Configuring Serial Interfaces

This module describes the configuration of serial interfaces.

Feature History for Configuring Serial Controller Interfaces

Release

Modification

Release 3.9.0

Support for serial interfaces was added on the Cisco ASR 9000 Series Router for the 2-Port Channelized OC-12c/DS0 SPA.

Release 4.0.0

Support for the following features and SPAs was added on the Cisco ASR 9000 Series Router:

  • Support for IPv4 multicast was added for serial interfaces. For more information about multicast configuration on an interface, see the Cisco ASR 9000 Series Aggregation Services Router Multicast Configuration Guide.

  • IPHC was added on the Cisco 2-Port Channelized OC-12c/DS0 SPA.

  • Support for the Cisco 1-Port Channelized OC-48/STM-16 SPA was introduced.

Release 4.0.1

Support for the following SPAs was added:

  • Cisco 1-Port Channelized OC-3/STM-1 SPA

  • Cisco 2-Port and 4-Port Clear Channel T3/E3 SPA

Release 4.1.0

Support for the following SPAs was added:

  • Cisco 4-Port Channelized T3/DS0 SPA

  • Cisco 8-Port Channelized T1/E1 SPA

Support for IPHC was added on the following SPAs:

  • Cisco 1-Port Channelized OC-3/STM-1 SPA

  • Cisco 4-Port Channelized T3/DS0 SPA

  • Cisco 8-Port Channelized T1/E1 SPA

  • Cisco 2-Port and 4-Port Clear Channel T3/E3 SPA

Prerequisites for Configuring Serial Interfaces

Before configuring serial interfaces, ensure that the following tasks and conditions are met:

  • You must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

  • You should have the following SIP and any one of the following SPAs installed on the Cisco ASR 9000 Series Router:

    • Cisco SIP 700 SPA Interface Processor

    • Cisco 1-Port Channelized OC-3/STM-1 SPA

    • Cisco 2-Port Channelized OC-12c/DS0 SPA

    • Cisco 1-Port Channelized OC-48/STM-16 SPA

    • Cisco 2-Port or 4-Port Clear Channel T3/E3 SPA

    • Cisco 4-Port Channelized T3/DS0 SPA

    • Cisco 8-Port Channelized T1/E1 SPA


Note

The Cisco 4-Port Channelized T3/DS0 SPA can run in clear channel mode, or it can be channelized into 28 T1 or 21 E1 controllers.

  • You should have configured the clear channel T3/E3 controller or channelized T3 to T1/E1 controller that is associated with the serial interface you want to configure, as described in the Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers module in this manual.


Note

On channelized T3 to T1/E1 controllers, serial interfaces are automatically created when users configure individual DS0 channel groups on the T1/E1 controllers.

Information About Configuring Serial Interfaces

To configure serial interfaces, study the following concepts:

On the Cisco ASR 9000 Series Router, a single serial interface carries data over a single interface using PPP, Cisco HDLC, or Frame Relay encapsulation.

High-Level Overview: Serial Interface Configuration on Channelized SPAs

provide a high-level overview of the tasks required to configure a T1 serial interface on the following SPAs and line cards.

  • Cisco 2-Port Channelized OC-12c/DS0 SPA

Table 1. Overview: Configuring a Serial Interface on a T1 DS0 Channel

Step

Task

Module

Section

1.

Configure the SONET controller parameters and STS stream for T3 mode.

Configuring Channelized SONET/SDH

Configuring SONET T3 and VT1.5-Mapped T1 Channels

2.

Configure the T3 controller parameters and set the mode to T1.

28 T1 controllers are automatically created.

Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers

Configuring a Channelized T3 Controller

3.

Create and configure DS0 channel groups on the T1 controllers.

Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers

Configuring a T1 Controller

4.

Configure the Serial interfaces that are associated channel groups you created in Step 2.

Configuring Serial Interfaces

How to Configure Serial Interfaces

provides a high-level overview of the tasks required to configure an E1 serial interface on the following SPAs and line cards.

  • 1-Port Channelized OC-3/STM-1 SPA

  • 2-Port Channelized OC-12c/DS0 SPA

Table 2. Overview: Configuring a Serial Interface on a E1 DS0 Channel

Step

Task

Module

Section

1.

Configure the SONET controller parameters and STS stream for T3 mode.

Configuring Channelized SONET/SDH

Configuring SONET T3 and VT1.5-Mapped T1 Channels

2.

Configure the T3 controller parameters and set the mode to E1.

21 E1 controllers are automatically created.

Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers

Configuring a Channelized T3 Controller

3.

Create and configure DS0 channel groups on the E1 controllers.

Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers

Configuring an E1 Controller

4.

Configure the Serial interfaces that are associated channel groups you created in Step 2.

Configuring Serial Interfaces

How to Configure Serial Interfaces

This table provides a high-level overview of the tasks required to configure a T3 serial interface on the 1-Port Channelized OC-48/STM-16 SPA

Table 3. Overview: Configuring a Serial Interface on a T3 Channel

Step

Task

Module

Section

1.

Configure the SONET controller parameters and STS stream.

Configuring Channelized SONET/SDH

Configuring a Clear Channel SONET Controller

2.

Configure the STS stream mode for T3 and configure the T3 controller parameters.

Configuring Channelized SONET/SDH

Configuring a Clear Channel SONET Controller for T3

3.

Configure the Serial interfaces.

Configuring Serial Interfaces

How to Configure Serial Interfaces

Cisco HDLC Encapsulation

Cisco High-Level Data Link Controller (HDLC) is the Cisco proprietary protocol for sending data over synchronous serial links using HDLC. Cisco HDLC also provides a simple control protocol called Serial Line Address Resolution Protocol (SLARP) to maintain serial link keepalives. HDLC is the default encapsulation type for serial interfaces under Cisco IOS XR software. Cisco HDLC is the default for data encapsulation at Layer 2 (data link) of the Open System Interconnection (OSI) stack for efficient packet delineation and error control.


Note

Cisco HDLC is the default encapsulation type for the serial interfaces.

Cisco HDLC uses keepalives to monitor the link state, as described in the “Keepalive Timer” section on page 553.


Note

Use the debug chdlc slarp packet command to display information about the Serial Line Address Resolution Protocol (SLARP) packets that are sent to the peer after the keepalive timer has been configured.

PPP Encapsulation

PPP is a standard protocol used to send data over synchronous serial links. PPP also provides a Link Control Protocol (LCP) for negotiating properties of the link. LCP uses echo requests and responses to monitor the continuing availability of the link.


