Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Configuration Guide
Configuring Clear Channel SONET Controllers on the Cisco ASR 9000 Series Router
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Configuring Clear Channel SONET Controllers on the Cisco ASR 9000 Series Router

Table Of Contents

Configuring Clear Channel SONET Controllers on the Cisco ASR 9000 Series Router

Contents

Prerequisites for Configuring Clear Channel SONET Controllers

Information About Configuring SONET Controllers

SONET Controller Overview

Default Configuration Values for SONET Controllers

SONET APS

How to Configure Clear Channel SONET Controllers

Configuring a Clear Channel SONET Controller

Prerequisites

Configuring SONET APS

Prerequisites

Restrictions

Configuring a Hold-off Timer to Prevent Fast Reroute from Being Triggered

Prerequisites

Configuration Examples for SONET Controllers

SONET Controller Configuration: Example

SONET APS Group Configuration: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance


Configuring Clear Channel SONET Controllers on the Cisco ASR 9000 Series Router


This module describes the configuration of clear channel SONET controllers on the Cisco ASR 9000 Series Router.

SONET controller configuration is a prerequisite for configuring Inter-Chassis Stateful Switchover (ICSSO) for Point-to-Point Protocol (PPP) and Multilink PPP (MLPPP), channelized SONET, or serial interfaces on the Cisco ASR 9000 Series Router.

SONET allows you to define optical signals and a synchronous frame structure for multiplexed digital traffic. It is a set of standards defining the rates and formats for optical networks specified in American National Standards Institute (ANSI) T1.105, ANSI T1.106, and ANSI T1.117.

For more information about configuring a channelized SONET controller, see the Configuring Channelized SONET on the Cisco ASR 9000 Series Router module.

The commands for configuring the Layer 1 SONET controllers are provided in the
Cisco IOS XR Interface and Hardware Component Command Reference.

Feature History for Configuring SONET Controllers on Cisco IOS XR Software

Release
Modification
 

 

Release 3.9.0

Support for the following shared port adapter (SPA) was introduced on the Cisco ASR 9000 Series Router:

Cisco 2-Port Channelized OC-12/DS0 SPA


Contents

Prerequisites for Configuring Clear Channel SONET Controllers

Information About Configuring SONET Controllers

How to Configure Clear Channel SONET Controllers

Configuration Examples for SONET Controllers

Additional References

Prerequisites for Configuring Clear Channel SONET Controllers

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

Before configuring SONET controllers, be sure that the following tasks and conditions are met:

You have a 2-Port Channelized OC-12/DS0 SPA installed.

You know how to apply the specify the SONET controller name and instance identifier with the generalized notation rack/slot/module/port. The SONET controller name and instance identifier are required with the controller sonet command.

Information About Configuring SONET Controllers

To configure SONET controllers, you must understand the following concepts:

SONET Controller Overview

Default Configuration Values for SONET Controllers

SONET APS

SONET Controller Overview

In routers supporting Cisco IOS XR software, the physical ports on certain line cards are called controllers. Before you can configure channelized SONET or a serial interface, you need to configure the SONET controller.

The commands used to configure the physical SONET port are grouped under the SONET controller configuration mode. To get to the SONET controller configuration mode, enter the controller sonet command in global configuration mode. You can also preconfigure a SONET controller using the controller preconfigure sonet global configuration command.

The router uses SONET controllers for Layer 1 and Layer 2 processing.

Default Configuration Values for SONET Controllers

Table 4 describes some default configuration parameters that are present on SONET controllers.

Table 4 SONET Controller Default Configuration Values 

Parameter
Default Value
Configuration File Entry

Reporting of the following alarms for a SONET controller:

Bit 1 (B1) bit error rate (BER) threshold crossing alert (TCA) errors

Bit 2 (B2) BER TCA errors

Signal failure BER errors

Section loss of frame (SLOF) errors

Section loss of signal (SLOS) errors

enabled

To disable reporting of any alarms enabled by default, use the no report [b1-tca | b2-tca | sf-ber | slof | slos] command in SONET/SDH configuration mode.

To enable reporting of line alarm indication signal (LAIS), line remote defect indication (LRDI), or signal degradation BER errors, use the report [lais | lrdi | sd-ber] command in SONET/SDH configuration mode.

Reporting of the following alarms for a SONET path controller:

Bit 3 (B3) BER TCA errors

Path loss of pointer (PLOP) errors

enabled

To disable B3 BER TCA or PLOP reporting on the SONET path controller, enter the no report b3-tca or no report plop command in SONET/SDH path configuration submode.

