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macossshportforwarding

SSH shows the wrong IP address when SSH with port forward

My use case is I have to access AWS ec2 instances through a jumpbox.

Here is my SSH config.

Host awsjumpbox
  User sshuser
  HostName jumpboxhostname
  IdentityFile /Users/myusername/.ssh/id_rsa
  LocalForward 8022 10.0.168.43:22

It works when I do SCP command to copy files to the EC2 instance.

myusername % scp -r -i ~/aws/aws-keypair.pem -P 8022 * ec2-user@localhost:testdir
The authenticity of host '[localhost]:8022 ([::1]:8022)' can't be established.
ECDSA key fingerprint is SHA256:rrwr62yjP2cgUTT9SowdlrIwGi4jMMwt5x4Aj6E4Y3Y.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[localhost]:8022' (ECDSA) to the list of known hosts.
/etc/profile.d/lang.sh: line 19: warning: setlocale: LC_CTYPE: cannot change locale (UTF-8): No such file or directory
README.md                                     100% 1064    24.3KB/s   00:00

However, when I executed SSH command. It returns a strange IP address.

myusername % ssh -i ~/aws/aws-keypair.pem -P 8022 ec2-user@localhost      
ssh: connect to host 0.0.31.86 port 22: No route to host

What is the cause of this issue? How do I fix it?

Thank you.

Solution

  • Don't use LocalForward and reverse the flow.

    Use ProxyCommand or ProxyJump. This will allow SSH to open a session to your bastion server transparently.

    E.g. your configuration should be something in the line of

    Host 10.0.168.43
  User root
  ProxyCommand ssh -W %h:%p sshuser@awsjumpbox
  ...

    or

    Host 10.0.168.43
  User root
  ProxyJump sshuser@awsjumpbox
  ...