Note

When an interface is configured with PPP encapsulation, a link is declared down, and full LCP negotiation is re-initiated after five ECHOREQ packets are sent without receiving an ECHOREP response.

PPP provides the following Network Control Protocols (NCPs) for negotiating properties of data protocols that will run on the link:

  • IP Control Protocol (IPCP) to negotiate IP properties

  • Multiprotocol Label Switching control processor (MPLSCP) to negotiate MPLS properties

  • Cisco Discovery Protocol control processor (CDPCP) to negotiate CDP properties

  • IPv6CP to negotiate IP Version 6 (IPv6) properties

  • Open Systems Interconnection control processor (OSICP) to negotiate OSI properties

PPP uses keepalives to monitor the link state, as described in the “Keepalive Timer” section on page 553.

PPP supports the following authentication protocols, which require a remote device to prove its identity before allowing data traffic to flow over a connection:

  • Challenge Handshake Authentication Protocol (CHAP)—CHAP authentication sends a challenge message to the remote device. The remote device encrypts the challenge value with a shared secret and returns the encrypted value and its name to the local router in a response message. The local router attempts to match the name of the remote device with an associated secret stored in the local username or remote security server database; it uses the stored secret to encrypt the original challenge and verify that the encrypted values match.

  • Microsoft Challenge Handshake Authentication Protocol (MS-CHAP)—MS-CHAP is the Microsoft version of CHAP. Like the standard version of CHAP, MS-CHAP is used for PPP authentication; in this case, authentication occurs between a personal computer using Microsoft Windows NT or Microsoft Windows 95 and a Cisco router or access server acting as a network access server.

  • Password Authentication Protocol (PAP)—PAP authentication requires the remote device to send a name and a password, which are checked against a matching entry in the local username database or in the remote security server database.


Note

For more information on enabling and configuring PPP authentication protocols, see the Configuring PPP module in this manual.

Use the ppp authentication command in interface configuration mode to enable CHAP, MS-CHAP, and PAP on a serial interface.


Note

Enabling or disabling PPP authentication does not effect the local router’s willingness to authenticate itself to the remote device.

Multilink PPP

Multilink Point-to-Point Protocol (MLPPP) is supported on these SPAs:

  • 1-Port Channelized OC-3/STM-1 SPA

  • 2-Port Channelized OC-12/DS0 SPA

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 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

For more information about configuring MLPPP on a serial interface, see the Configuring PPP module in this document.

Keepalive Timer

Cisco keepalives are useful for monitoring the link state. Periodic keepalives are sent to and received from the peer at a frequency determined by the value of the keepalive timer. If an acceptable keepalive response is not received from the peer, the link makes the transition to the down state. As soon as an acceptable keepalive response is obtained from the peer or if keepalives are disabled, the link makes the transition to the up state.


Note

The keepalive command applies to serial interfaces using HDLC or PPP encapsulation. It does not apply to serial interfaces using Frame Relay encapsulation.

For each encapsulation type, a certain number of keepalives ignored by a peer triggers the serial interface to transition to the down state. For HDLC encapsulation, three ignored keepalives causes the interface to be brought down. For PPP encapsulation, five ignored keepalives causes the interface to be brought down. ECHOREQ packets are sent out only when LCP negotiation is complete (for example, when LCP is open).


Note

Use the keepalive command in interface configuration mode to set the frequency at which LCP sends ECHOREQ packets to its peer. To restore the system to the default keepalive interval of 10 seconds, use the keepalive command with no argument. To disable keepalives, use the keepalive disable command. For both PPP and Cisco HDLC, a keepalive of 0 disables keepalives and is reported in the show running-config command output as keepalive disable .


Note

When LCP is running on the peer and receives an ECHOREQ packet, it responds with an echo reply (ECHOREP) packet, regardless of whether keepalives are enabled on the peer.

Keepalives are independent between the two peers. One peer end can have keepalives enabled; the other end can have them disabled. Even if keepalives are disabled locally, LCP still responds with ECHOREP packets to the ECHOREQ packets it receives. Similarly, LCP also works if the period of keepalives at each end is different.


Note

Use the debug chdlc slarp packet command and other Cisco HDLC debug commands to display information about the Serial Line Address Resolution Protocol (SLARP) packets that are sent to the peer after the keepalive timer has been configured.

Frame Relay Encapsulation

When Frame Relay encapsulation is enabled on a serial interface, the interface configuration is hierarchical and comprises the following elements:

  1. The serial main interface comprises the physical interface and port. If you are not using the serial interface to support Cisco HDLC and PPP encapsulated connections, then you must configure subinterfaces with permanent virtual circuits (PVCs) under the serial main interface. Frame Relay connections are supported on PVCs only.

  2. Serial subinterfaces are configured under the serial main interface. A serial subinterface does not actively carry traffic until you configure a PVC under the serial subinterface. Layer 3 configuration typically takes place on the subinterface.

  3. Point-to-point PVCs are configured under a serial subinterface. You cannot configure a PVC directly under a main interface. A single point-to-point PVC is allowed per subinterface. PVCs use a predefined circuit path and fail if the path is interrupted. PVCs remain active until the circuit is removed from either configuration. Connections on the serial PVC support Frame Relay encapsulation only.


Note

The administrative state of a parent interface drives the state of the subinterface and its PVC. When the administrative state of a parent interface or subinterface changes, so does the administrative state of any child PVC configured under that parent interface or subinterface.

To configure Frame Relay encapsulation on serial interfaces, use the encapsulation frame-relay command.

Frame Relay interfaces support two types of encapsulated frames:

  • Cisco (default)

  • IETF

Use the encap command in PVC configuration mode to configure Cisco or IETF encapsulation on a PVC. If the encapsulation type is not configured explicitly for a PVC, then that PVC inherits the encapsulation type from the main serial interface.


Note

Cisco encapsulation is required on serial main interfaces that are configured for MPLS. IETF encapsulation is not supported for MPLS.

Before you configure Frame Relay encapsulation on an interface, you must verify that all prior Layer 3 configuration is removed from that interface. For example, you must ensure that there is no IP address configured directly under the main interface; otherwise, any Frame Relay configuration done under the main interface will not be viable.

LMI on Frame Relay Interfaces

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. However, you can modify the default LMI type to be ANSI or Q.933, as described in the Modifying the Default Frame Relay Configuration on an Interface section of the Configuring Frame Relaymodule in this manual.

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.

Default Settings for Serial Interface Configurations

When an interface is enabled on a T3/E3 SPA, and no additional configuration commands are applied, the default interface settings shown in this table are present. These default settings can be changed by configuration.

