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Cisco uBR7200 Series Universal Broadband Routers

Field Notice: FN - 62390 - uBR-MC16c, uBR-MC16s and uBR-MC28c Cards Experience Increased FEC Errors with Some Newer Versions of IOS


May 18, 2006

NOTICE:

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.


Products Affected

Products Affected

UBR10K - UBR10-LCP2-MC16C

UBR10K - UBR10-LCP2-MC16S

UBR10K - UBR10-LCP2-MC28C

7246-VXR - UBR-MC16C

7246-VXR - UBR-MC16S

7246-VXR - UBR-MC28C

Problem Description

An increase of upstream FEC errors may be seen using MC16C, MC16S or MC28C cards running the following Cisco IOS releases: 12.3(17a)BC, 12.3(13a)BC1, 12.3(13a)BC2, 12.3(13a)BC3, 12.3(9a)BC8. Exact degradation depends on plant conditions, CMs and MTAs being used. Although the increase of FEC errors have been up to ten times the norm, they are typically less. Modems do not drop offline in most cases.

Background

Initially, an issue was introduced including CSCei72695 (registered customers only) , where a register setting for a receiver chipset was not programmed properly, causing packet loss with legacy line cards that interoperate with some vendor cable modems. The idea was to quickly correct the hardware CMTS chipset receiver setting in software. Meanwhile, cable modem vendors chose to increase QPSK1 preamble power, which caused a bad side effect on DOCSIS compliant based linecards or MC520S/U cards, where SNR was severely degraded to about 17dB. A software fix was put into place and integrated in 12.3(13a)BC02, 12.3(09a)BC08, and 12.3(16.15)BC. Unfortunately, that fix in CSCei72695 introduced a side effect where FEC errors increased on 16c, 16s and 28c line cards, and thus initiated this field notice with a solution provided below.

Problem Symptoms

The result is dropped packets to the point where bad voice quality is experienced in VOIP calls.

Workaround/Solution

Workaround:

There is a workaround using a manufacturing test command to program the receiver PHY to its previous values. Contact TAC to implement this workaround if the solution below is not an option.

Solution:

Upgrade to 12.3(13a)BC4 or later.

This issue will not be seen in 12.3(9a)BC4.

DDTS

To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.

DDTS

Description

CSCsd84940 (registered customers only)

Increase number of FEC errors on 16c and 28c cards

Cisco IOS Versions Affected

12.3(17a)BC, 12.3(13)BC1, 12.3(13)BC2, 12.3(9a)BC8

How To Upgrade Software

Instructions on how to download Cisco IOS from CCO can be found on the Software Center Downloads (registered customers only) page.

Revision History

Revision

Date

Comment

1.0

18-MAY-2006

Initial Public Release

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

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