To enable reporting of path alarm indication signal (PAIS), path payload mismatch (PPLM), path remote defect indication (PRDI), or path trace identity mismatch (PTIM) errors, use the report [ pais | pplm | prdi | ptim command in SONET/SDH path configuration submode.

Synchronous payload envelope (SPE) scrambling

enabled

To disable SPE scrambling on a SONET controller, enter the path scrambling disable command in SONET controller configuration submode.

Keepalive timer

enabled

To turn off the keepalive timer, enter the keepalive disable command in interface configuration mode.


SONET APS

The automatic protection switching (APS) feature allows switchover of interfaces in the event of failure, and is often required when connecting SONET equipment to telco equipment. APS refers to the mechanism of using a protect interface in the SONET network as the backup for working interface. When the working interface fails, the protect interface quickly assumes its traffic load. The working interfaces and their protect interfaces make up an APS group.

In Cisco IOS XR software, SONET APS configuration defines a working line and a protection line for each redundant line pair. The working line is the primary or preferred line, and communications take place over that line as long as the line remains operative. If a failure occurs on the working line, APS initiates a switchover to the protection line. For proper APS operation between two routers, a working line on one router must also be the working line on the other router, and the same applies to the protection line.

In a SONET APS group, each connection may be bidirectional or unidirectional, and revertive or non-revertive. The same signal payload is sent to the working and protect interfaces. The working and protect interfaces terminate in two different routers.

The protect interface directs the working interface to activate or deactivate in the case of degradation, loss of channel signal, or manual intervention. If communication between the working and protect interfaces is lost, the working router assumes full control of the working interface as if no protect circuit existed.

In an APS group, each line is called a channel. In bidirectional mode, the receive and transmit channels are switched as a pair. In unidirectional mode, the transmit and receive channels are switched independently. For example, in bidirectional mode, if the receive channel on the working interface has a loss of channel signal, both the receive and transmit channels are switched.

How to Configure Clear Channel SONET Controllers

This section contains the following procedures:

Configuring a Clear Channel SONET Controller

Configuring SONET APS

Configuring a Hold-off Timer to Prevent Fast Reroute from Being Triggered

Configuring a Clear Channel SONET Controller

This task explains how to configure SONET controllers as a prerequisite to configuring serial interfaces.

Prerequisites

You need to have a supported channelized SPA installed in a router that is running the corresponding supported Cisco IOS XR software release.

If you want to ensure recovery from fiber or equipment failures, then configure SONET APS on the router as describe in the "Configuring SONET APS" section.

SUMMARY STEPS

1. configure

2. controller sonet interface-path-id

3. clock source {internal | line}

4. line delay trigger value

5. line delay clear value

6. framing sonet

7. loopback {internal | line}

8. overhead {j0 | s1s0} byte-value

9. path keyword [values]

10. end
or
commit

11. show controllers sonet 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 

controller sonet interface-path-id

Example:

RP/0/RSP0/CPU0:router(config)# controller sonet 0/1/0/0

Enters SONET controller configuration submode and specifies the SONET controller name and instance identifier with the rack/slot/module/port notation.

Step 3 

clock source {internal | line}

Example:

RP/0/RSP0/CPU0:router(config-sonet)# clock source internal

Configures the SONET port transmit clock source, where the internal keyword sets the internal clock and line keyword sets the clock recovered from the line.

Use the line keyword whenever clocking is derived from the network. Use the internal keyword when two routers are connected back-to-back or over fiber for which no clocking is available.

Note The line clock is the default.

Step 4 

line delay trigger value

Example:

RP/0/RSP0/CPU0:router(config-sonet)# line delay trigger 3000

(Optional) Configures the SONET line delay trigger values, where the trigger values are in the range from 0 through 60000 milliseconds, and the default delay trigger value is 0 milliseconds.

Step 5 

line delay clear value

Example:

RP/0/RSP0/CPU0:router(config-sonet)# line delay clear 4000

(Optional) Configures the amount of time before a SONET line delay trigger alarm is cleared. The range is from 1000 through 180000 milliseconds, and the default is 10 seconds.

Step 6 

framing sonet

Example:

RP/0/RSP0/CPU0:router(config-sonet)# framing sonet

(Optional) Configures the controller framing with the sonet keyword for SONET framing.

SONET framing (sonet) is the default.

