Bug ID:

Resolved In:

Symptom:

Conditions:

Workaround:

There are two core triggers of this error;

1. When one or more resources that are required for the Distributed EtherChannel (DEC) operation are in use by other modules, e.g. a Firewall Services Module (FWSM) or

2. When a mixture of both Crossbar and Bus mode are in use in the same chassis as shown:

Catalyst-6509-Switch# show fabric switching-mode [module {slot_number | all]

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

In Bus mode, packets are broadcast to all linecards while in Crossbar mode, packets are unicast directly to the specific linecards.

Workarounds

The workaround for the first scenario above is to remove the monitor session reserved for service modules. In order to do this, issue the no monitor session servicemodule command, and then reinitialize the operation. This disables the internal-span required by the FWSM to process multicast traffic, which in turn frees the resources on the SPAN-ASIC in order to allow DEC to work.

The workaround for the second scenario above 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 IOS command.

Solution:

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This document is independent of the software running on the device.

1. Login to the priviledge EXEC mode on the device via console, SSH or Telnet using a terminal emulator program e.g. putty, microsoft hyperterminal, apple terminal etc.
2. Enable Router# terminal length 0 (this makes the console capture to scroll to the bottom of the screen without having to press the space bar - very useful for long captures)
3. Issue the needed captures and save them as text files e.g.

• Router#show tech
• Router#show log

Miscellaneous

• Terminal Emulator Settings for Console Connections
• Capturing Text Output from Hyperterminal

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Definition

Netflow is a technology invented by Cisco systems which allows routers to categorize related packets into flows based on a 7-tuple of IP source address, IP destination address, source port, destination port, protocol, TOS and interface. This technique has been used to switch traffic and to accelerate the switching operation. Today netflow is mainly used for traffic accounting and analysis.

Flexible NetFlow is a ground-up redesign and re-write of netflow, and allows users to define their own flow keys - so they're no longer limited to the 7-tuple.

Netflow exports data from routers to Netflow collectors using a proprietary netflow export format, in versions 1, 5, 8 and 9. IPFIX is the IETF standard developed from the netflow v9 export format. Netflow v9 and IPFIX are template based export formats which are capable of exporting almost any information from the router.

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Definition

In Cisco IOS, alignment errors occur when the software accesses valid memory locations at invalid address boundaries. This is always a software defect. These errors will be displayed on the console, in the logs and also viewable through the hidden Cisco IOS Router#show alignment EXEC command.

Alignment corrections are very CPU-intensive as such, the CPU cycles of a device experiencing alignment errors will be higher than normal - depending on the frequency of the errors and corrections.

Below is an example of the error and command output:

%ALIGN-3-CORRECT: Alignment correction made at 60EF3763 reading/writing 0x60262474

Router#show alignment
Alignment data for:
RSP Software (RSP-ISV-M), Version 12.1(7), RELEASE SOFTWARE (fc1)
Compiled Fri 18-May-01 11:34 by phanguye

Total Corrections 9, Recorded 3, Reads 9, Writes 0

Initial Initial
Address Count Access Type Traceback
60EF3765 3 32bit read 0x60262474 0x601AC594 0x601AC580
60EF3761 3 32bit read 0x60262478 0x601AC594 0x601AC580
60EF3763 3 32bit read 0x60262478 0x601AC594 0x601AC580

No spurious memory references have been recorded.  

In IEEE 802.3 networks, an error that occurs when the total number of bits of a received frame is not divisible by eight. Alignment errors usually are caused by frame damage due to collisions.

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Definition

TRansparent Interconnection of Lots of Links (TRILL) is a protocol in development within the IETF and IEEE as a potential replacement for the Spanning Tree Protocol.

The 802.1d Spanning Tree Protocol is a simple and elegant way of eliminating loops from a bridged Ethernet network; however its simplicity works against it in highly meshed switching networks.  The TRILL working group within the IETF are investigating the use of a link-state protocol to replace the spanning tree to allow more efficient use of network resources within meshed networks.

The problem and applicability statement for TRILL can be found in RFC5556.

References:

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