Table 4. Serial Interface Default Settings

Parameter

Configuration File Entry

Default Settings

Keepalive

Note

 

The keepalive command applies to serial interfaces using HDLC or PPP encapsulation. It does not apply to serial interfaces using Frame Relay encapsulation.

keepalive [disable] 
no keepalive

keepalive 10 seconds

Encapsulation

encapsulation [hdlc | ppp | frame-relay [ietf]]

hdlc

Maximum transmission unit (MTU)

mtu bytes

1504 bytes

Cyclic redundancy check (CRC)

crc [16 | 32]

16

Data stream inversion on a serial interface

invert

Data stream is not inverted

Payload scrambling (encryption)

scramble

Scrambling is disabled.

Number of High-Level Data Link Control (HDLC) flag sequences to be inserted between the packets

transmit-delay

Default is 0 (disabled).

Note

Default settings do not appear in the output of the show running-config command.

Serial Interface Naming Notation

The naming notation for T1, E1, and DS0 interfaces on a channelized SPA is rack/slot/module/port/channel-num:channel-group-number , as shown in the following example: 

interface serial 0/0/1/2/4:3

If a subinterface and PVC are configured under the serial interface, then the router includes the subinterface number at the end of the serial interface address. In this case, the naming notation is rack/slot/module/port[/channel-num:channel-group-number] .subinterface, as shown in the following examples: 

interface serial 0/0/1/2.1
interface serial 0/0/1/2/4:3.1

Note

A slash between values is required as part of the notation.

The naming notation syntax for serial interfaces is as follows:

  • rack: Chassis number of the rack.

  • slot: Physical slot number of the modular services card or line card.

  • module: Module number. Shared port adapters (SPAs) are referenced by their subslot number.

  • port: Physical port number of the controller.

  • channel-num : T1 or E1 channel number. T1 channels range from 0 to 23; E1 channels range from 0 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.

  • subinterface : Subinterface number.

Use the question mark (?) online help function following the serial keyword to view a list of all valid interface choices.

IPHC Overview

IP header compression (IPHC) is based on the premise that most of the headers in the packets of a particular transmission remain constant throughout the flow. Only a few fields in the headers of related packets change during a flow.

IPHC compresses these headers so that the compressed header contains only the fields that change from packet to packet. All fields that remain the same from packet to packet are eliminated in the compressed headers. Full headers are sent between compressed headers.

Full headers are uncompressed headers that contain all the original header fields along with additional information (context ID) to identify the flow. The interval at which full headers are sent between compressed packets is configurable using the refresh max-period and refresh max-time commands.

IPHC contexts are used by the compressor (sender) and decompressor (receiver) of compressed packets to encode and decode the packets in a flow. A context is stored on the compressor and decompressor and is used in the delta calculation at both ends. The number of contexts allowed on a particular interface is configurable. The maximum size of the header that can be compressed is also configurable.

IPHC supports the compression and decompression of RTP and UDP traffic and the decompression of CN on TCP and CTCP traffic.

Users may choose one of the following types of compression formats:

  • Internet Engineering Task Force (IETF) standard format. 
Uses RFC2507 and RFC2508 compression schemes.

  • IPHC format.
Provides options similar to IETF.

This table shows the IPHC features, the values of the features, and their defaults:

IPHC Feature

Values

Defaults

TCP contexts

0 to 255

1

Non-TCP contexts

1 to 6000

16

Compression Format Options

IETF or IPHC

—

Feedback Messages

Enable or Disable

Enabled

Maximum Refresh Period Size

1 to 65535 packets

256

Maximum Refresh Time Period

0 to 255 seconds

5

Maximum Header Size

20 to 40 bytes

40

Real Time Protocol (RTP)

Enable or Disable

Enabled

Refresh RTP

Enable or Disable

Disable

Currently, only IPv4 unicast packets with UDP in the protocol field of the IP header are compressed.

IPHC is configured on an interface as follows:

  • Create an IPHC profile

  • Configure IPHC attributes in the profile

  • Attach the profile to an interface

IPHC profiles must contain the rtp command to enable Real Time Protocol (RTP) on the interface, or the profile is not enabled. The refresh rtp command must be used to enable the configured refresh settings for RTP packets. By default, refresh RTP is disabled and only the first packet in the flow is sent as a ‘full-header’ packet.

If some attributes, such as feedback messages, maximum refresh period size, maximum refresh time period, and maximum header size, are not configured in the profile, the default values for those attributes apply when the profile is enabled on the interface.

Currently, IPHC is supported only on serial interfaces with PPP encapsulation and on multilink with PPP encapsulation interfaces.

IPHC is typically configured between the Customer Edge (CE) and Provide Edge (PE) ends of an interface and must be configured at both ends of the interface to work. The PPP protocol negotiates the IPHC specific parameters between the two ends of the interface and settles on the lowest value configured between the two ends.

QoS and IPHC

An IPHC profile can be enabled on an interface so that the IPHC profile applies only to packets that match a Quality of Service (QoS) service policy. In this case, the QoS service-policy class attributes determine which packets are compressed. This allows users to fine tune IPHC with greater granularity.

Policy maps are attached to an interface using the service-policy command. IPHC action applies only to output service policies. IPHC is not supported on input service policies.

The user can configure IPHC using QoS as follows:

  • Create a QoS policy-map with the compress header ip action.

  • Attach the IPHC profile to the interface using the ipv4 iphc profile profile_name mode service-policy command.

  • Attach the QoS policy-map with compress header ip action using the service-policy output command.

See “IPHC on a Serial Interface with MLPPP/LFI and QoS Configuration: Example” section on page 586 for an example of how to configure IPHC using QoS.

For complete information on configuring QoS, refer to the Modular QoS Configuration Guide for Cisco ASR 9000 Series Routers.

How to Configure Serial Interfaces

After you have configured a channelized T3/E3 controller, as described in the Configuring Clear Channel T3/E3 Controllers and Channelized T3 and T1/E1 Controllers module in this document, you can configure the serial interfaces associated with that controller.

Bringing Up a Serial Interface

This task describes the commands used to bring up a serial interface.

Before you begin

  • The Cisco ASR 9000 Series Router must have the following SIP and at least one of the following SPAs installed and running Cisco IOS XR software:

  • SIP 700 SPA Interface Processor

  • 1-Port Channelized OC-3/STM-1 SPA

  • 2-Port Channelized OC-12c/DS0 SPA

  • 1-Port Channelized OC-48/STM-16 SPA

  • 4-Port Channelized T3/DS0 SPA

  • 2-Port and 4-Port Clear Channel T3/E3 SPA

  • 8-Port Channelized T1/E1 SPA

Restrictions

The configuration on both ends of the serial connection must match for the interface to be active.

