Release Notes for Cisco IOS Release 12.2(12)DA for Cisco DSLAMs with NI-2

These release notes describe features and caveats in Cisco IOSRelease 12.2(12)DA for the Cisco 6015, Cisco 6160, and Cisco 6260 digital subscriber line access multiplexers (DSLAMs).

Note When you upgrade from Cisco IOS Release 12.1(5)DA1 or earlier images on the NI-2 card to Release 12.2(12)DA, you must format the bootflash on the NI-2 card before loading the Release 12.2(12)DA dboot image. See the "Limitations and Restrictions" section.

System Requirements

New and Changed Information

This section provides new and changed information for Cisco IOS Release 12.2(12)DA and 12.2(10)DA.

Enhanced Cisco OC-3c/OC-3c NI-2 Card Overview

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The Cisco OC-3c/OC-3c NI-2 card has been enhanced to support quality of service (QoS) in a fully loaded chassis of G.SHDSL SHTU-C (8xG.SHDSL) line cards. This enhancement eliminates the random cell drops that previously occurred in a chassis loaded with more than 16 G.SHDSL line cards.

Use the enhanced NI-2 card if you plan to deploy more than 16 G.SHDSL line cards in a Cisco DSLAM.

Notes A Cisco DSLAM can support either legacy or enhanced NI-2 cards.

The new NI-2 cards (NI-2-155SM-155SM2 and NI-2-155MM-155MM2) support Cisco IOS Release 12.1(7)DA2 or later; however, the card's new features are only enabled in Release 12.2(12)DA or later.

Feature Description

This section describes how the Cisco OC-3c/OC-3c NI-2 card was enhanced to support QoS in a fully loaded chassis of G.SHDSL SHTU-C (8xG.SHDSL) line cards.

To accommodate these enhancements, the following changes were made to the legacy NI-2 card:

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The upstream field programmable gate array (FPGA) was enhanced to support QoS tables for the upstream traffic manager (UPTM).

The DSLAM automatically builds the upstream QoS tables using the QoS values defined by commands such as atm connection-traffic-table-row and atm pvc. (See the "New and Changed Software for New Cisco OC-3c/OC-3c NI-2 Cards" section for a list of atm commands used to set upstream QoS table values.)

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The size of the bootflash memory and main dynamic RAM (DRAM) were increased (see Table 1).

Cisco 6100 DSLAM
Cisco 6130 DSLAM
Cisco 6015 DSLAM
Cisco 6160 DSLAM
Cisco 6260 DSLAM

Table 1 shows the memory enhancements made to the new Cisco OC-3c/OC-3c NI-2 card.

New and Changed Software for New Cisco OC-3c/OC-3c NI-2 Cards

The following list describes the software changes made to accommodate the enhanced NI-2 card:

Table 1 NI-2 Memory Enhancements
Memory Type	New NI-2 Card	Legacy NI-2 Card
Main DRAM	128 MB	64 MB
Flash	16 MB	16 MB
Bootflash	8 MB	4 MB

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The following atm commands were enhanced to accommodate upstream QoS tables. In addition to configuring the QoS values for the ATM switch component of the DSLAM, these commands now also define the values for the upstream QoS tables.

atm clp-drop
atm connection-traffic-table-row
atm input-queue
atm input-threshold
atm pvc
atm soft-vc

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The show ni2-switch registers and show ni2-switch memory commands have been enhanced to show upstream field programmable gate array (FPGA) data. For more information, see the description of these commands in the Command Reference for Cisco DSLAMs with NI-2.

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Two new object identifiers (OIDs) were added to the CISCO-ENTITY-VENDORTYPE-OID-MIB for the enhanced Cisco OC-3c/OC-3c NI-2 cards:

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The policer function was modified to reduce congestion in the DSLAM. The policer was moved to the upstream FPGA, which is closer to the upstream source. Note that as a result of this change, the DSLAM experiences low data throughput when policing on peak cell rate (PCR) with a large packet size and a data rate that greatly exceeds the selected PCR.

Cisco OC-3c/OC-3c NI-2 Card Requirements

The following requirements apply to legacy and enhanced Cisco OC-3c/OC-3c NI-2 cards:

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Cisco IOS Release 12.2(12)DA or later. The enhanced NI-2 card supports Release 12.1(7)DA2 or later. However, the card's new features are only enabled in Release 12.2(12)DA or later.

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A new ni2-dboot2-mz image (which is shipped preinstalled in the NI-2 bootflash memory).

Note

The old dboot image does not work on enhanced NI-2 cards. If you load a dboot image onto a new NI-2 card, the NI-2 card becomes inoperable. (See the "Correcting Bootup Problems" section for instructions on how to recover if this happens.)

New Software Features in Release 12.2(12)DA

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The Octal-Port DMT ATU-C over ISDN (8xDMT over ISDN) line card has been enhanced to operate with the following customer premises equipment (CPEs):

Note

Alcatel-based CPEs and Cisco SOHO 76 and 826 CPEs require Cisco IOS Release 12.2(4)YA2 or later. We also recommend that you issue the dsl operating-mode annexb-ur2 command at the CPE to enable DMT operating mode on these CPEs.

New Hardware Features in Release 12.2(10)DA

New Software Features in Release 12.2(10)DA

The following new software features were introduced in Cisco IOS Release 12.2(10)DA.

