Connect (SSH) to the same server, through two different gateways, with different server users

Question

What I would like to achieve is to be able to connect to some target.server from my local machine, without having to type any passwords, with the following commands:

ssh user1@target.server
ssh user2@target.server

Each user above only accepts a connection from a specific IP address, corresponding to respectively gateway1.example and gateway2.example. I have added all necessary SSH keys to the right authorized_keys, so that I can do, without typing passwords:

• ssh gateuser1@gateway1.example from local machine, then ssh user1@target.server from gateway1.
• ssh gateuser2@gateway2.example from local machine, then ssh user2@target.server from gateway2.

Now I think it remains to put the right things in my local ~/.ssh/config. When I add:

Host target.server
    ProxyCommand ssh -o 'ForwardAgent yes' gateuser1@gateway1.example 'ssh-add && nc %h %p'

Then ssh user1@target.server works. But I don't know how to make both user1 and user2 work. I tried:

Host target.server
    User user1
    ProxyCommand ssh -o 'ForwardAgent yes' gateuser1@gateway1.example 'ssh-add && nc %h %p'
Host target.server
    User user2
    ProxyCommand ssh -o 'ForwardAgent yes' gateuser2@gateway2.example 'ssh-add && nc %h %p'

or

Host target.server
    User user1
        ProxyCommand ssh -o 'ForwardAgent yes' gateuser1@gateway1.example 'ssh-add && nc %h %p'
    User user2
        ProxyCommand ssh -o 'ForwardAgent yes' gateuser2@gateway2.example 'ssh-add && nc %h %p'

but it still didn't work for user2: all went through gateway1 and not gateway2.

Thank you very much in advance for your help!

Update: I've been able to make the following commands work:

ssh user1
ssh user2

(without @target.server), using the following configuration:

Host user1
    HostName target.server
    User user1
    ProxyCommand ssh -o 'ForwardAgent yes' gateuser1@gateway1.example 'ssh-add && nc %h %p'
Host user2
    HostName target.server
    User user2
    ProxyCommand ssh -o 'ForwardAgent yes' gateuser2@gateway2.example 'ssh-add && nc %h %p'

This is what I will be using, but I'm still curious to see a solution to the two commands at the beginning of this question.

Answer 1

As you figured out, aliases are a good solution. If you don't want to use them, the Match directive might be another valid option.

Host target.server
    Match User user1
        ProxyCommand ssh -o 'ForwardAgent yes' gateuser1@gateway1.example 'ssh-add && nc %h %p'
    Match User user2
        ProxyCommand ssh -o 'ForwardAgent yes' gateuser2@gateway2.example 'ssh-add && nc %h %p'

From the ssh_config man page:

Match Restricts the following declarations (up to the next Host or Match keyword) to be used only when the conditions following the Match keyword are satisfied.