With our cisco routers and switches, we have the ability to compute the hash value to ensure the image was not corrupt during the download from the cisco website, and the ultimate uploading to our device. I'm going to demonstrate how we can check the image files.
You will meed the CCO on-line or some other authoritative sources for the computed hash known as a md5 CheckSum.
e.g ( cisco support page for a c3550 switch image that we will use in this demo )
Here's the switch;
Here's the internal flash contents;
The file we will verify, is the iosimage file named c3550-ipservicesk9-mz.122-44.SE6.bin
The cli cmd for this activity "verify" will be used for the md5 checksum comparisons. We will use the /md5 option for computing the md5 checksum.
The last line, provides the computed checksum value that should match the CCO software download checksum. In this case, it does.
So we know the following;
- The image was not corrupt
- or tamper with
Notice how the computed values equals our CCO download page values?
Freelance Network / Security Engineer
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