DMT Power-Management-Additional-Margin

The 8xDMT line card can run in power-management mode in the G.dmt or the T1.413 mode. The resulting power cutback produces a reduction in power dissipation and crosstalk. Only 8xDMT line cards support power management. All CPEs may not support the DSL functionality for power management to function correctly. Check with a Cisco customer representative to verify CPE compatibility with the 8xDMT power management.

You control the power management feature by including a dmt power-management-additional-margin command in a profile and assigning that profile to a line card interface. This Cisco IOS software command allows you to set the additional margin for each channel from 0 dB (off) to 15 dB. This sets the additional margin that will be added to the target margin. If the sum of the target margin and additional margin exceeds 15dB, it is capped at 15dB. If the actual margin of the line is higher than the sum of the configured target and additional margin, and all the above conditions are met, then power management attempts to reduce the actual margin, and as a consequence the power level as well.

Not all CPE support power management. If you connect an unsupported CPE to a port on which power management is turned on, you will not see a reduction in the actual margin or power level. The operating modes supported by power management are T1.413and G-992-1 (G.DMT). Table 2 shows the CPE and specifies which operating mode supports them.

Table 2 CPEs and Power Management Support
CPE	G.DMT	T1.413
Cisco 677 CPE	not supported	not supported
Cisco 678 CPE	not supported	supported
Cisco SOHO 77/Cisco 827 CPEs	supported	supported
ADSL WAN Interface Card (WIC)	supported	supported
Alcatel chipset based modem	supported	supported

A reduction in the power level occurs if there is excess margin on the line. For the downstream direction, if there is excess margin, then IOS displays a reduction in margin for the modes listed above, and a reduction in transmit power for T1.413 mode. For the upstream direction, if there is excess margin, then Cisco IOS software displays a reduction in the margin for G-992-1 mode only. Cisco IOS software does not display a reduction in transmit power for the upstream direction.

ATM OAM Cells Supported in Fast Path Mode

The NI-2 card now supports ATM OAM cells through fast path mode. Also, you can now use the ping atm utility command in fast path mode.

Enhanced ATM OAM Segment Cells Support

A new command, atm oam intercept segment, allows you to enable or disable receiving ATM OAM segment cells on valid connections. By default, ATM OAM cells received on unconfigured or down connections are dropped. For more information, see the Command Reference for Cisco DSLAMs with NI-2.

MIB Object Changes

This release contains changes to the following Management Information Base (MIB) objects:

The power management feature is configurable through the CISCO-ADSL-DMT-LINE-MIB. The MIB object cAdslAtucDmtConfPMAddSnrMgn configures the downstream component and the MIB object cAdslAturDmtConfPMAddSnrMgn configures the upstream component on that particular DSL profile. Both objects have a default value of 0 and can be configured from 0 to 150 tenths of a dB in increments of 10. Using SNMP to set the objects to 0 disables the power management feature on the ports.

Installation Notes

The following sections provide useful information for Cisco IOS Release 12.2(12)DA installation and operation:

Upgrade Bootflash on a Legacy NI-2 Card to the 12.2(12)DA dboot Image

When you upgrade from Cisco IOS Release 12.1(5)DA1 or earlier images on a legacy NI-2 card to Release 12.2(12)DA, you must reformat the bootflash on the NI-2 card.

If you are upgrading from Cisco IOS Release 12.1(7)DA3, 12.2(1b)DA1, 12.2(5)DA1, or 12.2(7)DA you do not need to reformat the bootflash. You can skip this section and follow the DSLAM upgrade procedure at the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/dsl_prod/ios_dsl/rel122/config/04conf09.htm

Note We recommend that you have console access to the NI-2 card during the upgrade procedure. You can use the console connection to troubleshoot any unexpected events that occur during the upgrade.

To upgrade the boot image on a legacy NI-2 card, perform the following steps in privileged EXEC mode:


	Command	Purpose
Step 1	DSLAM# show hardware	Verify the type of Cisco OC-3c/OC-3c NI-2 card installed in the chassis to determine whether to download a new dboot image: •NI2-155MM-155MM2 or NI2-155SM-SM2—Indicates a new Cisco OC-3c/OC-3c NI-2 card, which is shipped with the correct image (dboot2) preinstalled. Skip this procedure and the following procedure. •Any other value—Indicates a legacy NI-2 card, which may need to be updated with a new image. Continue with this procedure.
Step 2	DSLAM# dir bootflash:	Verify that the bootflash image is ni2-dboot-mz.121-5.da1 or ni2-dboot-mz.121-4.da. If it is neither, go to the "Upgrade Bootflash on a Legacy NI-2 Card to the 12.1(5)DA1 dboot Image" section and perform the instructions there, and then return to this step. This is required because of a problem (CSCdr89374) in old bootflash images.
Step 3	DSLAM# dir flash:	Determine the name of the flash file that begins with ni2- and use it as filename in Step 4.
Step 4	DSLAM# delete flash:filename	Delete the flash file name found in Step 3. Repeat Step 3 and Step 4 until all files in the flash file have been deleted.
Step 5	DSLAM# squeeze flash:	Recover available space in flash memory.
Step 6	DSLAM# copy tftp://tftpserver:TFTPBOOT/ni2 -dsl-mz.122-12.da flash:	Copy the Cisco IOS software image from a TFTP server to flash.
Step 7	DSLAM# configure terminal DSLAM (config)# no boot system DSLAM (config)# boot system flash:ni2-dsl-mz.122-12.da DSLAM# end	Enter global configuration mode. Disable the boot from system. Specify the name of the system image to load at startup. Exit global configuration mode.
Step 8	DSLAM# copy running-config startup-config	Save your changes to the startup configuration.
Step 9	DSLAM# reload	Reload the system to upgrade the image.
Step 10	DSLAM# show version	Confirm that the running image is ni2-dsl-mz.122-12.da. If it is not, go to Step 6.
Step 11	DSLAM# format bootflash:	Erase all information in bootflash memory. Answer y to all confirm questions. When the DSLAM returns to the EXEC prompt, bootflash memory is successfully formatted and ready for use. Ensure that the bootflash is 3.8 MB total. If it is not, go to Step 5.
Step 12	DSLAM# copy tftp://tftpserver:TFTPBOOT/ni2 -dboot-mz.122-12.da bootflash:	Copy the boot image from a TFTP server to the bootflash.
Step 13	DSLAM# reload	Reload the system to upgrade the image.

