You can pass the -F option to the ssh command that specifies an alternative per-user configuration file instead of the default ~/.ssh/config file. Unfortunately there is no ignore option. You need to get a little creative and pass the /dev/null as a config file which tells ssh to ignore the default ssh config file named ~/.ssh/config. For example:
ssh -F /dev/null user@server-name
OR some people use none as file:
ssh -F none user@server-name
The global /etc/ssh/ssh_config will be ignored if a configuration file is given on the command line. The default for the per-user configuration file is ~/.ssh/config, and it will be ignored too.
https://www.cyberciti.biz/faq/tell-ssh-to-exclude-ignore-config-file/