Cisco IOS ‘Crypto’ Unrecognized Command?


KB ID 0001246 Dtd 15/10/16


I was working on a Cisco 3750-G last week, and I was in the process of setting up SSH access. When I went to generate the crypto key and enable SSH, It fired an error at me. In fact it wouldn't execute any crypto commands;

Core-SW(config)#crypto ?
% Unrecognized command

 no crypto commands

Now I have seen this before, (but not for a while). You need to be running a K9 version of the code. A quick 'show version' will tell you.

Core-SW#show version
Cisco IOS Software, C3750 Software (C3750-IPSERVICES-M), Version 12.2(25)SEB2, RELEASE SOFTWARE (fc1)


So you can either, just use TELNET to manage the switch, or upgrade it to a K9 version of the code, (in my case c3750-ipserviceslmk9-tar.122-55.SE11). I chose to upgrade.

Upgrade Cisco Catalyst 3750G

First I tried to TFTP in the bin file, but I kept getting a lot of 'O' ('out of sequence' errors,) and the process failed. After discussions with a colleague, he recommended I simply use the archive-download command and use the TAR upgrade file instead.

WARNING: These old G series switches only have a 16MB flash in them, the TAR file is about 13.5MB you will need to delete the boot file and folder from flash to upgrade the IOS, but I suggest you copy the bin file out to TFTP in case theres a drama, and you need top copy it back in, before you continue. (In fact backup the switch config as well to be on the safe side!)

Setup your TFTP server, and download your image (c3750-ipserviceslmk9-tar.122-55.SE11.tar).

Delete the .bin file from the flash on the switch, and any associated folders (Note: to delete a folder, the syntax is different). Obviouly you may have different files and folders.

Core-SW delete flash:/c3750-ipservices-mz.122-25.SEB2.bin
Core-SW delete /force /recursive flash:/c3750-i5-mz.121-19.EA1d

Perform the upgrade;

Core-SW archive download-sw /overwrite tftp://

It can take 10 minutes or so, but when complete, check the boot variable is set to the new image, and then reload the switch (It may restart a couple of times that's OK).

Core-SW(config)#do show boot
BOOT path-list : flash:c3750-ipservicesk9-mz.122-55.SE11/c3750-ipservicesk9-mz.122-55.SE11.bin
Config file : flash:/config.text
Private Config file : flash:/private-config.text
Enable Break : no
Manual Boot : no
HELPER path-list :
Auto upgrade : yes
Core-SW(config)#do reload

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Author: PeteLong

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