Upgrade Bootflash on a Legacy NI-2 Card to the 12.1(5)DA1 dboot Image

When you upgrade from Release 12.1(3)DA or earlier images on a legacy NI-2 card to Release 12.1(5)DA1, we recommend that you upgrade the bootflash image on the NI-2 card to the 12.1(5)DA1 dboot image.

To upgrade the dboot image in bootflash on a legacy NI-2 card, perform the following steps:


	Command	Purpose
Step 1	DSLAM> enable Password: <password> DSLAM#	Enter enable mode. Enter the password. The enable mode prompt is DSLAM#.
Step 2	DSLAM# delete bootflash:filename	Make room in the bootflash by deleting the name of the current boot image.
Step 3	DSLAM# squeeze bootflash	Recover available space in bootflash using the squeeze bootflash command.
Step 4	DSLAM# copy tftp://[server name] /[directory]/ni2-dboot-mz.121-5.da1 bootflash:	Copy the boot image to the bootflash.
Step 5	DSLAM# show version	Record the current value of the config-register that appears on the last line of the show version display.
Step 6	DSLAM# configure terminal	Enter global configuration mode, which has a prompt of `DSLAM(config)#`.
Step 7	DSLAM(config)# config-register 0	Set the config register to 0x0000 so that the NI-2 card reboots in the ROM monitor.
Step 8	DSLAM(config)# exit	Exit global configuration mode.
Step 9	DSLAM# copy running-config startup-config	Save the running configuration.
Step 10	DSLAM# reload	Reset the system.
Step 11	rommon> set	If you see BOOTLDR after you enter this command, the image in bootflash is already being used as the bootstrap image; go to Step 15. Otherwise, go to Step 12 and enter the commands in Steps 12 through 14 to force the system to use ni2-dboot-mz.121-5.bin as the bootstrap image.
Step 12	rommon> unset BOOTLDR	Unset BOOTLDR to remove the variable.
Step 13	rommon> sync	Sync to save the state of rommon.
Step 14	rommon> b	When the NI-2 card boots, it uses ni2-dboot-mz.121-5da.bin as the bootstrap image.
Step 15	DSLAM# configure terminal	Enter global configuration mode, which has a prompt of `DSLAM(config)#`.
Step 16	DSLAM(config)# config-register value	Set the config-register to the value you recorded in Step 5.
Step 17	DSLAM(config)# exit	Return to enable mode. Go to the "Limitations and Restrictions" section.

Booting the Enhanced OC-3/OC-3 NI-2 Card

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The new NI-2 cards (NI-2-155SM-155SM2 and NI-2-155MM-155MM2) work only with a new ni2-dboot2-mz image that is shipped preinstalled in the NI-2 bootflash. New NI-2 cards do not run with an old dboot image.

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Legacy NI-2 cards require an ni2-dboot-mz image; they do not run with the new dboot2 image.

To boot the enhanced Cisco OC-3/OC-3 NI-2 card, follow the instructions in the Configuration Guide for Cisco DSLAMs with NI-2. See the section "Booting from Flash Memory Configuration Tasks" in chapter 9, "Loading System Software Images and Configuration Files," at the following URL:

Correcting Bootup Problems

If you attempt to run an incorrect dboot or dboot2 image, or you attempt to boot a new NI-2 card with legacy Cisco IOS software before booting the new dboot2 image, the DSLAM becomes inoperable. If this occurs, see the following sections for information about how to correct the problem and make the DSLAM operational:

Running Cisco IOS Release 12.1(7)DA2 to 12.2(10)DA on a New NI-2 Card

You can run Cisco IOS Releases 12.1(7)DA2 to 12.2(10)DA on the new NI-2 cards (NI2-155MM-155MM2 and NI2-155SM-155SM2). However, before you attempt to boot the Cisco IOS software from flash, you must first boot the ni2-dboot2-mz (dboot2) image from bootflash.

Note To run Cisco IOS releases earlier than Release 12.2(12)DA on a new NI-2 card, do not boot from flash until you have booted the ni2-dboot2-mz image from bootflash. Otherwise, the DSLAM becomes inoperable.

If you encounter problems booting Cisco IOS Release 12.1(7)DA2 to 12.2(10)DA on the new NI-2 cards, perform the following steps to correct the problem and make the DSLAM operational:

Step 1

Issue the following command in to ensure that the correct dboot2 image is loaded in bootflash memory:

Step 2

Check the command output to make sure the FPGA major revision is 3 (see highlighted text below). This indicates that the dboot2 image is loaded.

