial interface, use the invert command in serial configuration mode. To disable data inversion, use the no form of this command.

invert

no invert

Syntax Description

This command has no arguments or keywords.

Defaults

Data is not inverted

Command Modes

Serial configuration

Command History

Release	Modification
Release 3.3.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

To verify that data inversion is configured on the interface, use the show interfaces serial command.

Task ID

Task ID	Operations
hdlc	read, write

Examples

In the following example, data inversion is enabled on serial interface 0/3/0/0/0:10:

RP/0/0/CPU0:Router(config)# interface serial 0/3/0/0/0:10

RP/0/0/CPU0:Router(config-if)# serial

RP/0/0/CPU0:Router(config-if-serial)# invert

Related Commands

Command	Description
show interfaces	Displays statistics for all interfaces configured on the router or on a specific node.

pvc (serial)

To create a Frame Relay permanent virtual circuit (PVC) under a serial subinterface and enter Frame Relay virtual circuit configuration mode, use the pvc command in subinterface configuration mode. To remove a PVC from a subinterface, use the no form of this command.

pvc dlci

no pvc dlci

Syntax Description

dlci	DLCI number used to identify the PVC. Range is from 16 to 1007.

Defaults

No PVC is defined.

Command Modes

Subinterface configuration

Command History

Release	Modification
Release 3.4.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

The pvc command creates a PVC and attaches it to the specified DLCI.

The Cisco IOS XR software dynamically creates rate queues as necessary to satisfy the requests of the PVC commands.

When you issue the pvc command in global configuration mode, the CLI prompt changes to "config-fr-vc," indicating that you have entered the Frame Relay virtual circuit configuration submode.

In the following sample output, the question mark (?) online help function displays all the commands available under the Frame Relay virtual circuit configuration submode for the serial subinterface:

RP/0/0/CPU0:router# configure

RP/0/0/CPU0:router(config)# interface serial 0/3/2/0.1

RP/0/0/CPU0:router(config-subif)# pvc 20

RP/0/0/CPU0:router(config-fr-vc)# ?

  commit    Commit the configuration changes to running

  describe  Describe a command without taking real actions

  do        Run an exec command

  exit      Exit from this submode

  no        Negate a command or set its defaults

  show            Show contents of configuration

RP/0/0/CPU0:router(config-fr-vc)#

Task ID

Task ID	Operations
fr	read, write

Examples

The following example shows how to create a Frame Relay PVC on a serial subinterface, and enter Frame Relay virtual circuit configuration mode:

RP/0/0/CPU0:router# configure

RP/0/0/CPU0:router(config)# interface serial 0/6/0/1.1 point-to-point

RP/0/0/CPU0:router(config-if)# pvc 16

RP/0/0/CPU0:router(config-fr-vc)# 

scramble

To enable payload scrambling (encryption) on a serial interface, use the scramble command in interface configuration mode. To disable scrambling, use the no form of this command.

scramble

no scramble

Syntax Description

This command has no arguments or keywords.

Defaults

Scrambling is disabled

Command Modes

Interface configuration

Command History

Release	Modification
Release 3.3.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Scrambling is used to assist clock recovery on the receiving end. Scrambling is designed to randomize the pattern of 1s and 0s carried in the physical layer frame. Randomizing the digital bits can prevent continuous, nonvariable bit patterns—in other words, long strings of all 1s or all 0s. Several physical layer protocols rely on transitions between 1s and 0s to maintain clocking.

Scrambling can prevent some bit patterns from being mistakenly interpreted as alarms by switches placed between the Data Service Units (DSUs).

The local interface configuration must match the remote interface configuration. For example, if you enable scrambling on the local port, you must also do the same on the remote port.

To verify that scrambling is configured on the interface, use the show interfaces serial command.

Task ID

Task ID	Operations
hdlc	read, write

Examples

In the following example, scrambling is enabled on serial interface 0/3/0/0/0:10:

RP/0/0/CPU0:Router(config)# interface serial 0/3/0/0/0:10

RP/0/0/CPU0:Router(config-if)# serial

RP/0/0/CPU0:Router(config-if-serial)# scramble

Related Commands

Command	Description
show controllers t3	Displays information about the T3 controllers.

serial

To configure the serial parameters and enter serial configuration mode, use the serial command in interface configuration mode. To return to the default state of the serial interface, use the no form of this command.

serial

no serial

Syntax Description

This command has no arguments or keywords.

Defaults

No default behavior or values

Command Modes

Interface configuration

Command History

Release	Modification
Release 3.3.0	This command was introduced on the Cisco XR 12000 Series Router.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Serial interfaces are automatically created for unchannelized ports; for channelized ports, serial interfaces are created when you add T1/E1 channel groups.

Task ID

Task ID	Operations
hdlc	read, write

Examples

The following example shows how to enter serial configuration mode:

RP/0/0/CPU0:Router(config-if)# serial

RP/0/0/CPU0:Router(config-if-serial)#

transmit-delay (serial)

To specify a number of High-Level Data Link Control (HDLC) flag sequences to be inserted between the packets, use the transmit-delay command in serial configuration mode. To restore the default, use the no form of this command.

transmit-delay microseconds

no transmit-delay microseconds

Syntax Description

microseconds

Number of microseconds of minimum delay after sending a packet. Range is from 0 to 128. Default is 0 (disabled).

Defaults

microseconds = 0 (disabled)

Command Modes

Serial configuration

Command History

Releases	Modifications
Release 3.2	This command was introduced on the Cisco CRS-1 and the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Task ID

Task ID	Operations
hdlc	read, write

Examples

In the following example, a delay of 2 microseconds is specified on serial interface 0/3/0/0/0:0:

RP/0/0/CPU0:router# configure

RP/0/0/CPU0:router(config)# interface serial 0/3/0/0/0:0

RP/0/0/CPU0:router(config-if)# serial

RP/0/0/CPU0:router(config-if-serial)# transmit-delay 2

In the following example, the transmit delay on serial interface 0/3/0/0/0:0 is disabled:

RP/0/0/CPU0:router# configure

RP/0/0/CPU0:router(config)# interface serial 0/3/0/0/0:0

RP/0/0/CPU0:router(config-if)# serial

RP/0/0/CPU0:router(config-if-serial)# no transmit-delay

Related Commands

Command	Description
show interfaces	Displays statistics for all interfaces configured on the router or on a specific node.