If you feel this is a substantial risk in your network, you can use neighbor authentication to protect against it. The Cisco router neighbor authentication takes place with every routing update, so there is some overhead to this. Plain text authentication sends a plain text key with each message. This is vulnerable to snooping. MD5 authentication performs an MD5 hash using a shared secret key, which is less vulnerable to snooping.
Key chains allow a rotating series of keys to be used to decrease the likelihood of compromise.
Since the lifetime of each key is time-sensitive, NTP protocol generally needs to be enabled before using key chains. The table contains links to key parts of the Cisco documentation, in case you wish to look further into this. Y isis password command See also the domain password command. See also the ip rip authentication key-chain command. In response to a suggestion from some readers, I've posted Acrobat PDF versions of all the articles, as well as a ZIP archive containing the index file and all the PDF files.