Step 3

Issue the following command in global-configuration mode to set the configuration register to load the DSLAM image from the boot system commands in the startup configuration file:

Step 4

Exit configuration mode and reload (reboot) the DSLAM to make the DSLAM operational. This process loads the images in the correct order: dboot2 and then the legacy Cisco IOS software.

Using Rommon to Recover from Corrupted dboot2 Images

This procedure describes how to use ROM monitor (rommon) mode to recover from problems caused by an invalid or corrupt dboot2 image. This procedure uses the xmodem command to retrieve a valid dboot2 image from a PC or network server.

Note The xmodem command used in this procedure is extremely slow. Therefore, only perform this procedure if all other attempts to obtain a dboot2 image fail. Also note that the command is supported only on the new NI-2 cards (NI2-155MM-155MM2 and NI2-155SM-155SM2).

Step 1

Log in to the DSLAM through a console port. The rommon prompt (rommon>) should be displayed. If it is not, get into configuration mode and issue the command config-register 0x0 end write reload.

Step 3

Issue the following command to manually boot the DSLAM from bootflash.

Step 4

If Step 3 worked, you need not perform the rest of this recovery procedure. Instead, you should boot the Cisco IOS software and proceed to Step 7.

If Step 3 did not work, the rommon prompt is returned and you must proceed to Step 5 to continue with the recovery procedure.

Step 5

If the correct dboot2 image is not in bootflash or the image is corrupt, perform the following steps to use the xmodem command to download a valid dboot2 image to use to boot the DSLAM:

Open a terminal emulation window (such as Hyper Terminal) on a PC that is connected to the DSLAM through a console port.

Configure the following terminal emulation settings: port = com1 or com2, data rate = 9600, bits = 8, parity = none, stop bits = 1. You must use these values for the recovery procedure to work.

Make sure that the PC contains a valid dboot2 image or is connected to a network where a dboot2 image is stored on a server.

On the DSLAM, issue the following command to copy the dboot2 image to the specified filename. The command creates a temporary copy of the dboot2 image on the DSLAM; therefore, you must copy the image to bootflash or it will be lost when you reload the DSLAM (Step 6).

In the Hyper Terminal window on the PC, click Transfer in the menu bar at the top of the window and select Send File.

Select Xmodem as the protocol, and specify the name of the dboot2 image to copy to the DSLAM.

Step 6

To complete the recovery procedure, copy the dboot2 image to bootflash memory (for example, using TFTP). If you do not perform this step, the dboot2 image will be lost when you reload the DSLAM.

Limitations and Restrictions

The following sections describe the limitations and restrictions for Cisco IOS software DSLAM releases.

Redundant NI-2 Card Operation

When using NI-2 cards in a redundant fashion, we recommend that you issue the command redundancy reload-peer on the active NI-2 card after the system has loaded. This causes the redundant NI-2 to reload and ensures that the redundant configuration is operational.

In rare instances during testing, a redundant NI-2 card sometimes appeared to be functional but was not. Issuing the redundancy reload-peer command corrected the problem every time.

Attainable Bit Rate Is Conservative on 4xflexi-DMT and 8xDMT

Limitations

Due to line condition variations between trains, the effect of trellis encoding, interleave delay, FEC check bytes, and so forth, the attainable bit rate estimate is not always 100 percent accurate. A conservative approach was taken in making the estimate; therefore, in general, you can get a higher rate than what the estimate suggests. For a fast-path scenario, the results should track fairly closely for the downstream rate and err on the conservative side for the upstream rate. For an interleave path scenario, the results are highly dependent on configurations.

At a higher reach or where line conditions are not optimal, trellis encoding, interleave delay, and FEC check bytes can provide a much higher rate than was estimated (greater than 128 kbps).

Workaround

There is no workaround. The aggregate bit rate calculation is an estimate, which does not accurately model all of the line conditions that affect the true attainable bit rate for a given profile. The calculations for aggregate bit rate are performed as follows:

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The downstream capacity is obtained from the number of Reed-Solomon payload bytes per frame exchanged during line training, that is, the K value. The per-second estimate is then calculated from this K value. An extrapolated margin value is derived from the per-second estimate to make sure that if the line is trained at the estimated rate, it has an adequate margin.

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For upstream, unlike downstream, the Reed-Solomon payload bytes per frame is not readily available. Furthermore, unlike downstream, which requires a CPE EOC response to know the downstream margin, the upstream margin is readily available at the CO (upstream margin is measured at the CO end). Using this upstream margin and the number of bins utilized for upstream, an estimate of upstream attainable bit rate is made. (The associated DDTS numbers are CSCdv05351 and CSCdv05322.)

CPE Performance Issues with Overhead Framing Modes 0, 1 and 2

The CPE does not train or perform reliably when the Discrete Multitone (DMT) profile is set to use overhead framing mode 0, 1, or 2.

Workaround

Overhead framing mode 3 is designed for use with ATM. While overhead framing mode 1, which is not currently supported, is designed for Synchronous Transport Module (STM) mode. Configure your profiles to use overhead framing mode 3. Overhead framing mode 3 uses only 32 bytes of administrative overhead. Compared with overhead framing mode 1, it allows more bandwidth to be allocated to user data.

Trellis Encoding Enable Default Recommendations

Trellis encoding is disabled by default on the NI-2 card because it is not supported on the 4xDMT (ATUC-1-4DMT) line card. However, trellis encoding is supported on the 4xFlexiDMT (ATUC-4FLEXIDMT) line card and the 8xDMT (ATUC-1-DMT8 and ATUC-1-DMT8-I) line cards.

