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Old 10-25-2016, 08:42 AM
bford54 bford54 is offline
Join Date: Sep 2011
Posts: 9
bford54 has 10 reputation points
Default sftp backup - Algorithm negotiation fail

I just setup a new Ubuntu Server 16.04 with OpenSSH to backup our CM and System Platform via SFTP.

I've been able to backup our CMM; announcements, security files, names, translations etc..

When I try to do the System Platform backup I get this error message:

an error occurred while trying to connect to the sftp server (server IP addr).

When I look at the log viewer I see this in the message content:

An error occurred while trying to connect to xxx.xxx.xxx.xxx with s8800:Algorithm negotiation fail

What am I doing wrong or where are my setups wrong?

I was previously backing up to an older Windows XP machine using a third party SFTP software.
I wasn't having any problems there but I just wanted to retire the WinXP machine.

Avaya Aura System platform 5.2.1
w/ Comm Msg Mgr.
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Old 10-28-2016, 02:18 PM
bford54 bford54 is offline
Join Date: Sep 2011
Posts: 9
bford54 has 10 reputation points
Solution Confirmed

After a lot of research, reading and trial and error I've got a solution / answer to my problem.

I check'd my ssh log files for errors and found this error;
"Oct 26 16:50:31 ubuntu-avbkup sshd[2024]: fatal: Unable to negotiate with xxx.xxx.xxx.56 port 55751: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1,diffie-hellman-group-exchange-sha1 [preauth]"

I added the following lines to my sshd_config file;
"KexAlgorithms +diffie-hellman-group1-sha1"
"KexAlgorithms +diffie-hellman-group-exchange-sha1"

I was still getting the "Algorithm negotiation fail" message but I got a different error message in my ssh log file:
"Unable to negotiate with xxx.xxx.xxx.56 port 34976: no matching cipher found. Their offer: aes128-cbc,3des-cbc,blowfish-cbc [preauth]"

I had to add another line to my sshd_config file:
"Ciphers aes128-cbc,3des-cbc,blowfish-cbc"

Now my backup files are being uploaded to my Ubuntu Server via SFTP.

Last edited by bford54; 10-28-2016 at 02:39 PM. Reason: trying to mark solved
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