Loading and Managing System Images Configuration Guide, Cisco IOS Release 15M&T
MD5 File Validation
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MD5 File Validation

MD5 File Validation

The MD5 File Validation feature provides a Cisco IOS software command you can use to ensure file validation using the Message Digest 5 (MD5) algorithm in the Cisco IOS File System (IFS).

The MD5 File Validation feature allows you to check the integrity of a Cisco IOS software image by comparing its MD5 checksum value against a known MD5 checksum value for the image. MD5 values are now made available on Cisco.com for all Cisco IOS software images for comparison against local system image values.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Restrictions for MD5 File Validation

The MD5 File Validation feature can only be used to check the integrity of a Cisco IOS software image that is stored on a Cisco IOS device. It cannot be used to check the integrity of an image on a remote file system or an image running in memory.

Information About MD5 File Validation

MD5 File Validation Overview

The MD5 File Validation feature provides a mechanism for users to verify that system image files are not corrupted or incomplete. This feature uses the industry-standard MD5 algorithm for improved reliability and security. MD5 file validation computes and displays the MD5 values from the Cisco IOS command-line interface (CLI). Files do not have to be checked on another device.


Note


The MD5 file does not have to be on the router in order to verify the Cisco IOS software image.


How to Validate Files Using the MD5 Algorithm

Verifying an Image

The MD5 File Validation feature allows you to generate the MD5 checksum for the Cisco IOS image stored on your router and compare it to the value posted on Cisco.com to verify that the image on your router is not corrupted.

Perform this task to run the MD5 integrity check after transferring an image file.

Image Information

You can obtain the MD5 value for your system image from the Software Center at Cisco.com. The most convenient way to get this value is to click the name of the file prior to download. For example, if you select the 12.2.2T4 Release for the 3640 Platform with the Enterprise Plus Feature Set, before clicking the Download button, you can click the filename for the image (c3640-js-mz.122-2.T4.bin) and the image information will be displayed.

Image information typically includes the Release, Description, File Size, BSD Checksum, Router Checksum, Date Published, and MD5 value for the image. You should record the MD5 value for the image prior to download. However, if you do not have the MD5 value for a previously downloaded image, you can select the same image on Cisco.com (using the same process you would use to download the image) to get the MD5 value.

SUMMARY STEPS

    1.    enable

    2.    Do one of the following:

    • verify /md5 filesystem : filename
    • verify /md5 filesystem : filename md5-value


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2Do one of the following:
    • verify /md5 filesystem : filename
    • verify /md5 filesystem : filename md5-value


    Example:
    Router# verify /md5 disk1:c7200-js-mz


    Example:
              


    Example:
    Router# verify /md5 disk1:c7200-js-mz 0f369ed9e98756f179d4f29d6e7755d3
     

    Verifies the checksum of a file on a flash memory file system or computes an MD5 signature for a file.

    • In the example, disk1 is specified as the filesystem and c7200-js-mz is specified as the filename.

    or

    Displays a message indicating whether the MD5 values match.

    • In the example, the md5-value is specified as 0f369ed9e98756f179d4f29d6e7755d3.

     

    Troubleshooting Tips

    A mismatch in MD5 values means that either the image is corrupt or the wrong MD5 value was entered.

    Configuration Examples for MD5 File Validation

    Verifying an Image Example

    In the following example, the /md5 keyword is used to display the MD5 value for the image stored in disk1 of the device. The MD5 value shown in the last line can be compared to the value provided on Cisco.com.

    Router# verify /md5 disk1:
     
    Verify filename []? c7200-js-mz
     
    ..................................
    ..................................
    ..................................
    ..................................
    ..................................
    ...............................Done!
    verify /md5 (disk1:c7200-js-mz) = 0f369ed9e98756f179d4f29d6e7755d3
    

    In the following example, the known MD5 value for the image is specified in the verify command, and the system checks the value against the stored value:

    Router# verify /md5 disk1:c7200-js-mz ?
     
      WORD  Expected md5 signature
      <cr>
    router# verify /md5 disk1:c7200-js-mz 0f369ed9e98756f179d4f29d6e7755d3
     
    ..................................
    ..................................
    ..................................
    ..................................
    ..................................
    ...............................Done!
    Verified (disk1:c7200-js-mz) = 0f369ed9e98756f179d4f29d6e7755d3

    Additional References

    The following sections provide references related to the MD5 File Validation feature.

    Related Documents

    Related Topic

    Document Title

    Additional commands for loading, maintaining, and rebooting system images

    Cisco IOS Configuration Fundamentals Command Reference

    Standards

    Standard

    Title

    None

    --

    MIBs

    MIB

    MIBs Link

    • None

    To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

    http:/​/​www.cisco.com/​go/​mibs

    RFCs

    RFC

    Title

    RFC 1321

    MD5 Message-Digest Algorithm

    Technical Assistance

    Description

    Link

    The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

    To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

    Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

    http:/​/​www.cisco.com/​techsupport

    Feature Information for MD5 File Validation

    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

    Table 1 Feature Information for MD5 File Vaildation

    Feature Name

    Releases

    Feature Information

    MD5 File Validation

    12.2(4)T 12.0(22)S

    The MD5 File Validation feature allows you to check the integrity of a Cisco IOS software image by comparing its MD5 checksum value against a known MD5 checksum value for the image.

    The following command was introduced or modified: verify.