If you ssh into servers, you must set up a .ssh/config file. It will allow you to type ssh myd instead of ssh myuser@mydomain.com -i ~/.ssh/mykey.pem -p 1234.

First, simply create the file ~/.ssh/config.

Next, paste in this block and customize it for every ssh shortcut you wish to create:

Host shortcutname
HostName 0.1.2.3
Port 22
User jerzy
ServerAliveInterval 120
IdentityFile ~/.ssh/my_super_secret.pem

Then, you would ssh with:

ssh shortcutname

... and BAM! You're on the server.

You can include this template as many times as you want in .ssh/config, separated by new lines. Every server I ssh into is included in my .ssh/config file.

N.B. Many novice Linux users achieve a similar effect with a shell alias. Shell aliases lack the nuanced flexability of a ssh config file, and you should not use them for ssh'ing.