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Ping issues between service modules and the rest of the network with cross-module etherchannel in Catalyst 6500 Series Switches with Supervisor 720 that runs native Cisco IOS

Core issue

Catalyst 6500 Series Switches with Supervisor Engine 720 and service modules can experience connectivity issues between the service modules and the rest of the network in certain scenarios:

  • Scenario 1 When the Distributed Forwarding Card 3 (DFC3), or any type of DFC3a, DFC3b, DFC3bxl, and cross-module Layer 2 EtherChannels are used

  • Scenario 2 When the cross-module Layer 2 EtherChannels in the Supervisor Engine is used and the fabric connection is in bus (flow-through) mode

The affected service modules are:

  • WS-SVC-FWM-1-K9 Firewall Services Module

  • WS-SVC-IDS2-BUN-K9 Intrusion Detection Service Module 2

  • WS-SVC-IPSEC-1 IPsec VPN Accelerator

  • WS-SVC-MWAM-1 Multi-Processor WAN Application Module

  • WS-SVC-NAM-1 Network Analysis Module 1

  • WS-SVC-NAM-2 Network Analysis Module 2

  • WS-SVC-PSD-1 Persistent Storage Device Module

  • WS-SVC-SSL-1-K9 SSL Module

  • WS-SVC-WLAN-1-K9 Wireless LAN Service Module

Note: The WS-SVC-CMM module is also affected. But, due to its internal architecture, it is fixed through a software change to the CMM module itself that can be tracked in Cisco bug ID CSCsa75660. As a result, the resolution mentioned for this case does not apply to the CMM service module.


Cisco bug ID CSCee10005 addresses this issue.

Issue the fabric switching-mode force bus-mode config command to fix this. This command forces the fabric connection of the service module to bus mode.

Note: This command power-cycles the service modules.

It is also possible to upgrade the software code to Cisco IOS  Software Releases 12.2(17d)SXB07, 12.2(18)SXD05, or 12.2(18)SXE in order to fix this, which can be downloaded from Cisco Downloads.

Note: The fix for MWAM modules is not in the Cisco IOS Software Release 12.2(18)SXD05, 12.2(17d)SXB07, or 12.2(18)SXE images. It is tracked on Cisco bug ID CSCsb50559.

Refer to Configuring a Supervisor Engine 720 for more information.


  • Do not use cross-module EtherChannel.

  • Configure the default gateway on the remote switch for the service module, where applicable.    
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‎06-17-2009 10:16 PM
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