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I'm having trouble using ssh to access a server that I recently set up with 16.04, but only from a specific computer (my laptop). When I run ssh -vvv -p sshPort user@host, I get this output:

OpenSSH_7.2p2 Ubuntu-4, OpenSSL 1.0.2g-fips  1 Mar 2016
debug1: Reading configuration data /home/user/.ssh/config
debug1: /home/user/.ssh/config line 1: Applying options for *
debug1: /home/user/.ssh/config line 35: Applying options for host
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "host" port xxxx
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to host [xxx.xxx.xxx.xxx] port xxxx.
debug1: Connection established.
debug1: identity file /home/user/.ssh/id_rsa type 1                                                                                                                                        
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_rsa-cert type -1                                                                                                                                  
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_dsa type -1                                                                                                                                       
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_dsa-cert type -1                                                                                                                                  
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_ecdsa type -1                                                                                                                                     
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_ecdsa-cert type -1                                                                                                                                
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_ed25519 type -1                                                                                                                                   
debug1: key_load_public: No such file or directory                                                                                                                                            
debug1: identity file /home/user/.ssh/id_ed25519-cert type -1                                                                                                                              
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4
ssh_exchange_identification: Connection closed by remote host

On the server side, /var/log/auth.log just has the entry:

Apr 28 18:50:49 host sshd[2618]: Did not receive identification string from yyy.yyy.yyy.yyy

So far, I haven't been able to figure out why this is happening, and I'm open to suggestions. A few things I've ruled out:

Not port forwarding/firewall configuration issues: I'm able to log in to this host from a remote VPS, so access from the WAN is working properly. I can also ssh in from another host on the same LAN.

Not an issue with fail2ban/denyhosts: This is a new install that doesn't yet have auto-ban software configured. /etc/hosts.deny and /etc/hosts.allow are both empty. SSH config is the default that ships with 16.04.

Not the SSH agent: I can ssh into other hosts from my laptop with agent forwarding and from there SSH into the host I'm having trouble with.

I did recently install kvm and bridge-utils on the laptop. I've seen some mentions of bridge-utils possibly being an issue here, but I doubt it, since ssh works fine with other hosts.

Any help would be greatly appreciated!

  • 1
    it looks like some filtering on the network. – Jakuje Apr 29 '16 at 10:19
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I've solved this issue. Though I'm still unsure of the root cause, it appears that changing the port forwarded by my router has solved the problem. It's possible that the port I was on was already in use by another forwarding rule, or reserved for use by the router.

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