Cisco ASR 9000 Series Instruction sheet

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Configuring Serial Interfaces on the
Cisco ASR 9000 Series Router
This module describes the configuration of serial interfaces on the Cisco ASR 9000 Series Router.
Before you configure a serial interface, you must configure the clear channel T3/E3 controller or
channelized T1/E1controller (DS0 channel) that is associated with that interface.
Feature History for Configuring Serial Controller Interfaces
Release Modification
Release 3.3.0 This feature was introduced on the Cisco XR 12000 Series Router.
Support was added on the Cisco XR 12000 Series Router for the following
hardware:
•Cisco XR 12000 SIP-401
•Cisco XR 12000 SIP-501
•Cisco XR 12000 SIP-601
Support was added on the Cisco XR 12000 Series Router for the following
SPAs:
•Cisco 2-Port and 4-Port Channelized T3/DS0 SPA
•Cisco 2-Port and 4-Port T3/E3 Serial SPA
Release 3.4.0 Support for the following features was introduced:
•Subinterfaces with permanent virtual circuits (PVCs)
•Frame Relay encapsulation on serial main interfaces and PVCs on the
following hardware:
– Cisco 8-port Channelized T1/E1 SPA
– Cisco 2-Port and 4-Port Channelized T3/DS0 SPA
– Cisco 2-Port and 4-Port T3/E3 Serial SPA
– Cisco 1-Port Channelized OC-3 SPA
– Cisco 1-Port Channelized OC-12 SPA
– Cisco 1-Port Channelized OC-48 SPA
– Cisco 1-Port Channelized OC-12/STM-4 ISE Line Card

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Release 3.4.1 This feature was introduced on the Cisco CRS-1 Router.
Support was added on the Cisco CRS-1 Router for the following hardware:
•Cisco CRS-1 SIP-800
•Cisco 2-Port and 4-Port Clear Channel T3/E3 SPA
Multilink PPP was supported on serial interfaces on the
Cisco XR 12000 Series Router.
Release 3.5.0 Support was added on the Cisco XR 12000 Series Router for the following
SPAs:
•Cisco 1-Port Channelized OC-12/DS0 SPA
•Cisco 1-Port Channelized OC-48/STM-16 SPA
Release 3.7.0 Support was added on the Cisco XR 12000 Series Router for the 1-Port
Channelized OC-48/DS3 Line Card.
Release 3.8.0 Support was added on the Cisco XR 12000 Series Router for quality of
service (QoS) on Layer 2 subinterfaces and the following line cards:
•Cisco 1-Port Channelized OC-12/DS0 Line Card
•Cisco 4-Port Channelized OC-12/DS3 Line Card
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 4.0.0 Support for fragmentation counters using the fragment-counter command
was added for 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

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Contents
•Prerequisites for Configuring Serial Interfaces, page 501
•Information About Configuring Serial Interfaces, page 502
•How to Configure Serial Interfaces, page 514
•Configuration Examples for Serial Interfaces, page 542
•Additional References, page 547
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 have installed a 2-Port or 4-Port Clear Channel T3/E3 SPA.
•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
•Your hardware must support T3/E3 or T1/E1 controllers and serial interfaces.
The following hardware supports T3/E3 controllers and serial interfaces:
– Cisco 2-Port and 4-Port Clear Channel T3/E3 SPAs
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