SUMMARY STEPS

  1. show interfaces
  2. configure
  3. interface serial interface-path-id
  4. ipv4 address ip-address
  5. no shutdown
  6. end or commit
  7. exit
  8. exit
  9. Repeat Step 1 through Step 8 to bring up the interface at the other end of the connection.
  10. show ipv4 interface brief
  11. show interfaces serial interface-path-id

DETAILED STEPS

  Command or Action Purpose

Step 1

show interfaces

Example:


RP/0/RSP0/CPU0:router# show interfaces

(Optional) Displays configured interfaces.

  • Use this command to also confirm that the router recognizes the PLIM card.

Step 2

configure

Example:


RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 3

interface serial interface-path-id

Example:


RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/0

Specifies the serial interface name and notation rack/slot/module/port, and enters interface configuration mode.

Step 4

ipv4 address ip-address

Example:


RP/0/RSP0/CPU0:router(config-if)# ipv4 address 10.1.2.1 255.255.255.224

Assigns an IP address and subnet mask to the interface.

Note

 

  • Skip this step if you are configuring Frame Relay encapsulation on this interface. For Frame Relay, the IP address and subnet mask are configured under the subinterface.

Step 5

no shutdown

Example:


RP/0/RSP0/CPU0:router (config-if)# no shutdown

Removes the shutdown configuration.

Note

 

  • Removal of the shutdown configuration eliminates the forced administrative down on the interface, enabling it to move to an up or down state (assuming the parent SONET layer is not configured administratively down).

Step 6

end or commit

Example:


RP/0/RSP0/CPU0:router (config-if)# end

or 


RP/0/RSP0/CPU0:router(config-if)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 7

exit

Example:


RP/0/RSP0/CPU0:router (config-if)# exit

Exits interface configuration mode and enters global configuration mode.

Step 8

exit

Example:


RP/0/RSP0/CPU0:router (config)# exit

Exits global configuration mode and enters EXEC mode.

Step 9

Repeat Step 1 through Step 8 to bring up the interface at the other end of the connection.

Example:


RP/0/RSP0/CPU0:router# show interfaces


RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router (config)# interface serial 0/1/0/1
RP/0/RSP0/CPU0:router(config-if)# ipv4 address 10.1.2.2 255.255.255.224
RP/0/RSP0/CPU0:router (config-if)# no shutdown
RP/0/RSP0/CPU0:router (config-if)# commit
RP/0/RSP0/CPU0:router (config-if)# exit
RP/0/RSP0/CPU0:router (config)# exit

Note

 

  • The configuration on both ends of the serial connection must match.

Step 10

show ipv4 interface brief

Example:


RP/0/RSP0/CPU0:router # show ipv4 interface brief

Verifies that the interface is active and properly configured.

If you have brought up a serial interface properly, the “Status” field for that interface in the show ipv4 interface brief command output displays “Up.”

Step 11

show interfaces serial interface-path-id

Example:


RP/0/RSP0/CPU0:router# show interfaces serial 0/1/0/0

(Optional) Displays the interface configuration.

What to do next

To modify the default configuration of the serial interface you just brought up, see the “Configuring Optional Serial Interface Parameters” section on page 564.

Configuring Optional Serial Interface Parameters

This task describes the commands used to modify the default configuration on a serial interface.

Before you begin

Before you modify the default serial interface configuration, you must bring up the serial interface and remove the shutdown configuration, as described in the “Bringing Up a Serial Interface” section on page 559.

Restrictions

The configuration on both ends of the serial connection must match for the interface to be active.

SUMMARY STEPS

  1. configure
  2. interface serial interface-path-id
  3. encapsulation [hdlc | ppp | frame-relay [IETF]
  4. serial
  5. crc length
  6. invert
  7. scramble
  8. transmit-delay hdlc-flags
  9. end or commit
  10. exit
  11. exit
  12. exit
  13. show interfaces serial [interface-path-id]

DETAILED STEPS

  Command or Action Purpose

Step 1

configure

Example:


RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

interface serial interface-path-id

Example:


RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/0

Specifies the serial interface name and notation rack/slot/module/port, and enters interface configuration mode.

Step 3

encapsulation [hdlc | ppp | frame-relay [IETF]

Example:


RP/0/RSP0/CPU0:router(config-if)# encapsulation hdlc

(Optional) Configures the interface encapsulation parameters and details such as HDLC, PPP or Frame Relay.

Note

 

  • The default encapsulation is hdlc.

Step 4

serial

Example:


RP/0/RSP0/CPU0:router(config-if)# serial

(Optional) Enters serial submode to configure the serial parameters.

Step 5

crc length

Example:


RP/0/RSP0/CPU0:ios(config-if-serial)# crc 32

(Optional) Specifies the length of the cyclic redundancy check (CRC) for the interface. Enter the 16 keyword to specify 16-bit CRC mode, or enter the 32 keyword to specify 32-bit CRC mode.

Note

 

  • The default is CRC length is 16.

Step 6

invert

Example:


RP/0/RSP0/CPU0:ios(config-if-serial)# inverts

(Optional) Inverts the data stream.

Step 7

scramble

Example:


RP/0/RSP0/CPU0:ios(config-if-serial)# scramble

(Optional) Enables payload scrambling on the interface.

Note

 

  • Payload scrambling is disabled on the interface.

Step 8

transmit-delay hdlc-flags

Example:


RP/0/RSP0/CPU0:ios(config-if-serial)# transmit-delay 10

(Optional) Specifies a transmit delay on the interface. Values can be from 0 to 128.

Note

 

  • Transmit delay is disabled by default (the transmit delay is set to 0).

Step 9

end or commit

Example:


RP/0/RSP0/CPU0:router (config-if)# end

or 


RP/0/RSP0/CPU0:router(config-if)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 10

exit

Example:


RP/0/RSP0/CPU0:router(config-if-serial)# exit

Exits serial configuration mode.

Step 11

exit

Example:


RP/0/RSP0/CPU0:router (config-if)# exit

Exits interface configuration mode and enters global configuration mode.

Step 12

exit

Example:


RP/0/RSP0/CPU0:router (config)# exit

Exits global configuration mode and enters EXEC mode.

Step 13

show interfaces serial [interface-path-id]

Example:


RP/0/RSP0/CPU0:router# show interface serial 0/1/0/0

(Optional) Displays general information for the specified serial interface.

