Define multiple configurations for the same host using the SSH client configuration file.
I am using 192.0.2.44 server which provides SSH access to host on port 22 and guest on port 23.
The guest operating system is using a different SSH username.
SSH client configuration that defines user depending on the remote port.
Match Host 192.0.2.44 exec "test %p = 23" User milosz Match Host 192.0.2.44 exec "test %p = 22" User ansible Match User ansible IdentityFile ~/.ssh/ansible Match User milosz IdentityFile ~/.ssh/milosz Match LocalUser milosz IdentityAgent /home/milosz/.ssh/_socket
Connect to the host on port 22.
$ ssh 192.0.2.44 -p 22 -vv
OpenSSH_8.1p1 Ubuntu-5, OpenSSL 1.1.1d 10 Sep 2019 debug1: Reading configuration data /home/milosz/.ssh/config debug2: checking match for 'Host 192.0.2.44 exec "test %p = 23"' host 192.0.2.44 originally 192.0.2.44 debug1: Executing command: 'test 22 = 23' debug2: match not found debug2: checking match for 'Host 192.0.2.44 exec "test %p = 22"' host 192.0.2.44 originally 192.0.2.44 debug1: Executing command: 'test 22 = 22' debug2: match found debug2: checking match for 'User ansible' host 192.0.2.44 originally 192.0.2.44 debug2: match found debug2: checking match for 'User milosz' host 192.0.2.44 originally 192.0.2.44 debug2: match not found debug2: checking match for 'LocalUser milosz' host 192.0.2.44 originally 192.0.2.44 debug2: match found debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: Applying options for * debug2: resolve_canonicalize: hostname 192.0.2.44 is address debug2: ssh_connect_direct debug1: Connecting to 192.0.2.44 [192.0.2.44] port 22. debug1: Connection established. [...] debug1: Authenticating to 192.0.2.44:22 as 'ansible' [...] Last login: Sun Mar 1 17:09:46 2020 from 94.78.180.181 ansible@lxd:~$
Connect to the guest on port 23.
$ ssh 192.0.2.44 -p 23 -vv
OpenSSH_8.1p1 Ubuntu-5, OpenSSL 1.1.1d 10 Sep 2019 debug1: Reading configuration data /home/milosz/.ssh/config debug2: checking match for 'Host 192.0.2.44 exec "test %p = 23"' host 192.0.2.44 originally 192.0.2.44 debug1: Executing command: 'test 23 = 23' debug2: match found debug2: checking match for 'Host 192.0.2.44 exec "test %p = 22"' host 192.0.2.44 originally 192.0.2.44 debug1: Executing command: 'test 23 = 22' debug2: match not found debug2: checking match for 'User ansible' host 192.0.2.44 originally 192.0.2.44 debug2: match not found debug2: checking match for 'User milosz' host 192.0.2.44 originally 192.0.2.44 debug2: match found debug2: checking match for 'LocalUser milosz' host 192.0.2.44 originally 192.0.2.44 debug2: match found debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: Applying options for * debug2: resolve_canonicalize: hostname 192.0.2.44 is address debug2: ssh_connect_direct debug1: Connecting to 192.0.2.44 [192.0.2.44] port 23. debug1: Connection established. [...] debug1: Authenticating to 192.0.2.44:23 as 'milosz' [...] Last login: Sun Mar 1 17:10:06 2020 from 172.16.32.1 milosz@gitlab:~$
This is very cool!
Additional information
Inspect ssh_config manual page lo learn that you can use keywords like %h (remote hostname), %p (remote port), %r (remote username), %u (local username) and many more.