Step 7 

loopback {internal | line}

Example:

RP/0/RSP0/CPU0:router(config-sonet)# loopback internal

(Optional) Configures the SONET controller for loopback, where the internal keyword selects internal (terminal) loopback, or the line keyword selects line (facility) loopback.

Step 8 

overhead {j0 | s1s0} byte-value

Example:

RP/0/RSP0/CPU0:router(config-sonet)# overhead s1s0

(Optional) Configures the controller's overhead, where the j0 keyword specifies the STS identifier (J0/C1) byte, and the s1s0 keyword specifies bits s1 and s0 of H1 byte.

The default byte value for the j0 keyword is 0xcc, and the default byte value for the s1s0 keyword is 0.

The range of valid values for j0 and s1s0 is 0 through 255.

Step 9 

path keyword [values]

Example:

RP/0/RSP0/CPU0:router(config-sonet)# path delay trigger 25

(Optional) Configures SONET controller path values.

Keyword definitions are as follows:

ais-shut—Set sending path alarm indication signal (PAIS) when shut down.

b3-ber-prdi—Enable sending of a path-level remote defect indication (PRDI) when the bit error rate (BER) bit interleaved parity (BIP) threshold is exceeded.

delay clear value—Set the amount of time before a Synchronous Transport Signal (STS) path delay trigger alarm is cleared. Replace the value argument with a number in the range from 0 through 180000 milliseconds. The default value is 10 seconds.

delay trigger value —Set SONET path delay values or delay trigger value. Replace the value argument with a number in the range from 0 through 60000 milliseconds. The default value is 0 milliseconds.

overhead [c2 byte-value | j1 line] —Set SONET POH byte or bit values. Enter the c2 keyword to specify STS SPE content (C2) byte, and replace the byte-value argument with a number in the range from 0 through 255. Enter the j1 keyword to configure the SONET path trace (J1) buffer, and replace the line argument with the path trace buffer identifier (in ASCII text).

report [b3-tca | pais | plop | pplm | prdi | ptim]—Set SONET path alarm reporting. Specifies which alarms are reported and which bit error rate (BER) thresholds will signal an alarm. By default, B3 BER threshold crossing alert (TCA) and path loss of pointer (PLOP) reporting are enabled. Specifying the pais keyword sets PAIS reporting status; pplm sets path payload mismatch (PPLM) defect reporting status; prdi sets path remote defect indication reporting status; and ptim sets path trace identity mismatch (PTIM) defect reporting status.

The no report b3-tca and no report plop commands in SONET/SDH path configuration submode disable B3 BER TCA and PLOP reporting status, respectively.

scrambling disable—Disable SPE scrambling. Note that SPE scrambling is enabled by default.

threshold b3-tca BER—Set SONET path BER threshold value. Replace the BER argument with a number in the range from 3 through 9. The threshold value is interpreted as a negative exponent of 10 when determining the bit error rate. For example, a value of 5 implies a bit error rate of 10 to the minus 5. The default BER threshold value is 6.

uneq-shutSets sending Unequipped (UNEQ) when shut down.

Step 10 

end

or

commit

Example:

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

or

RP/0/RSP0/CPU0:router(config-sonet)# 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 11 

show controllers sonet interface-path-id

Example:

RP/0/RSP0/CPU0:router# show controllers sonet 0/1/0/0

Verifies the SONET controller configuration.

Configuring SONET APS

SONET APS offers recovery from fiber (external) or equipment (interface and internal) failures at the SONET line layer. This task explains how to configure basic automatic protection switching (APS) on the router and how to configure more than one protect or working interface on a router by using the aps group command.

To verify the configuration or to determine if a switchover has occurred, use the show aps command.

Prerequisites

You need to have a supported channelized SPA installed in a router that is running Cisco IOS XR software.

Restrictions

For proper APS operation between two routers, a working line on one router must also be the working line on the other router, and the same applies to the protection line.

The Cisco ASR 9000 Series Router supports multirouter APS only on the 2-Port Channelized OC-12/DS0 SPA.

SUMMARY STEPS

1. configure

2. aps group number

3. channel {0 | 1} local sonet interface

4. Repeat Step 3 for each channel in the APS group.

5. exit

6. interface loopback number

7. ipv4 address ip-address mask

8. exit

9. interface serial interface-path-id

10. ipv4 address ip-address mask

11. crc {16 | 32}

12. encapsulation {hdlc | ppp}

13. keepalive {interval | disable}[retry]

14. no shutdown

15. Repeat Step 9 to Step 13 for each channel in the group.

16. exit

17. controller sonet interface-path-id

18. ais-shut

19. path scrambling disable

20. clock source {internal | line}

21. Repeat Step 16 to Step 19 for each channel of the group.

22. end
or
commit

23. exit

24. exit

25. show aps

26. show aps group [number]

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

configure

Example:

RP/0/RSP0/CPU0:router# configure

Enters global configuration mode.

