In Cisco IOS there's the `service password-encryption` command to encrypt all passwords in the config file to prevent unauthorized individuals from viewing them. 

quoting from <http://www.cisco.com/c/en/us/td/docs/ios/12_2/security/configuration/guide/fsecur_c/scfpass.html> 

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> Caution The service password-encryption command **does not** provide a high level of network security. If you use this command, you should also take additional network security measures.
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then it's written:

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> Although you cannot recover a lost encrypted password (that is, you cannot get the original password back)
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So what do they mean exactly? It does not protect very much because of weak encryption used or because it only protects users from viewing the password in the config file? 

I'm confused because in the Networking Academy material they say 

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> The service password-encryption command applies weak encryption to all unencrypted passwords. 
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So is it weak because it's easy to crack?