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For 4xDMT (ATUC-1-4DMT) ports—Disable trellis encoding in the DSL profile for those ports.

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For 4xFlexiDMT (ATUC-4FLEXIDMT) ports—Enable trellis encoding, except with ADI chipset-based CPEs that use ADI firmware prior to ADI 3.1. This includes all Cisco 677 and Cisco 627 CPEs.

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For 8xDMT (ATUC-1-DMT8 and ATUC-1-DMT8-I) ports—The default DMT setting for trellis encoding is auto-sense, which means that the 8xDMT line card attempts to automatically configure itself for the type of encoding supported on the CPE. If the auto-sense feature does not work, you may have to enable trellis encoding in the DSL profile for these ports.

Note

If you are unsure if your CPE supports trellis encoding, check with the manufacturer.

For information about how to change trellis encoding settings on the NI-2 card, see the documentation at the following location:

http://www.cisco.com/univercd/cc/td/doc/product/dsl_prod/ios_dsl/rel122/config/04conf04.htm#xtocid1734531

Restrictions on IP Services

Restricted Layer 3 Services

Cisco IOS Release 12.2(10)DA does not support the following Layer 3 services (or else these services are limited, as noted):

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The maximum number of MPLS/VPN for PPPoA terminations is 25 VPNs for PPPoA and 1 VPN for PPPoE.

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We recommend that you use a virtual template for PPPoX termination rather than a dialer interface.

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Up to 32 subinterfaces can be used for IP termination under the trunk or subtend ports.

Integrated Routing and Bridging Not Supported

MPLS VPN mapping of RFC 1483 routed sessions must not be confused with Integrated Routing and Bridging (IRB). IRB is not supported by MPLS VPN mapping of RFC 1483 routed sessions.

VPN Interfaces Restricted to Trunk Interfaces

Do not configure subtended interfaces for MPLS VPN services. Only trunk interfaces support MPLS VPN mapping of RFC 1483 routed sessions.

MPLS ATM-Label Switch Router Functionality Not Supported

DSLAMs are not meant for use as MPLS ATM-Label Switch Routers (ATM-LSRs). When designing your network, keep in mind that DSLAMs act only as Label Edge Routers (LERs).

Performance Restrictions for MPLS VPN Traffic

MPLS VPN-enabled interfaces do not perform as well as switched VCs. Please take this into consideration when deploying MPLS VPNs in your networks.

Restricted MPLS Features

The following MPLS-related features are not part of the MPLS VPN mapping of RFC 1483 routed sessions:

DSL Interface Limitations

In DSLAMs, each DSL interface can support multiple permanent virtual circuits (PVCs), but we recommend that you use one routed MPLS VC if a dynamic routing protocol (such as RIP) is used between the customer equipment and the provider equipment.

MPLS VPN Mapping Not Supported on the Eight-Port IDSL ITU-C Line Card

Routed termination of IDSL connections has not been supported since Cisco IOS Release 12.2(1b)DA.

Frame Relay PVCs/Soft PVCs on an IDSL Interface

The number of Frame Relay PVCs/Soft PVCs on an IDSL interface is restricted to 1 if you use the default row in a frame-relay connection traffic table (FR-CTT).

When upgrading to Release 12.2(10)DA from earlier releases, you must first create a new row in the FR-CTT with the desired CIR value and use the resultant row number during PVC/Soft PVC creation. If you do not create a new row, the second FR PVC/Soft PVC command is not parsed and installed on the IDSL interface.

Use of a Ring Topology in a DSLAM Subtend Environment to Achieve ATM Trunk Redundancy

Ring topology is achieved when a node in the subtend tree is attached to the ATM access to provide a physically redundant loop. Thus, when the primary ATM access or one of the ATM trunks in the subtend tree fails, the soft permanent virtual circuits (SPVCs) can be dynamically rerouted through the use of Private Network-Network Interface (PNNI) ( Figure 1).

This redundancy requires the use of SPVCs. If you use permanent virtual circuits (PVCs) or permanent virtual paths (PVPs), redundancy cannot be provided. The use of the SPVCs allows traffic to be rerouted around the failed access point, because SPVCs leverage this feature of PNNI. When the failure occurs, the SPVCs are disconnected and dynamically reconnected across the new path ( Figure 2).

Requirements

If you implement ring topology in a DSLAM subtend to achieve ATM trunk redundancy, the following requirements apply:

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You must use SPVCs, PNNI, ATM signaling, and Interim Local Management Interface (ILMI) to enable rerouting. PNNI, ATM signaling, and ILMI are enabled by default. Permanent connections such as PVCs and shaped virtual paths (VPs) do not benefit from the redundant link.

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You must make the redundant link's PNNI administrative weight higher than the PNNI weight of the primary trunk. Once you change the weight of the redundant link, the subtend tree uses this link only if a failure occurs.

Limitations

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Increase in latency as well as an increase in cell delay variation (CDV) between the cells. Delay-sensitive traffic, such as voice and video, or traffic that is susceptible to jitter, such as constant bit rate (CBR) voice, might be compromised. This technique is best realized for unspecified bit rate (UBR) traffic, such as consumer internet access, where no strict quality of service (QoS) objectives are required.

Once the redundant link is active, the following occurrences are potential problems:

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Greater possibility of increased congestion in the DSLAM ATM switch fabric, which might cause loss of data.

