Cisco 12000 Series Routers

IFS-3-FS_STRUCT_ERROR: Data does not match expected internal representation

Document ID: 26100

Updated: Jan 15, 2008



This document explains the cause of the IFS-3-FS_STRUCT_ERROR: Data does not match expected internal representation error message appearing on a redundant Gigabit Route Processor (GRP) configured for hardware backup, and how to correct the underlying problem. The message can appear on the console or in the system logs.

Before You Begin


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There are no specific prerequisites for this document.

Components Used

The redundant GRP feature discussed in this document is available on Cisco 12000 Series Routers running Cisco IOS® Software Release 11.2(15)GS2 or later.

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.


The GRP redundant processor feature allows you to install two Gigabit Route Processors in a Cisco 12000 Series Internet Router. One GRP functions as the primary processor. The primary GRP supports all normal GRP operation. The other GRP functions as the secondary processor. The secondary GRP monitors the primary and takes over normal GRP operations if it detects a failure in the primary GRP.

The GRP redundant processor feature is not a hot standby system wherein the secondary GRP duplicates the state of the primary. The benefit of having the secondary GRP monitor the primary, rather than duplicate the primary, is that a failure is unlikely to affect both processors. The tradeoff is that network services will be disrupted while the secondary GRP takes over and the router recovers. The recovery happens faster, however, than if the router performed a cold restart.

The redundancy can be configured either for software error protection or for hardware backup, each with its own installation and configuration requirements.

When configured for hardware backup, running different software versions on the redundant GRPs can create issues related to the data/file structures of the two GRPs. Specifically, different Cisco IOS software versions may deal with data in different ways and in different formats. When one Cisco IOS software image attempts to read the data structures produced by a different Cisco IOS software image, the actual structure may differ from the expected structure, which will then cause an error message to be generated:

%IFS-3-FS_STRUCT_ERROR: Data does not match expected internal representation

This message may appear when a user attempts to list the files which are in the secondary filesystem, either through Simple Network Management Protocol (SNMP) or through the command line interface (CLI), and indicates that the redundant GRP software release levels are mismatched.


Verifying the Software Versions

At the command line, enter the show redundancy all command:

GRP Slot  0:  IOS 12.0 redundancy v4  date 2000-07-18
GRP Slot  7:  IOS 12.0 redundancy v5  date 2002-04-21
Auto synch: startup-config

Note the different Cisco IOS software versions evident in the command output.


Update the software loaded on your redundant GRPs to the same software release level; this log message should stop appearing.

To install a new version of Cisco IOS software on either or both of the redundant GRPs, refer to the following documents:

Related Information

Updated: Jan 15, 2008
Document ID: 26100