Cisco Catalyst 2900 XL Series Switches

Field Notice: Continuous Resets of ATM Module in Catalyst 2900XL

June 18, 2001

Products Affected


Top Assembly

Printed Circuit Assembly


HW Rev.

Part Number


Part Number







ATM 155 UTP Module







ATM 155 Multimode Fiber Module







ATM 155 SM Fiber Medium Reach Module







ATM 155 Single Mode Long Reach Module


Problem Description

Some ATM modules for the Catalyst 2900 XL series have been reported as continuously resetting. This problem has been seen with both unshielded twisted-pair (UTP) and fiber cabling. The SONET/SDH framer application-specific integrated circuits (ASIC) on the module does not understand the format coming directly from some add-drop multiplexers (ADM) on a SONET/SDH link and generates a high number of back-to-back spurious interrupts to the CPU. This is due to an incompatibility problem between the SONET/SDH framer chip (TNETA 1500) on the ATM module and some SONET/SDH framer chips on the ADMs. These interrupts prevent the module's CPU from responding to a polling or keepalive message from the switch, which resets the ATM module. This problem is not seen when the ATM module is used in its ideal application as an uplink to a high-speed campus ATM network. Cisco does not recommend using the Catalyst XL ATM modules as a link on a metropolitan-area network or as a link directly connected to a SONET/SDH ring with ADMs.


The Catalyst 2912MF XL and Catalyst 2924M XL Ethernet switches provide slots for the addition of single port ATM modules. Four models of the ATM modules provide a single ATM port with a port rate of 155 Mbps. The models differ in the physical layer cabling.

SONET and SDH are physical layer standards for high-speed transport over both UTP and fiber cabling. SONET is defined by the American National Standards Institute (ANSI). It uses STS-x framing. SDH stands for synchronous digital hierarchy and is defined by the International Telecommunications Union (ITU). It uses STM-x framing.

Problem Symptoms

At a periodic interval, the Cisco IOS® Software on the switch confirms that the ATM module is up and operational by polling the ATM module via a keepalive message. If the ATM module fails to respond to the message, the switch retries the polling message 10 times, with a time interval of 4 seconds between each retry. If the ATM module still fails to respond, the switch resets the ATM module and prints the following messages on the switch's console and other terminal sessions:

esp_slot2:module_hostif shutting down.
3d19h: Module in slot 2 was removed
3d19h: MM: If Index Request rcvd
3d19h: MM: If Index Requestpreparing response
esp_slot2:module_hostif initialization complete.
3d19h: Module in slot 2 is inserted

When the problem is occurring, the show controller sonet command shows that the number of interrupts received from the SONET framer is increasing frequently, as quickly as 30 interrupts per minute. These interrupts are abnormal and indicate an error condition on the ATM link.

The output of the show controller sonet command displays the number of SONET framer interrupts in the Number of Interrupts Received field, which is an accumulating 32-bit counter.

cat29-atm#show controller sonet
Catalyst 2900 XL ATM card Statistics       ==================================== 

PMD Information:
Port Type: OC-3c   Port Rate: 155 Mbps   Port Medium: Single Mode Fiber - MR
Port Status:
Framing mode:
PMD Counts:
Section BIP-8 blocks with errors (B1):            0
Line BIP-8/24 blocks with errors (B2):            0
Path BIP-8 errors (B3):                           0
Multierrored cell-header count                    0
Number of times the link has come up:             1
Number of Intr rcvd:                              3642522
Number of OOF Intr rcvd:                          0
Number of LOF Intr rcvd:                          0

For troubleshooting tips, please refer the Troubleshooting Section below.


Inserting an ATM switch such as a Cisco LS1010 between the ATM module and the ADM shields the framer and resolves the problem. Only a configuration in which the ATM module connects directly to an ADM exhibits this problem.

This problem is not seen when the ATM module is used in its ideal application as an uplink to a high-speed campus ATM network. Cisco does not recommend using the Catalyst XL ATM modules as a link on a metropolitan-area network or as a link directly connected to a SONET/SDH ring.

It is important to note that there is no software workaround or solution for this problem.


If you or your customer experiences a problem with continuous or unexpected resets of the ATM module, please use the following steps to isolate the symptoms and confirm that the resets are in fact due to the high number of spurious SONET framer interrupts.

A hidden command is introduced in IOS 12.1(9) and later releases. This command completely masks the interrupts generated by the SONET/SDH framer chip and helps in isolating the symptoms of the problem. This command should not be used as a workaround for the problem.

Use the following procedure to isolate the symptoms:

  1. Execute the following command in the interface configuration mode to disable the framer interrupts:

    ls-2924mxl-3c#(config) int atm1
    ls-2924mxl-3c#(config-if)# atm framerint disable
  2. Execute the show controller sonet command and ensure the interrupt mask says 0xFF, 0xFF and 0x1F when the interrupts are disabled.

  3. Check if the reset problem goes away. If it does, then this is indeed the framer incompatibility problem.

  4. Execute the no atm framerint disable command to return interrupt processing to its normal state.

Note:?Since the interrupts are disabled, any further errors or link down conditions cannot be sensed by the IOS software. Therefore, although Cisco has found that traffic will pass normally with the interrupts disabled, you should not use this command as a workaround since the switch will not be able to detect legitimate line issues. Please check the Workaround/Solution section for a workaround.

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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