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The "%L2_AGING-SP-2-DEC_EN_FAIL: Failed to initialize Distributed EtherChannel" error message appears in Catalyst 6500 series switches running Cisco IOS software


Core issue

This error message appear due to these reasons:

  • Reason 1 This can indicate that one or more resources that are required for the Distributed EtherChannel (DEC) operation are in use by other modules, for example, a Firewall Services Module (FWSM).

  • Reason 2 Another reason for this message can be due to the usage of Crossbar and Bus mode on the modules in the chassis as shown:

6509_Switch#show fabric switching-mode

Global switching mode is Truncated
dCEF mode is not enforced for system to operate
Fabric module is not  required for system to operate
Modules are allowed to operate in bus mode
Truncated mode is allowed, due to presence of CEF720 module

Module Slot  Switching Mode
  1  Crossbar
  3  Crossbar
  4  Crossbar
  5  Bus
  6  Crossbar
  7  Crossbar
  8  Crossbar
  9  Bus

Basically, with Bus mode, all linecards see all packets, and only accept the ones that they need or are destined for them, whereas in Crossbar mode, packets are sent directly to the specific linecard.

Cisco bug ID CSCse87210 identifies this issue.


Solution for Reason 1 Remove the monitor session reserved for service modules.  In order to do this, issue the no monitor session servicemodule command, and then try to reinitialize the operation. This disables the internal-span required by the FWSM to process multicast traffic, which frees the resources on the SPAN-ASIC in order to allow DEC to work.

Solution for Reason 2 The workaround is to change the mode of the modules to bus mode. In order to force fabric-enabled modules into bus switching mode, use the fabric switching-mode force bus-mode command.

In order to resolve the issue mentioned in this bug, you can upgrade to Cisco IOS  Software Release 12.2(18)SXF7 or later, which can be downloaded from Cisco Downloads.


I am having issues recently after I configured port channel on my cisco 6509E switch running IOS Version 12.2(18)SXF4 using 2 different line card,

Pair one:  is using the WS-SUP720-3B uplink (Bus Mode) while other side is WS-X6724-SFP (Crossbar Mode) (Port #g5/2 to Port #g1/16)
Pair two: is using WS-X6724-SFP (Crossbar Mode) on both sides. (Port #g1/14 to Port #g1/14)

While adding the pair one to the channel group it is working perfectly fine, however when I add the Pair two on the port channel then this error is apperaing on my console "The "%L2_AGING-SP-2-DEC_EN_FAIL: Failed to initialize Distributed EtherChannel" error message appears in Catalyst 6500 series switches running Cisco IOS software". 

As per some of forum advised is to upgrade to the current release IOS, and also disable the monitor session for the FWSM unfortunately we cannot do this as of this moment. What I am trying to do as a work around is to:

Pair one: will use the same line card module WS-X6724-SFP (Crossbar Mode) int both sides: (Port #g1/17 to Port #g1/16)
Pair Two: will be using the same line card module in pair one with different ports (Port #g1/14 to Port #g1/14)

Will this solution resolve our issue? please comment....