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– Cisco 2-Port and 4-Port Channelized T3 SPAs
– Cisco 4-Port Channelized OC-12/DS3 line cards
– Cisco 1-Port Channelized OC-48/STM-16 SPA and line cards
The following hardware supports T1/E1 controllers and DS0 channels:
– Cisco 2-Port and 4-Port Channelized T3 SPAs
– Cisco 4-Port Channelized OC-12/DS3 line cards
– Cisco 1-Port Channelized OC-12/DS0 SPAs and line cards
– Cisco 1-Port Channelized OC-48/DS3 SPAs and line cards
– Cisco 1-Port Channelized OC3/STM-1 SPA
– Cisco 8-Port Channelized T1/E1 SPA
The following hardware supports serial interfaces:
– Cisco 2-Port and 4-Port Clear Channel T3/E3 SPAs
– Cisco 2-Port and 4-Port Channelized T3 SPAs
– Cisco 4-Port Channelized OC-12/DS3 line cards
– Cisco 1-Port Channelized OC-12/DS0 SPAs and line cards
– Cisco 1-Port Channelized OC-48/DS3 SPAs and line cards
– Cisco 1-Port Channelized OC3/STM-1 SPA
– Cisco 8-Port Channelized T1/E1 SPA
Note The Cisco 2-Port and 4-Port Channelized T3 SPAs can run in clear channel mode, or they can be
channelized into 28 T1 or 21 E1 controllers.
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 and Channelized T3 and T1/E1 Controllers on the
Cisco ASR 9000 Series Router” 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:
•High-Level Overview: Serial Interface Configuration on Clear-Channel SPAs, page 503
•High-Level Overview: Serial Interface Configuration on Channelized SPAs, page 504
•Cisco HDLC Encapsulation, page 506

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•PPP Encapsulation, page 506
•Keepalive Timer, page 508
•Frame Relay Encapsulation, page 509
•Layer 2 Tunnel Protocol Version 3-Based Layer 2 VPN on Frame Relay, page 510
•Default Settings for Serial Interface Configurations, page 511
•Serial Interface Naming Notation, page 511
•IPHC Overview, page 512
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 Clear-Channel SPAs
Table 14 provides a high-level overview of the tasks required to configure a T3 serial interface on the
Cisco 2-Port and 4-Port Clear Channel T3/E3 SPA.
Table 15 provides a high-level overview of the tasks required to configure an E3 serial interface on a
2-Port and 4-Port Clear Channel T3/E3 SPA.
Table 14 Overview: Configuring a T3 Serial Interface on a Clear Channel SPA
Step Task Module Section
1. Use the hw-module subslot
command to set serial mode for the
SPA to be T3, if necessary.
Note By default, the 2-Port and
4-Port Clear Channel T3/E3
SPA is set to run in T3 mode.
“Configuring Clear Channel T3/E3 and
Channelized T3 and T1/E1 Controllers
on the Cisco ASR 9000 Series Router”
Setting the Card Type
2. Configure the T3 controller. “Configuring Clear Channel T3/E3 and
Channelized T3 and T1/E1 Controllers
on the Cisco ASR 9000 Series Router”
Setting the Card Type
3. Configure the serial interface that is
associated with the T3 controller
you configured in Step 2.
“Configuring Serial Interfaces on the
Cisco ASR 9000 Series Router”
“How to Configure Serial Interfaces”
Table 15 Overview: Configuring an E3 Serial Interface on a Clear Channel SPA
Step Task Module Section
1. Use the hw-module subslot
command to set serial mode for the
SPA to be E3.
“Configuring Clear Channel T3/E3 and
Channelized T3 and T1/E1 Controllers
on the Cisco ASR 9000 Series Router”
Setting the Card Type
2. Configure the E3 controller. “Configuring Clear Channel T3/E3 and
Channelized T3 and T1/E1 Controllers
on the Cisco ASR 9000 Series Router”
Setting the Card Type
3. Configure the serial interface that is
associated with the E3 controller
you configured in Step 2.
Configuring Serial Interfaces on the
Cisco ASR 9000 Series Router
How to Configure Serial Interfaces

