Recently I wanted to connect to some remote server using different ssh keys. With the right ~/.ssh/config file this is easy and comfortable.
Easy
IdentityFile ~/.ssh/%h/%r/id_rsa IdentityFile ~/.ssh/%h/id_rsa IdentityFile ~/.ssh/id_rsa %h and %r are placeholder for host and remote-user. ssh foo@bar will first check if ~/.ssh/bar/foo/id_rsa exists, next ~/.ssh/bar/id_rsa and finally ~/.ssh/id_rsa.
Comfortable
Host github HostName 123.45.678.90 User myuser IdentityFile ~/.ssh/123.45.678.90/id_rsa Instead of ssh myuser@123.45.678.90 the above config allows you to simply type