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esxi 6 can't connect ssh

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esxi 6 can't connect ssh

Postby dmburgess » Wed Jul 27, 2016 9:53 pm

I have a server that the OBM is connecting to other vmware ESXI boxes, one box, that happens to be v6 it just comes back as won't connect. I can open a putty window on the same server as the OBM i am running and can open SSH just fine to that server. Just get a message "cannot connect SSH, please check the SSH settings" and thats it.
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Re: esxi 6 can't connect ssh

Postby Support3 » Fri Jul 29, 2016 3:45 pm


We do find this issue is due to ESXi v6 Update 2 is embedded with OpenSSH 7.1.

However, start from OpenSSH 7.0, some of the older cryptographic algorithms have been found weak and are disabled by default. (Reference: It includes "diffie-hellman-group1-sha1" which is the algorithm provided for OBM to access the SSH. Hence, this issue occurred.

We have already submitted the bug report for it.

To workaround with this issue, you can re-enable the disabled "diffie-hellman-group1-sha1" on ESXi by following steps:
1. Login to ESXi console
2. Go to ssh config directory
cd /etc/ssh
3. Backup existing config
cp sshd_config sshd_config.bak
4. Edit config
vi sshd_config
5. Add the following line into file and save
KexAlgorithms +diffie-hellman-group1-sha1
6. Restart SSH service
/etc/init.d/SSH restart

After that, you should be able to create/run the ESXi backup again.
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