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High-Level Overview: Serial Interface Configuration on Channelized SPAs
Table 16Table 17 provides a high-level overview of the tasks required to configure a T1 serial interface
on the following SPAs and line cards.
•Cisco 2-Port and 4-Port Channelized T3 SPA
•Cisco 4-Port Channelized OC-12/DS3 line cards
•Cisco 1-Port Channelized OC-12/DS0 SPAs and line cards
•Cisco 1-Port Channelized OC-48/STM-16 SPA and line cards
•Cisco 2-Port Channelized OC-12c/DS0 SPA
Table 16 Overview: Configuring a Serial Interface on a T1 DS0 Channel
Step Task Module Section
1. Configure the T3 controller
parameters and set the SPA mode to
be T3.
28 T1 controllers are automatically
created.
“Configuring Clear Channel
T3/E3 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Setting the Card Type
Configuring a Channelized T3
Controller
2. Create and configure DS0 channel
groups on the T1 controllers.
“Configuring Clear Channel
T3/E3 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Configuring a T1 Controller
3. Configure the Serial interfaces that
are associated channel groups you
created in Step 2.
“Configuring Serial Interfaces on
the
Cisco ASR 9000 Series Router”
How to Configure Serial Interfaces
Table 17 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 on the
Cisco ASR 9000 Series Router”
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 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Configuring a Channelized T3
Controller
3. Create and configure DS0 channel
groups on the T1 controllers.
“Configuring Clear Channel
T3/E3 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Configuring a T1 Controller
4. Configure the Serial interfaces that
are associated channel groups you
created in Step 2.
“Configuring Serial Interfaces on
the
Cisco ASR 9000 Series Router”
How to Configure Serial Interfaces

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Table 18 provides a high-level overview of the tasks required to configure an E1 serial interface on the
following SPAs and line cards.
•2-Port and 4-Port Channelized T3 SPA
•4-Port Channelized OC-12/DS3 line cards
•1-Port Channelized OC-12/DS0 SPAs and line cards
•1-Port Channelized OC-48/DS3 SPAs and line cards
•1-Port Channelized OC-3/STM-1 SPA
•2-Port Channelized OC-12c/DS0 SPA
Table 18 Overview: Configuring a Serial Interface on an E1 DS0 Channel
Step Task Module Section
1. Configure the T3 controller
parameters and set the SPA mode to
be E3.
21 E1 controllers are automatically
created.
“Configuring Clear Channel T3/E3
and Channelized T3 and T1/E1
Controllers on the
Cisco ASR 9000 Series Router”
Configuring a Channelized T3
Controller
2. Create and configure DS0 channel
groups on the E1 controllers.
“Configuring Clear Channel T3/E3
and Channelized T3 and T1/E1
Controllers on the
Cisco ASR 9000 Series Router”
Configuring an E1 Controller
3. Configure the Serial interfaces that
are associated channel groups you
created in Step 2.
Configuring Serial Interfaces on the
Cisco ASR 9000 Series Router
How to Configure Serial Interfaces
Table 19 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 on the
Cisco ASR 9000 Series Router”
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 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Configuring a Channelized T3
Controller
3. Create and configure DS0 channel
groups on the E1 controllers.
“Configuring Clear Channel
T3/E3 and Channelized T3 and
T1/E1 Controllers on the
Cisco ASR 9000 Series Router”
Configuring an E1 Controller
4. Configure the Serial interfaces that
are associated channel groups you
created in Step 2.
“Configuring Serial Interfaces on
the
Cisco ASR 9000 Series Router”
How to Configure Serial Interfaces

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Table 20 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
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 508.
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:
Table 20 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 on the
Cisco ASR 9000 Series Router”
Configuring a Clear Channel SONET
Controller for T3
2. Configure the STS stream mode for
T3 and configure the T3 controller
parameters.
“Configuring Channelized
SONET/SDH on the
Cisco ASR 9000 Series Router”
Configuring a Clear Channel SONET
Controller for T3
3. Configure the Serial interfaces. “Configuring Serial Interfaces on
the
Cisco ASR 9000 Series Router”
How to Configure Serial Interfaces

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•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 508.
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 on the Cisco ASR 9000 Series Router” 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 the following SPAs:
•1-Port Channelized OC-12/DS0 SPAs and line cards
•2-Port and 4-Port Channelized T3 SPAs
•8-Port Channelized T1/E1 SPA
•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.

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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 on the
Cisco ASR 9000 Series Router” 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).
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 During Minimal Disruptive Restart (MDR) keepalives may fail. Therefore the keepalive timers, on both
ends, should be either disabled or set to an interval longer than the MDR time.
Note Before performing a Minimal Disruptive Restart (MDR) upgrade, we recommend disabling keepalives
on a Cisco XR 12000 Series Router.
Note Before performing a Minimal Disruptive Restart (MDR) upgrade, we recommend configuring a
keepalive interval of 10 seconds or more on a Cisco CRS-1 Router.