Step 2 

aps group number

Example:

RP/0/RSP0/CPU0:router(config)# aps group 1

Adds an APS group with a specified number and enters APS group configuration mode.

Use the aps group command in global configuration mode.

To remove a group, use the no form of this command, as in: no aps group number, where the value range is from 1-255.

Note To use the aps group command, you must be a member of a user group associated with the proper task IDs for aps commands.

Note The aps group command is used even when a single protect group is configured.

Step 3 

channel {0 | 1} local sonet interface

Example:

RP/0/RSP0/CPU0:router(config-aps)# channel 0 local SONET 0/0/0/1

Creates a channel for the APS group. 0 designates a protect channel, and 1 designates a working channel.

Note If the protect channel is local, it must be assigned using the channel command before any of the working channels is assigned.

Step 4 

Repeat Step 3 for each channel in the group.

Step 5 

exit

Exits APS group configuration mode and enters global configuration mode.

Step 6 

interface loopback number

Example:

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

(Optional) Configures a loopback interface if a two-router APS is desired and enters interface configuration mode for a loopback interface.

Note In this example, the loopback interface is used as the interconnect.

Step 7 

ipv4 address ip-address mask

Example:

RP/0/RSP0/CPU0:router(config-if)# ipv4 address 172.18.0.1 255.255.255.224

Assigns an IPV4 address and subnet mask to the loopback interface.

Step 8 

exit

Exits interface configuration mode for a loopback interface, and enters global configuration mode.

Step 9 

interface serial interface-path-id
Example:

or

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

Connects the interface for the channel selected in Step 3, and enters interface configuration mode.

For serial interfaces, specifies the complete interface number with the rack/slot/module/port/T3Num/T1num:instance notation.

Step 10 

ipv4 address ip-address mask

Example:

RP/0//CPU0:router(config-if)# ipv4 address 172.18.0.1 255.255.255.224

Assigns an IPv4 address and subnet mask to the interface.

Step 11 

crc {16 | 32}

Example:

or

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

Selects a CRC value for the channel. Enter the 16 keyword to specify 16-bit CRC mode, or enter the 32 keyword to specify 32-bit CRC mode. For serial interfaces, the default is 16.

Step 12 

encapsulation {hdlc | ppp} 
Example:

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

Set the Layer 2 encapsulation of an interface.

 

Step 13 

keepalive {interval | disable}[retry]

Example:

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

Sets the keepalive timer for the channel, where:

interval—Number of seconds (from 1 to 30) between keepalive messages. The default is 10.

disable—Turns off the keepalive timer.

retry—(Optional) Number of keepalive messages (from 1 to 10) that can be sent to a peer without a response before transitioning the link to the down state. The default is 3.

 

Step 14 

no shutdown

Example:

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

Removes the shutdown configuration.

The removal of the shutdown configuration removes the forced administrative down on the interface, enabling that interface to move to an up or down state (assuming the parent SONET layer is not configured administratively down).

Step 15 

Repeat Step 9 through Step 13 for each channel in the group.

Step 16 

exit

Exits interface configuration mode, and enters global configuration mode.

Step 17 

controller sonet interface-path-id

Example:

RP/0/RSP0/CPU0:router(config)# controller sonet 0/1/0/0

Enters SONET controller configuration mode and specifies the SONET controller name and instance identifier with the rack/slot/module/port notation.

Step 18 

ais-shut

Example:

RP/0/RSP0/CPU0:router(config-sonet)# ais-shut

Configures SONET path values such as alarm indication signal (AIS) at shut down.

Step 19 

path scrambling disable

Example:

RP/0/RSP0/CPU0:router(config-sonet)# path scrambling disable

(Optional) Disables synchronous payload envelope (SPE) scrambling.

Note SPE scrambling is enabled by default.

Step 20 

clock source {internal | line}

Example:

RP/0/RSP0/CPU0:router(config-sonet)# clock source internal

Configures the SONET port TX clock source, where the internal keyword sets the internal clock and the line keyword sets the clock recovered from the line.