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When the main link is restored, there is downtime while the path is being rerouted. After the SPVCs are rerouted to the redundant ATM trunk and the original trunk is repaired or brought back into service, you must manually intervene. You must flap (shut/noshut) the subtend port. Because of retries on the current path, you must keep the trunk down until the maximum retry interval expires.

Cisco DSL Manager

If you are using versions of Cisco DSL Manager (CDM) earlier than CDM Release 3.4—from CDM Release 1.0 to CDM Release 3.3(3)—do not upgrade the DSLAMs to this new Cisco IOS release.

If you use both the CDM network management application and the Cisco IOS command line interface to manage your Cisco DSLAMs, you should be aware of certain configuration and procedural implications. Refer to the Release Notes for the Cisco DSL Manager, Release 3.4, for this information.

Important Notes

This section provides important information about Cisco IOS software releases for DSLAMs.

Line Card Features

Table 3 shows which line card features are available on the 4xDMT, 4xFlexi, and 8xDMT line cards.

Table 3 Line Card Features
Feature	4xDMT	4xFlexi	8xDMT
Interleave	yes	yes	yes
Fastpath	no	yes	yes
Min rate blocking	alarm only	yes	yes
SNR margin	alarm only	alarm and retrain capable	alarm and retrain capable
Trellis encoding	no	yes Disable on ADI based CPEs.	yes Ignores profile setting. The line card firmware automatically controls trellis encoding based on the CPE type.
Overhead framing	Mode 0,1,2,3 with ADI based CPE Mode 3 is recommended with other CPE.	Mode 3 only	Mode 3 only
Power Management Additional Margin	no	no	T1.413 G.DMT
Operating mode	T1.413 G.DMT G.Lite Auto	T1.413 G.DMT G.Lite Auto	T1.413 G.DMT G.Lite Auto
Training mode	Quick recommended	No affect	No affect
Cisco 677 CPE support	yes	yes	yes
Cisco 678 CPE support	no	yes	yes
Alcatel-based CPEs	limited performance	yes	yes

NI-2 Card IP Services

During system startup, the following protocol warning messages display. You can ignore these messages.

Soft PVC Address Changes upon Upgrade from Release 12.1(4)DA or Earlier

When you upgrade from Cisco IOS Release 12.1(4)DA or earlier to Release 12.2(10)DA, the default soft PVC addresses on all interfaces change. This occurs only when you upgrade to Release 12.2(10)DA from Release 12.1(4)DA or earlier.

Configuring Cisco Routers for Use with IDSL

If you wish to use a Cisco router for an IDSL application and the router is running a Cisco IOS release earlier than Release 12.1, you must configure the ISDN switch type. If you do not configure the ISDN switch type on the Cisco router, the router's BRI interface might not come back up after the IDSL line goes down and comes back up.

To prevent this problem from occurring, execute the isdn switch-type basic-ni command in global configuration mode on the router.

This problem does not occur if the Cisco router is running Cisco IOS Release 12.1 or later.

Assigning VPI Values to Shaped VP Tunnels

This release supports the full range of VPI values: 0 to 255. However, if you configure VP tunnels with traffic shaping, you can use only 32 VPIs out of that range. If you have not yet assigned any VPIs, all values from 0 to 255 are available. Once you start assigning VPIs, however, the assigned VPIs limit the VPIs that remain. (You assign VPIs using the atm pvp or atm pvc command.)

After a particular VPI value is assigned to a shaped VP tunnel, every 32nd VPI value above and below the first one is eliminated—that is, the original value modulo 32. For example, if you assign VPI 94 to a shaped VP tunnel, the following VPI values become unavailable for any purpose: 30, 62, 126, 158, 190, and 222.

To avoid problems, choose a block of 32 consecutive VPI values (for example, 0 to 31 or 101 to 132). The software rejects invalid VPI values.

Installing Multiple Cisco 6160 DSLAMs in an Equipment Rack

You can install multiple Cisco 6160 DSLAMs in a Telco equipment rack. A standard 7-foot equipment rack can house four Cisco 6160 DSLAMs, stacked one on top of another. This configuration maximizes the DSL density within a 7-foot rack. However, if space is available or you are interested in using any multiservice capabilities that the DSLAM might support in the future, we recommend that you install no more than three Cisco 6160 DSLAMs in a 7-foot rack. Leave a space of at least 2.5 rack units (4.375 inches, or 11.1 cm) beneath each DSLAM for future cable management use.

Console Logging

Turn console logging off if you plan to reboot the DSLAM. Turn console logging back on after the system comes up. (Console logging is turned on by default.) Use the global configuration commands no logging console (to turn the feature off) and logging console (to turn it on).

If console logging is on when the system reboots, the large volume of console messages consumes CPU time. As a result, the system comes back up more slowly and line cards might reload repeatedly, causing further delays.

Caveats

Caveats describe unexpected behavior in Cisco IOS software releases. Severity 1 caveats are the most serious caveats; severity 2 caveats are less serious. Severity 3 caveats are moderate caveats, and only select severity 3 caveats are included here.

This section contains only open, closed, and resolved caveats for the current Cisco IOS release.

Caveat numbers and brief descriptions are listed in the following tables. For details about a particular caveat and for information on caveats in previous Cisco IOS releases that also apply to this release, go to Bug Toolkit at:

To access this location, you must have an account on Cisco.com. If you have forgotten or lost your account information, e-mail the Contact Database Administration group at cdbadmin@cisco.com. If you do not have an account on Cisco.com, go to http://www.cisco.com/register and follow the directions to set up an account.