What to do next

  • To create a point-to-point Frame Relay subinterface with a PVC on the serial interface you just brought up, see the “Creating a Point-to-Point Serial Subinterface with a PVC” section on page 567.

  • To configure PPP authentication on serial interfaces with PPP encapsulation, see the “Configuring PPP on the Cisco ASR 9000 Series Router” module later in this manual.

  • To modify the default keepalive configuration, see the “Modifying the Keepalive Interval on Serial Interfaces” section on page 572.

  • To modify the default Frame Relay configuration on serial interfaces that have Frame Relay encapsulation enabled, see the “Modifying the Default Frame Relay Configuration on an Interface” section of the “Configuring Frame Relay on the Cisco ASR 9000 Series Router” module.

Creating a Point-to-Point Serial Subinterface with a PVC

The procedure in this section creates a point-to-point serial subinterface and configures a permanent virtual circuit (PVC) on that serial subinterface.


Note

Subinterface and PVC creation is supported on interfaces with Frame Relay encapsulation only.

Before you begin

Before you can create a subinterface on a serial interface, you must bring up the main serial interface with Frame Relay encapsulation, as described in the “Bringing Up a Serial Interface” section on page 559.

Restrictions

Only one PVC can be configured for each point-to-point serial subinterface.

SUMMARY STEPS

  1. configure
  2. interface serial interface-path-id .subinterface point-to-point
  3. ipv4 address ipv4_address/prefix
  4. pvc dlci
  5. end or commit
  6. Repeat Step 1 through Step 5 to bring up the serial subinterface and any associated PVC at the other end of the connection.

DETAILED STEPS

  Command or Action Purpose

Step 1

configure

Example:


RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

interface serial interface-path-id .subinterface point-to-point

Example:


RP/0/RSP0/CPU0:router (config)# interface serial 0/1/0/0.1

Enters serial subinterface configuration mode.

Step 3

ipv4 address ipv4_address/prefix

Example:


RP/0/RSP0/CPU0:router (config-subif)#ipv4 address 10.46.8.6/24

Assigns an IP address and subnet mask to the subinterface.

Step 4

pvc dlci

Example:


RP/0/RSP0/CPU0:router (config-subif)# pvc 20

Creates a serial permanent virtual circuit (PVC) and enters Frame Relay PVC configuration submode.

Replace dlci with a PVC identifier, in the range from 16 to 1007.

Note

 

  • Only one PVC is allowed per subinterface.

Step 5

end or commit

Example:


RP/0/RSP0/CPU0:router (config-subif)# end

or 


RP/0/RSP0/CPU0:router(config-subif)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 6

Repeat Step 1 through Step 5 to bring up the serial subinterface and any associated PVC at the other end of the connection.

Example:


RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router (config)# interface serial 0/1/0/1.1


RP/0/RSP0/CPU0:router (config-subif)#ipv4 address 10.46.8.5/24


RP/0/RSP0/CPU0:router (config-subif)# pvc 20
RP/0/RSP0/CPU0:router (config-fr-vc)# commit

Note

 

  • The DLCI (or PVC identifier) must match on both ends of the subinterface connection.

  • When assigning an IP address and subnet mask to the subinterface at the other end of the connection, keep in mind that the addresses at both ends of the connection must be in the same subnet.

What to do next

  • To configure optional PVC parameters, see the “Configuring Optional Serial Interface Parameters” section on page 564.

  • To modify the default Frame Relay configuration on serial interfaces that have Frame Relay encapsulation enabled, see the“Modifying the Default Frame Relay Configuration on an Interface” section of the “Configuring Frame Relay on the Cisco ASR 9000 Series Router” module.

  • To attach a Layer 3 QOS service policy to the PVC under the PVC submode, refer to the appropriate Cisco IOS XR software configuration guide.

Configuring Optional PVC Parameters

This task describes the commands you can use to modify the default configuration on a serial PVC.

For additional information about Frame Relay options, see the “Configuring Frame Relay on the Cisco ASR 9000 Series Router” module in the Cisco IOS XR Interface and Hardware Component Configuration Guide for the Cisco ASR 9000 Series Router.

Before you begin

Before you can modify the default PVC configuration, you must create the PVC on a serial subinterface, as described in the “Creating a Point-to-Point Serial Subinterface with a PVC” section on page 565.

Restrictions

  • The DLCI (or PVI identifier) must match on both ends of the PVC for the connection to be active.

  • To change the PVC DLCI, you must delete the PVC and then add it back with the new DLCI.

SUMMARY STEPS

  1. Configuring Optional PVC Parameters
  2. interface serial interface-path-id .subinterface
  3. pvc dlci
  4. encap [cisco | ietf]
  5. service-policy {input | output} policy-map
  6. end or commit
  7. Repeat Step 1 through Step 6 to bring up the serial subinterface and any associated PVC at the other end of the connection.
  8. show frame-relay pvc dlci-number
  9. show policy-map interface serial interface-path-id .subinterface {input | output} or show policy-map type qos interface serial interface-path-id .subinterface {input | output}

DETAILED STEPS

  Command or Action Purpose

Step 1

Configuring Optional PVC Parameters

Example:


RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2

interface serial interface-path-id .subinterface

Example:


RP/0/RSP0/CPU0:router (config)# interface serial 0/1/0/0.1

Enters serial subinterface configuration mode.

Step 3

pvc dlci

Example:


RP/0/RSP0/CPU0:router (config-subif)# pvc 20

Enters subinterface configuration mode for the PVC.

Step 4

encap [cisco | ietf]

Example:


RP/0/RSP0/CPU0:router (config-fr-vc)# encap ietf

(Optional) Configures the encapsulation for a Frame Relay PVC.

Note

 

  • If the encapsulation type is not configured explicitly for a PVC, then that PVC inherits the encapsulation type from the main serial interface.

Step 5

service-policy {input | output} policy-map

Example:


RP/0/RSP0/CPU0:router (config-fr-vc)# service-policy output policy1

Attaches a policy map to an input subinterface or output subinterface. Once attached, the policy map is used as the service policy for the subinterface.

Step 6

end or commit

Example:


RP/0/RSP0/CPU0:router (config-fr-vc)# end

or 


RP/0/RSP0/CPU0:router(config-fr-vc)# commit

Saves configuration changes.

  • When you issue the end command, the system prompts you to commit changes: 

    
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

    - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

    - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

    - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

  • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

Step 7

Repeat Step 1 through Step 6 to bring up the serial subinterface and any associated PVC at the other end of the connection.

