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Cisco IOS Software Releases 12.2 Mainline

Field Notice: CSCin29995 Causes High CPU Utilization Due to Debug Messages For cUDP Packets


Revised September 07, 2005

August 12, 2004


NOTICE:

THIS FIELD NOTICE HAS BEEN ARCHIVED AND IS NO LONGER MAINTAINED OR UPDATED BY CISCO.

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE, WARRANTY OR SUPPORT. USE OF THE INFORMATION ON THIS FIELD NOTICE OR MATERIALS LINKED FROM THIS 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

Comments

7204 - NPE-400

Running 12.2T and decompressing cUDP packets.

7206 - NPE-400

Running 12.2T and decompressing cUDP packets.

7223 - NPE-400

Running 12.2T and decompressing cUDP packets.

7246 - NPE-400

Running 12.2T and decompressing cUDP packets.

7246-VXR - NPE-400

Running 12.2T and decompressing cUDP packets.

8200 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

8800 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

MGX - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

8200 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

MGX8200 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

8800 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

MGX8800 - MGX-RPM-PR-256

Running 12.2T and decompressing cUDP packets.

Problem Description

Routers running IOS releases prior to 12.3 and configured to uncompress cUDP may drop throughput and the command line may appear unresponsive due to high utilization of CPU.

In addition, the console may continuously print the following error on a connected console:

00:29:42: is_rtp_header failed dport xxxx

"xxxx" in the above example error represents the destination UDP port that is logging the errors.

Background

The error logging caused by decompression of cUDP traffic is causing high CPU utilization.

Conditions to see problem require that:

  1. Router operate with 12.2T

  2. Router must uncompress cUDP.

If a router receives cnonTCP, no problems are observed. This anomaly applies only to cUDP decompression.

Problem Symptoms

Router may become unresposive, throughput may be slowed, and/or compressed packets may be discarded.

The following error is logged on the router console:

00:29:42: is_rtp_header failed dport xxxx* 

"xxxx*" represents the destination UDP port.

One such error is logged for each cUDP packet received. The more cUDP packets are received, the more errors are logged the more CPU is consumed servicing the error interrupts.

Note: cUDP packets are properly handled provided the CPU has enough cycles to decompress the packets. The presence of the is_rtp_header errors do not indicate that data is being discarded or corrupted.

Workaround/Solution

Workaround:

Execute the command:

PE1(config)#
logging rate-limit all 1 except 6 

This command limits the rate of error logging for errors below severity 6 and thus reduces utilization of router's CPU by rate limiting debug messages that are logged. The logged error, Jul 28 19:28:15.603: is_rtp_header failed dport xxxx is a debug error.

The user should note that rate limiting log messages does not prevent logging. Unique errors, irrespective of severity, are logged at least once. Multiple exact log messages are suppressed.

Solution:

This anomaly is fixed in Cisco IOS® Release 12.3(1). This release may be downloaded from cisco.com

This anomaly is found in Cisco IOS Release 12.2(13)T3, 12.2(15)T1, 12.2(15)T9 and other IOS releases earlier than 12.3. Other 12.2T releases are also affected.

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

CSCin29995 (registered customers only)

is_rtp_header failed msg observed during shut, no shut of ctrl

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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