Note If you have an account with Cisco.com, you can use Bug Navigator II to find caveats of any severity for any release. To reach Bug Navigator II, go to Cisco.com and click Login. Then go to Software Center > Cisco IOS Software > Cisco Bugtool Navigator II. Alternatively, you can go to

http://www.cisco.com/cgi-bin/Support/Bugtool/launch_bugtool.pl

This software release is based on Cisco IOS Release 12.2. For information on caveats in Cisco IOS Release 12.2, see Caveats for Cisco IOS Release 12.2, which lists severity 1 and 2 caveats and select severity 3 caveats for Cisco IOS Release 12.2. It is located on Cisco.com and the Documentation CD-ROM.

Open Caveats—Release 12.2(12)DA

Resolved Caveats—Release 12.2(12)DA

Table 4 Open Caveats in Cisco IOS Release 12.2(12)DA
Caveat Number	Description
CSCdy70425	After the CPE trains with the 8xDMT-ISDN line card, the number of DMT check bytes allocated for forward error correction (FEC) on the line card does not match the number of DMT check bytes provisioned. This problem occurs in both interleaved and fast path mode. Workaround: None.
CSCdz05530	On an OC-3 interface, the show interface command "packets output" count does not match the show controller command "cells transmitted" count, but both should be the same. Workaround: None.

Table 5 Caveats Resolved in Cisco IOS Release 12.2(12)DA
Caveat Number	Description
CSCdx60278	Clearing the interface counters on a Cisco 6260 DSLAM now works correctly. Previously, the counters might not have been cleared and could instead show high input and cyclic redundancy check (CRC) errors.
CSCdx92465	The show dsl interface atm command now shows the correct value for the Last Change field for G.SHDSL ports. Previously, if the system clock value was altered after the G.SHDSL port trained, this field might show an erroneous value.
CSCdy21341	Issuing the clear counters command on an OC-3 interface no longer causes SNMP to incorrectly show ifTable counters equal to 0.
CSCdy22386	SNMP now checks to ensure that you specify a valid value for Upstream Checkbytes on a DSL profile. Previously, SNMP allowed you to specify any value for cAdslAturDmtConfInterleaveFecSize (CISCO-ADSL-DMT-LINE-MIB), even though valid values are 0 through 16, in multiples of 2.
CSCdy70396	The 8xDMTISDN line card no longer drops the connection after it trains with a Cisco 826 CPE when the line card's downstream bit rate is less than 5504 kilobits per second (kbps). Previously, this problem caused constant link flapping.

Open Caveats—Release 12.2(10)DA

All of the caveats listed in Table 6 are open in Cisco IOS Release 12.2(10)DA. This table lists only severity 1 and 2 caveats and some severity 3 caveats.

Table 6 Open Caveats in Cisco IOS Release 12.2(10)DA
Caveat Number	Description
CSCdx53819	8xDMT cards with interleaving delay configurations of 2000 microseconds or less can have problems holding the training rate or having less than expected upstream training rates. Workaround: Avoid interleaving delay values of 2000 microseconds and less with 8xDMT cards. For interleaving mode configurations, use a 4000 microsecond delay or better. If lower delays are required, use fast path mode if it is supported by the CPE.
CSCdx57259	The connection between the modem on a 4xDMT line card and the CPE is lost when an NI-2 card redundancy switchover occurs. Workaround: None.
CSCdx67720	When you copy a configuration file from a TFTP server to the startup_config through SNMP, ccCopyState (CISCO-CONFIG-COPY-MIB) stays in the Running state forever. It does not change to the Failed state. The show startup command displays the following output: `%% Non-volatile configuration memory is being accessed, Try again` Workaround: Make sure there is enough space available in NVRAM before copying, using SNMP or CLI.
CSCdx84898	Upgrades from Cisco IOS Release 12.1.(7) DA to newer Cisco IOS software images cause G.SHDSL ports to occasionally drop and retrain. The error is listed as LOSQ (Loss of Signal Quality) due to CRC errors detected or LOS when Loss of Frame Sync is detected. Workaround: Newer versions of G.SHDSL firmware have been adjusted to meet the ratified standards. This may require some fixed-rate loops to not hold train at the current configured rate used with Cisco IOS Release 12.1.(7)DA. In some cases, reducing the configured rate resolves the issue. Random drops might still occur on some ports.