Example:


RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router (config)# interface serial 0/1/0/1.1


RP/0/RSP0/CPU0:router (config-subif)# pvc 20


RP/0/RSP0/CPU0:router (config-fr-vc)# encap cisco
RP/0/RSP0/CPU0:router (config-fr-vc)# commit

Note

 

  • The configuration on both ends of the subinterface connection must match.

Step 8

show frame-relay pvc dlci-number

Example:


RP/0/RSP0/CPU0:router# show frame-relay pvc 20

(Optional) Verifies the configuration of specified serial interface.

Step 9

show policy-map interface serial interface-path-id .subinterface {input | output} or show policy-map type qos interface serial interface-path-id .subinterface {input | output}

Example:


RP/0/RSP0/CPU0:router# show policy-map interface serial 0/1/0/0.1 output

or 


RP/0/RSP0/CPU0:router# show policy-map type qos interface serial 0/1/0/0.1 output

(Optional) Displays the statistics and the configurations of the input and output policies that are attached to a subinterface.

What to do next

To modify the default Frame Relay configuration on serial interfaces that have Frame Relay encapsulation enabled, see the “Modifying the Default Frame Relay Configuration on an Interface” section of the “Configuring Frame Relay on the Cisco ASR 9000 Series Router” module in this manual.

Modifying the Keepalive Interval on Serial Interfaces

Perform this task to modify the keepalive interval on serial interfaces that have Cisco HDLC or PPP encapsulation enabled.


Note

When you enable Cisco HDLC or PPP encapsulation on a serial interface, the default keepalive interval is 10 seconds. Use this procedure to modify that default keepalive interval.

Cisco HDLC is enabled by default on serial interfaces.

Before you begin

Before modifying the keepalive timer configuration, ensure that Cisco HDLC or PPP encapsulation is enabled on the interface. Use the encapsulation command to enable Cisco HDLC or PPP encapsulation on the interface, as described in the “Configuring Optional Serial Interface Parameters” section on page 562.

Restrictions

    SUMMARY STEPS

    1. configure
    2. interface serial interface-path-id
    3. keepalive {seconds | disable} or no keepalive
    4. end or commit
    5. show interfaces serial interface-path-id

    DETAILED STEPS

      Command or Action Purpose

    Step 1

    configure

    Example:

    
RP/0/RSP0/CPU0:router# configure

    Enters global configuration mode.

    Step 2

    interface serial interface-path-id

    Example:

    
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/0

    Specifies the serial interface name and notation rack/slot/module/port and enters interface configuration mode.

    Step 3

    keepalive {seconds | disable} or no keepalive

    Example:

    
RP/0/RSP0/CPU0:router(config-if)# keepalive 3

    or 

    
RP/0/RSP0/CPU0:router(config-if)# no keepalive

    Specifies the number of seconds between keepalive messages.

    • Use the keepalive disable command, the no keepalive , or the keepalive command with an argument of 0 to disable the keepalive feature.

    • The range is from 1 to 30 seconds. The default is 10 seconds.

    • If keepalives are configured on an interface, use the no keepalive command to disable the keepalive feature before configuring Frame Relay encapsulation on that interface.

    Step 4

    end or commit

    Example:

    
RP/0/RSP0/CPU0:router(config-if)# end

    or 

    
RP/0/RSP0/CPU0:router(config-if)# commit

    Saves configuration changes.

    • When you issue the end command, the system prompts you to commit changes: 

      
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

      - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

      - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

      - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

    • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

    Step 5

    show interfaces serial interface-path-id

    Example:

    
RP/0/RSP0/CPU0:router# show interfaces serial 0/1/0/0

    (Optional) Verifies the interface configuration.

    Configuring IPHC

    This section contains the following step procedures:

    Prerequisites for Configuring IPHC

    IP header compression (IPHC) is supported on the following cards:

    • SIP 700 SPA Interface Processor

    • Cisco 2-Port Channelized OC-12c/DS0 SPA

    • Cisco 1-Port Channelized OC-3/STM-1 SPA

    • Cisco 4-Port Channelized T3/DS0 SPA

    • Cisco 8-Port Channelized T1/E1 SPA

    • Cisco 2-Port and 4-Port Clear Channel T3/E3 SPA

    Configuring an IPHC Profile

    This section describes how to create and configure an IP header compression (IPHC) profile. This procedure is for TCP and non-TCP compression.

    SUMMARY STEPS

    1. configure
    2. iphc profile profile-name type {cisco | ietf | iphc}
    3. tcp compression
    4. tcp context absolute number-of-contexts
    5. non-tcp compression
    6. non-tcp context absolute number-of-contexts
    7. rtp
    8. refresh max-period {max-number | infinite}
    9. refresh max-time {max-time | infinite}
    10. refresh rtp
    11. feedback disable
    12. max-header number-of-bytes
    13. end or commit

    DETAILED STEPS

      Command or Action Purpose

    Step 1

    configure

    Example:
    
RP/0/RSP0/CPU0:router# configure

    Enters global configuration mode.

    Step 2

    iphc profile profile-name type {cisco | ietf | iphc}

    Example:
    
RP/0/RSP0/CPU0:router(config)# iphc profile Profile_1 type iphc

    Creates an IPHC profile, sets the compression format type, and enters the IPHC profile configuration mode.

    Step 3

    tcp compression

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# tcp compression

    Enables TCP compression in an IPHC profile.

    Step 4

    tcp context absolute number-of-contexts

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# tcp context absolute 255

    Configures the maximum number of TCP contexts that are allowed for IPHC on a line card.

    Step 5

    non-tcp compression

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# non-tcp compression

    Enables non-TCP compression in an IPHC profile.

    Step 6

    non-tcp context absolute number-of-contexts

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# non-tcp context absolute 255

    Configures the maximum number of non-TCP contexts that are allowed for IPHC on a line card.

    Step 7

    rtp

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# rtp

    Configures Real Time Protocol (RTP) on the interface.

    Step 8

    refresh max-period {max-number | infinite}

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# refresh max-period 50

    Configures the maximum number of compressed IP header packets that are exchanged on a link before the IPHC context is refreshed.

    Step 9

    refresh max-time {max-time | infinite}

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# refresh max-time 10

    Configures the maximum time between context refreshes.

    Step 10

    refresh rtp

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# refresh rtp

    Enables the configured context refresh settings for RTP packets.

    Step 11

    feedback disable

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# feedback disable

    Disables the IPHC context status feedback messages on an interface.

    Step 12

    max-header number-of-bytes

    Example:
    
RP/0/RSP0/CPU0:router(config-iphc-profile)# max-header 20

    Configures the maximum size (in bytes) of a compressed IP header.