Use the line keyword whenever clocking is derived from the network; use the internal keyword when two routers are connected back-to-back or over fiber for which no clocking is available.

The line clock (line) is the default.

Step 21 

Repeat Step 16 through Step 19 for each channel in the group.

Step 22 

end

or

commit

Example:

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

or

RP/0/RSP0/CPU0:router(config-sonet)# 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 23 

exit

Exits SONET controller configuration mode, and enters global configuration mode.

Step 24 

exit

Exits global configuration mode, and enters EXEC mode.

Step 25 

show aps

Example:

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

(Optional) Displays the operational status for all configured SONET APS groups.

Step 26 

show aps group [number]

Example:

RP/0/RSP0/CPU0:router# show aps group 3

(Optional) Displays the operational status for configured SONET APS groups.

Note The show aps group command is more useful than the show aps command when multiple groups are defined.

Configuring a Hold-off Timer to Prevent Fast Reroute from Being Triggered

When APS is configured on a router, it does not offer protection for tunnels; because of this limitation, fast reroute (FRR) still remains the protection mechanism for Multiprotocol Label Switching (MPLS) traffic-engineering.

When APS is configured in a SONET core network, an alarm might be generated toward a router downstream. If the router downstream is configured with FRR, you may want to configure a hold-off timer at the SONET level to prevent FRR from being triggered while the CORE network is doing a restoration. Perform this task to configure the delay.

Prerequisites

Configure SONET APS, as describe in the "Configuring SONET APS" section.

SUMMARY STEPS

1. configure

2. controller sonet interface-path-id

3. line delay trigger value
or
path delay trigger value

4. 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 

controller sonet interface-path-id

Example:

RP/0/RSP0/CPU0:router(config)# controller sonet 0/6/0/0

Enters SONET configuration mode.

Step 3 

line delay trigger value

or

path delay trigger value

Example:

RP/0/RSP0/CPU0:router(config-sonet)# line delay trigger 250

or

RP/0/RSP0/CPU0:router(config-sonet)# path delay trigger 300

Configures SONET port delay trigger values in milliseconds.

Tip The commands in Step 2 and Step 3 can be combined in one command string and entered from global configuration mode like this: controller sonet r/s/m/p line delay trigger or controller sonet r/s/m/p path delay trigger.

Step 4 

end

or

commit

Example:

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

or

RP/0/RSP0/CPU0:router(config-sonet)# 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 SONET Controllers

This section contains the following examples:

SONET Controller Configuration: Example

SONET APS Group Configuration: Example

SONET Controller Configuration: Example

The following example shows the commands and output generated when you are performing the configuration of a SONET controllers following the steps outlined in the "Configuring a Clear Channel SONET Controller" section. This example shows the usage of every optional command, along with listings of options within commands where relevant. An actual configuration may or may not include all these commands.

configure
controller sonet 0/1/0/0
	ais-shut 
	clock source internal
	framing sonet
	loopback internal
Loopback is a traffic-effecting operation
	overhead s1s0 1
	path ais-shut
	path delay trigger 0
	path overhead j1 line l1
	path report pais
	path scrambling disable   
	path threshold b3-tca 6
	path uneq-shut 
	report pais
	threshold b2-tca 4
	commit

SONET APS Group Configuration: Example

The following example shows SONET Remote (two routers) APS configuration.

RP/0/0/CPU0:router(config)# aps group 1
	channel 0 local SONET 0/0/0/1
	channel 1 remote 172.18.69.123
	signalling sonet
	commit
show aps
show aps group 3

Additional References

The following sections provide references related to SONET controller configuration.

Related Documents

Related Topic
Document Title

Cisco IOS XR master command reference

Cisco IOS XR Master Commands List

Cisco IOS XR interface configuration commands

Cisco IOS XR Interface and Hardware Component Command Reference

Initial system bootup and configuration information for a router using the Cisco IOS XR Software

Cisco IOS XR Getting Started Guide

Information about user groups and task IDs

Configuring AAA Services on Cisco IOS XR Software module of Cisco IOS XR System Security Configuration Guide

Information about configuring router interfaces and other components from a remote Craft Works Interface (CWI) client management application

Cisco Craft Works Interface Configuration Guide


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.


MIBs

MIBs
MIBs Link

There are no applicable MIBs for this module.

To locate and download MIBs for selected platforms using
Cisco IOS XR Software, use the Cisco MIB Locator found at the following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml


RFCs

RFCs
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.


Technical Assistance

Description
Link

The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/techsupport