Host github
        Hostname        github.com
        User            username
        IdentityFile    ~/.ssh/keys/github

Host site1
        Hostname        domain1.com
        Port            22
        User            username
        IdentityFile    ~/.ssh/keys/domain1

Host site2
        Hostname        123.123.123.123
        Port            22
        User            username
        IdentityFile    ~/.ssh/keys/domain2