Resolved Caveats—Release 12.2(10)DA

Table 7 Caveats Resolved in Cisco IOS Release 12.2(10)DA
Caveat Number	Description
CSCdp00996	Periodically, the system generates a serial management bus cyclic redundancy check (SMBCRC) error message such as this: `%NI2-5-LC_NOTICE:Slot[15] SMBCRC (1 days, 3 hours, 37 minutes, 6 seconds)` These messages are informational only and do not affect performance.
CSCdu04045	The entry for the atmSoftPVccRetryThreshold feature has an incorrect default value of 0, rather than the default value of 1 that is shown in the ATM soft PVC Management Information Base (MIB). A value of zero indicates that an infinite number of call attempts are required to increment the atmSoftPvcCallFailures object and thus disables alarms for the soft PVC.
CSCdu40049	Adding and deleting a profile from different sessions (for example, in two Telnet sessions, one user is adding while at the same time another is deleting the same profile) has the potential of causing an unexpected system reload.
CSCdu42394	The ceAssetTag cannot be set for 8xDMT and SHDSL line cards.
CSCdv56813	Following a redundancy switchover, the standby card may reload twice before reaching the STANDBY-READY state. Once the standby is in the STANDBY-READY state it will not continue to reload.
CSCdv73591	Some VCs (PVCs/PVPs/Soft PVCs/Soft PVPs) are missing on reload even when they are stored in the startup configuration. This problem occurs if you create VCs by using internal CTT rows that do not appear in the show running-config command but do appear in the show atm connection-traffic-table command.
CSCdw53009	When you configure the ATUC-1-4DMT line card for loopback diagnostic, cells are dropped by the interface.
CSCdw67176	The commands no tag-switching ip and tag-switching ip from the global configuration mode remove the tag-switching atm vp-tunnel 13 vci-range 33-65535 line on the sub interfaces.
CSCdw73531	Not all IMA group/link alarms are shown in the event browser.
CSCdw87272	If you try to enable tag-switching ip, the following message appears: `%VP-tunnel vpi is not free for Tag-switching`.
CSCdw91698	The NI-2 card does not support OAM F5 seg-loopback cells, in the fast path.
CSCdx16449	PNNI fails to establish a connection. The show atm controller atm 0/0 command displays a status of C.
CSCdx19656	Unable to train with 3Com OCR-810. With the 4xDMT line card, the CPE exhibited line errors and failures in training with Release 12.2(7)DA. Trellis encoding is enabled in the DSL profile.
CSCdx34262	When you change the operation of the linecard from ATUC-1-DMT8 to STUC-8-TCPAM, the indexes appear in the incorrect order.
CSCdx43027	The system stops responding indefinitely after you provisioning or unprovision slots.
CSCdx64312	In Cisco IOS Release 12.2(7)DA, the value of the "Microseconds handling network interrupts" is not saved correctly to the NVRAM when configured through the scheduler allocate exec command.
CSCdx65171	The NI-2 card unexpectedly reloads when you try to clear a card mismatch from CLI using the command no slot x, where x is the slot number.
CSCdy02467	Adtran CPEs do not train with a Cisco 6260 DSLAM that is running Cisco IOS Release 12.2(7)DA.

Open Caveats—Release 12.2(7)DA

Resolved Caveats—Release 12.2(7)DA

Table 8 Caveats Resolved in Cisco IOS Release 12.2(7)DA
Caveat Number	Description
CSCdp68075	The input queue field in the output of the show interface atm slot/port occasionally shows a negative number.
CSCds48063	The cAdslAtuc/AturCapCurrRxGain in the CISCO-ADSL-CAP-LINE-MIB returns an incorrect value for short loops (less than 2000 feet).
CSCds51529	For the STUC G.SHDSL line card, all far end (STUR) statistics that appear through the CLI or SNMP are reported as zero.
CSCdt87954	The G.SHDSL line card does not support rate adaption.
CSCdu00802	The ifSpeed object from the ifTable returns an incorrect speed at the ATM layer for a 4xFlexi DMT line card.
CSCdu35160	Packet loss occurs when you police with abr for MCR values greater than 18.
CSCdu48003	The Init event counter toggles between 0 and 4294967295 several times in a minute for a 4xFlexi DMT line card.
CSCdu81936	An ARP packet received by the router that has the router's own interface address but with a different MAC address can overwrite the router's own MAC address in the ARP table, causing that interface to stop sending and receiving traffic. This attack is successful only against interfaces on the Ethernet segment that is local to the attacking host.
CSCdv12425	The error message ERROR: Irrecoverable IDT 252 RCQ last Cell problem detected! appears and is repeated several times. ATM OAM cells are not handled correctly and these error messages finally lead to system reload.
CSCdv30504	Far End LPR Events are not incrementing on the ATUC-4FLEXI-DMT line card when the power is removed from a CPE that supports the dying gasp feature of the DMT standard.
CSCdv38294	VPI/VCI values for provisioned PVC do not match the provisioned values when you select a VCI value of 0 for any non-terminating PVC (that is, a PVC not terminating at atm0/0).
CSCdv80202	The shdsl profile has a different format between Cisco IOS Release 12.1(7)DA and Cisco IOS Release 12.2(5).
CSCdv86663	When you configure an interface bandwidth statement on a Cisco 6260 DSLAM ATM interface, the default bandwidth value for the interface as seen in the show interface atm command may appear in the show running-config output.
CSCdw03128	Cisco 6260 DSLAM SNMP agent returns incorrect ifType for SHDSL interfaces.
CSCdw25440	Using the command show atm vc interface atm slot/port vpi vci where vpi and vci are the VPI and VCI numbers in a SVC configuration can cause the DSLAM to reload. This usually happens when the CPE is connected but the SVC is not yet established.
CSCdw34798	Invalid cells are passed to network port on a valid VC. The 4xDMT line card does not discard cells with HEC errors and stamps each cell going to the DSLAM with a valid HEC. The switch can then pass these corrupt cells out the WAN interface if they appear to have a valid and provisioned VPI and VCI.
CSCdw41743	After 54 days of uptime, the system experienced an unexpected reload immediately preceded by the messages: System reloads with message SYS-2-WATCHDOG process=IMA CORE.
CSCdw47576	An NI-2 DSLAM reloads after a few ALIGN-1-FATAL error messages.
CSCdw65903	An error can occur with management protocol processing. Please use the following URL for further information: http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCdw65903

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