routing information protocol (rip) version 2 provides md5 authentication of encryption keys. the pix firewall only listens in passive mode and/or broadcasts a default route. the pix firewall supports cisco ios software standards, which conform to rfc 1058, rfc 1388, and rfc 2082 of ripv2 with text and keyed md5 authentication. the pix firewall supports one key and key id per interface. while the key has an infinite lifetime, for best security, you should change the key every two weeks or sooner.

    the use of telnet to change the configuration may expose the key and key id on the network.