    Step 13

    end or commit

    Example:
    
RP/0/RSP0/CPU0:router(config-if)# end

    or 

    
RP/0/RSP0/CPU0:router(config-if)# commit

    Saves configuration changes.

    • When you issue the end command, the system prompts you to commit changes: 

      
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

      - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

      - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

      - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

    • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

    Enabling an IPHC Profile on an Interface

    This section describes how to enable an IP header compression (IPHC) profile on an interface by attaching the profile directly to the interface.

    SUMMARY STEPS

    1. configure
    2. interface type interface-path-id
    3. encapsulation {hdlc | ppp | frame-relay | mfr}
    4. ipv4 iphc profile profile-name [mode service-policy]
    5. service policy output service-policy-name
    6. end or commit

    DETAILED STEPS

      Command or Action Purpose

    Step 1

    configure

    Example:
    
RP/0/RSP0/CPU0:router# configure

    Enters global configuration mode.

    Step 2

    interface type interface-path-id

    Example:
    
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/1

    Specifies the interface.

    Note

     

    • Use the show interfaces command to see a list of all interfaces currently configured on the router.

    For more information about the syntax for the router, use the question mark (? ) online help function.

    Step 3

    encapsulation {hdlc | ppp | frame-relay | mfr}

    Example:
    
RP/0/RSP0/CPU0:router(config-if)# encapsulation ppp

    Specifies Layer 2 encapsulation for the interface.

    Step 4

    ipv4 iphc profile profile-name [mode service-policy]

    Example:
    
RP/0/RSP0/CPU0:router(config-if)# ipv4 iphc profile Profile_1
or
RP/0/RSP0/CPU0:router(config-if)# ipv4 iphc profile Profile_1 mode service-policy

    Attaches an IPHC profile to the interface:

    • profile-name —Text name of the IPHC profile to attach to the interface.

    • mode service-policy —Specifies that the IPHC profile applies only to a QoS service policy.

    Step 5

    service policy output service-policy-name

    Example:
    
RP/0/RSP0/CPU0:router(config-if)# service policy input | output | type service-policy-name

    (Optional) Specifies the name of the QoS service policy to which the IPHC profile applies. Only output service policies are allowed.

    Used only when mode service-policy is specified in Configuring an IPHC Profile procedure.

    Step 6

    end or commit

    Example:
    
RP/0/RSP0/CPU0:router(config-if)# end

    or 

    
RP/0/RSP0/CPU0:router(config-if)# commit

    Saves configuration changes.

    • When you issue the end command, the system prompts you to commit changes: 

      
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:

      - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

      - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

      - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

    • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

    Configuration Examples for Serial Interfaces

    This section provides the following configuration examples:

    Bringing Up and Configuring a Serial Interface with Cisco HDLC Encapsulation: Example

    The following example shows how to bring up a basic serial interface with Cisco HDLC encapsulation: 

    
RP/0/RSP0/CPU0:Router#config
RP/0/RSP0/CPU0:Router(config)# interface serial 0/3/0/0/0:0
RP/0/RSP0/CPU0:Router(config-if)# ipv4 address 192.0.2.2 255.255.255.252
RP/0/RSP0/CPU0:Router(config-if)# no shutdown
RP/0/RSP0/CPU0:router(config-if)# end
Uncommitted changes found, commit them? [yes]: yes

    The following example shows how to configure the interval between keepalive messages to be 10 seconds: 

    
RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# interface serial 0/3/0/0/0:0
RP/0/RSP0/CPU0:router(config-if)# keepalive 10
RP/0/RSP0/CPU0:router(config-if)# commit

    The following example shows how to modify the optional serial interface parameters: 

    
RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# interface serial 0/3/0/0/0:0
RP/0/RSP0/CPU0:Router(config-if)# serial
RP/0/RSP0/CPU0:Router(config-if-serial)# crc 16
RP/0/RSP0/CPU0:Router(config-if-serial)# invert
RP/0/RSP0/CPU0:Router(config-if-serial)# scramble
RP/0/RSP0/CPU0:Router(config-if-serial)# transmit-delay 3
RP/0/RSP0/CPU0:Router(config-if-serial)# commit

    The following is sample output from the show interfaces serial command: 

    
RP/0/RSP0/CPU0:Router# show interfaces serial 0/0/3/0/5:23 
Serial0/0/3/0/5:23 is down, line protocol is down
  Hardware is Serial network interface(s)
  Internet address is Unknown
  MTU 1504 bytes, BW 64 Kbit
     reliability 143/255, txload 1/255, rxload 1/255
  Encapsulation HDLC, crc 16,  loopback not set, keepalive set (10 sec)
  Last clearing of "show interface" counters 18:11:15
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     2764 packets input, 2816 bytes, 3046 total input drops
     0 drops for unrecognized upper-level protocol
     Received 0 broadcast packets, 0 multicast packets
              0 runts, 0 giants, 0 throttles, 0 parity
     3046 input errors, 1 CRC, 0 frame, 0 overrun, 2764 ignored, 281 abort
     2764 packets output, 60804 bytes, 0 total output drops
     Output 0 broadcast packets, 0 multicast packets
     0 output errors, 0 underruns, 0 applique, 0 resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

    Configuring a Serial Interface with Frame Relay Encapsulation: Example

    The following example shows how to create a serial interface on a SPA with Frame Relay encapsulation and a serial subinterface with a PVC on router 1: 

    
RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/0 
RP/0/RSP0/CPU0:router(config-if)# encapsulation frame-relay 
RP/0/RSP0/CPU0:router(config-if)#frame-relay intf-type dce 
RP/0/RSP0/CPU0:router(config-if)# no shutdown 
RP/0/RSP0/CPU0:router(config-if)# end 
Uncommitted changes found, commit them? [yes]: yes 

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/0.1  point-to-point 
RP/0/RSP0/CPU0:router (config-subif)#ipv4 address 10.20.3.1/24 

