The known host files (/etc/ssh/ssh_known_hosts and $HOME/.ssh/known_hosts) contain the public keys for all hosts with which the client can communicate by using Secure Shell. The GlobalKnownHostsFile keyword specifies an alternate file instead of /etc/ssh/ssh_known_hosts. The UserKnownHostsFile keyword specifies an alternate to $HOME/.ssh/known_hosts.
The StrictHostKeyChecking keyword requires new hosts to be added manually to the known hosts file, and refuses any host whose public key has changed or whose public key is not in the known hosts file. The keyword CheckHostIP enables the IP address for hosts in the known host files to be checked, in case a key has been changed due to DNS spoofing.