Incompatible ssh peer – Why you get it while cPanel migration?


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Server migrations can be troublesome even when you do it from control panel.

One such error when migrating from a cPanel to Plesk server is “Incompatible ssh peer“.

Finding the real reason for migration errors can be tricky. In most cases, this happens due to mismatch in old and new server SSH configuration.

That’s why, at 1 onlyhost, we often get requests from our customers to fix Incompatible SSH peer error in cPanel migration as part of our Server Migration Services.

Today, we’ll see how our Migration Engineers set the SSH settings and solve the migration errors.



Common migration errors in Plesk

Plesk is one of the popular web hosting platforms with almost similar features as cPanel. Also, this can be used in both Windows server and Linux servers.

Moreover, it helps to build and manage multiple sites from a single dashboard. Plesk has lots of features such as run updates, monitor performance, a secure and versatile toolkit for WordPress and much more.

Because of all these factors, many customers often switch to Plesk servers.

However, migrating to Plesk servers often ends up in errors too. This may be due to many reasons like incorrect permissions set for the migrating directories on a source server or due to the misconfiguration of SSH settings.

Now, let’s see how our Migration Specialists fixed the ssh peer error that occurs during the migration of accounts from the cPanel server.


What causes “Incompatible ssh peer” error?

From our experience in managing servers, we’ve seen customers facing problems when migrating accounts from cPanel server to Plesk server. It’s now time to take a closer look on what causes the incompatible ssh peer error.


Misconfiguration of SSH ciphers

Basically, cipher is an algorithm or a set of procedure for performing encryption or decryption of data with SSH protocol. The data transfer depends directly on this Cipher set. By default, most server administrators disable weak algorithms and allow only stronger ones. As a result, there can be mismatch in SSL ciphers in various servers.

Often, the misconfiguration of SSH ciphers result in migration errors.

The exact incompatible ssh peer error will show up as:

Failed to perform action: Fetch data from source cPanel
Cause: Failed to connect to the the source server 'cpanel' (xxx.xx.yy.zz) at 'server IP' by SSH as '': Incompatible ssh peer (no acceptable kex algorithm)
That is a critical error, migration was stopped.

This clearly indicates the incorrect SSH cipher algorithm in use.


How we fixed errors when migrating to Plesk server

Therefore, Migration Engineers solved the error by correcting the SSH ciphers. It involves a series of steps.

1. Initially, we log into the server as a root user.

2. Then, we open the file sshd_config  located in /etc/ssh, and add the following directives.

KexAlgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1

We just make sure to add only the secure SSH ciphers.

3. At last, to make the changes effective in SSH, we restart sshd service

service sshd reload

That fixed the error and migration started working again.


[Having trouble while migrating cPanel to Plesk? We’ll fix it for you.]



In short, Incompatible ssh peer error happens in migration due to wrong SSH ciphers on the servers. Today, we saw how our Migration Engineers correct SSH settings and migrate accounts from cPanel to other servers.

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