    
RP/0/RSP0/CPU0:router (config-subif)# pvc 16

    
RP/0/RSP0/CPU0:router (config-fr-vc)# encapsulation ietf

    
RP/0/RSP0/CPU0:router (config-fr-vc)# commit

    
RP/0/RSP0/CPU0:router(config-fr-vc)# exit

    
RP/0/RSP0/CPU0:router(config-subif)# exit

    
RP/0/RSP0/CPU0:router(config)# exit

    
RP/0/RSP0/CPU0:router# show interface serial 0/1/0/0
Wed Oct  8 04:14:39.946 PST DST
Serial0/1/0/0 is up, line protocol is up
  Interface state transitions: 5
  Hardware is Serial network interface(s)
  Internet address is 10.20.3.1/24
  MTU 4474 bytes, BW 44210 Kbit
     reliability 255/255, txload 0/255, rxload 0/255
  Encapsulation FRAME-RELAY, crc 16,
  Scrambling is disabled, Invert data is disabled
  LMI enq sent  0, LMI stat recvd 0, LMI upd recvd 0
  LMI enq recvd 880, LMI stat sent  880, LMI upd sent  0 , DCE LMI up
  LMI DLCI 1023  LMI type is CISCO  frame relay DCE
  Last clearing of "show interface" counters 02:23:04
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     858 packets input, 11154 bytes, 0 total input drops
     0 drops for unrecognized upper-level protocol
     Received 0 runts, 0 giants, 0 throttles, 0 parity
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     858 packets output, 12226 bytes, 0 total output drops
     0 output errors, 0 underruns, 0 applique, 0 resets
     0 output buffer failures, 0 output buffers swapped out

    The following example shows how to create a serial interface on a SPA with Frame Relay encapsulation and a serial subinterface with a PVC on router 2, which is connected to router 1: 

    
RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/1 
RP/0/RSP0/CPU0:router(config-if)# encapsulation frame-relay 
RP/0/RSP0/CPU0:router(config-if)# no shutdown 
RP/0/RSP0/CPU0:router(config-if)# end 
Uncommitted changes found, commit them? [yes]: yes 

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface serial 0/1/0/1.1  point-to-point 
RP/0/RSP0/CPU0:router (config-subif)#ipv4 address 10.20.3.2/24 

    
RP/0/RSP0/CPU0:router (config-subif)# pvc 16

    
RP/0/RSP0/CPU0:router (config-fr-vc)# encapsulation ietf

    
RP/0/RSP0/CPU0:router (config-fr-vc)# commit

    
RP/0/RSP0/CPU0:router(config-fr-vc)# exit

    
RP/0/RSP0/CPU0:router(config-subif)# exit

    
RP/0/RSP0/CPU0:router(config)# exit

    
RP/0/RSP0/CPU0:router# show interface serial 0/1/0/1
Wed Oct  8 04:13:45.046 PST DST
Serial0/1/0/1 is up, line protocol is up
  Interface state transitions: 7
  Hardware is Serial network interface(s)
  Internet address is Unknown
  MTU 4474 bytes, BW 44210 Kbit
     reliability 255/255, txload 0/255, rxload 0/255
  Encapsulation FRAME-RELAY, crc 16,
  Scrambling is disabled, Invert data is disabled
  LMI enq sent  1110, LMI stat recvd 875, LMI upd recvd 0, DTE LMI up
  LMI enq recvd 0, LMI stat sent  0, LMI upd sent  0
  LMI DLCI 1023  LMI type is CISCO  frame relay DTE
  Last clearing of "show interface" counters 02:22:09
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     853 packets input, 12153 bytes, 0 total input drops
     0 drops for unrecognized upper-level protocol
     Received 0 runts, 0 giants, 0 throttles, 0 parity
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     853 packets output, 11089 bytes, 0 total output drops
     0 output errors, 0 underruns, 0 applique, 0 resets
     0 output buffer failures, 0 output buffers swapped out

    Configuring a Serial Interface with PPP Encapsulation: Example

    The following example shows how to create and configure a serial interface with PPP encapsulation: 

    
RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface serial 0/3/0/0/0:0 
RP/0/RSP0/CPU0:router(config-if)# ipv4 address 172.18.189.38 255.255.255.224 
RP/0/RSP0/CPU0:router(config-if)# encapsulation ppp 
RP/0/RSP0/CPU0:router(config-if)# no shutdown 
RP/0/RSP0/CPU0:router(config-if)# ppp authentication chap MIS-access 
RP/0/RSP0/CPU0:router(config-if)# end 
Uncommitted changes found, commit them? [yes]: yes

    The following example shows how to configure serial interface 0/3/0/0/0:0 to allow two additional retries after an initial authentication failure (for a total of three failed authentication attempts): 

    
RP/0/RSP0/CPU0:router# configuration 
RP/0/RSP0/CPU0:router(config)# interface serial 0/3/0/0/0:0 
RP/0/RSP0/CPU0:router(config-if)# encapsulation ppp 
RP/0/RSP0/CPU0:router(config-if)# ppp authentication chap 
RP/0/RSP0/CPU0:router(config-if)# ppp max-bad-auth 3 
RP/0/RSP0/CPU0:router(config-if)# end 
Uncommitted changes found, commit them? [yes]: yes

    IPHC Configuration: Examples

    This section provides the following examples:

    IPHC Profile Configuration: Example

    The following example shows how to configure an IPHC Profile: 

    config 


  iphc profile Profile_1 type iphc  
    tcp compression 
    tcp context absolute 255 
    non-tcp compression
    non-tcp context absolute 255 
    rtp
    refresh max-period 50 
	refresh max-time 10 
	refresh rtp 
	feedback disable 
    max-header 20 
commit

    IPHC on a Serial Interface Configuration: Examples

    Example 1

    The following example shows how to enable an IP header compression (IPHC) profile on a serial interface by attaching the profile directly to the interface: 

    config 
  interface serial 0/1/0/1 
    encapsulation ppp
    ipv4 iphc profile Profile_1 
commit
    Example 2

    The following example shows how to enable an IP header compression (IPHC) profile on an interface by specifying a QoS service policy that contains an IPHC profile: 

    config 
  interface serial 0/1/0/1:1 
    encapsulation ppp
    ipv4 iphc profile Profile_2 mode service-policy 
    service-policy output ip_header_compression_policy_map 
commit

    IPHC on Multilink Configuration: Example

    The following example shows how to configure an IP header compression (IPHC) on a multilink interface: 

    config 
  interface multilink 0/4/3/0/4 
    ipv4 address 10.10.10.10 
    encapsulation ppp
    ipv4 iphc profile Profile_1 
    commit 
  interface serial 0/1/0/1:1 
    encapsulation ppp
    multilink group 4
    commit

    IPHC on a Serial Interface with MLPPP/LFI and QoS Configuration: Example

    The following example shows how to configure IP header compression (IPHC) on a serial interface with LFI and by specifying a QoS service policy that contains an IPHC profile: 

    config 
  interface multilink 0/4/3/0/4 
    ipv4 address 10.10.10.10 
      multilink 
        fragment-size 128
        interleave
    ipv4 iphc profile Profile_2 mode service-policy 
    service-policy output SP_2 
    commit
  interface serial 0/1/0/1:2 
    encapsulation ppp
    multilink group 4
    commit