What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags


View all Tags

Reinstalled Linux host - SSH Custom sensor no longer works

Votes:

0

Obviously the SSH keys changed with the new OS install. I'd like to preserve the data I have in my sensors. I'm using a custom SSH script sensor to read some XML data. The PRTG error is "The negotiation of the encryption algorithm is failed". There are no errors logs on my linux host. sshd_config allows

How can I reset the known SSH host key for this device?

prtg ssh ssh-script-advanced-sensor

Created on Mar 21, 2017 6:06:45 PM



5 Replies

Votes:

0

This has nothing to do with the actual key being wrong, but the security ciphers used not up to date. What distribution are you using? Could you try to enable the compatibility mode in the Linux credential section of the device and check if that works?

Created on Mar 22, 2017 7:32:18 PM by Stephan Linke [Paessler Support]



Votes:

0

I am using a new installation of Raspbian (jessie).

I'm not sure what you mean by "compatibility mode". How can I figure out what specifically is the connection problem?

Here's the output of diff from my new sshd_config and the old sshd_config

root@hostname:/etc/ssh# diff sshd_config ./old/sshd_config 14d13 < HostKey /etc/ssh/ssh_host_ed25519_key 20c19 < ServerKeyBits 1024 --- > ServerKeyBits 768

Is PRTG not capable of handling a host key of larger than 768? I commended the HostKey line from the new file that wasn't in the old file (HostKey /etc/ssh/ssh_host_ed25519_key) and that didn't help.

Created on Mar 23, 2017 2:13:39 PM



Votes:

0

What PRTG version are you currently running? I'm using the latest one and it works just fine with Raspbian...

Created on Mar 23, 2017 2:48:09 PM by Stephan Linke [Paessler Support]



Votes:

0

My version of PRTG was 15.4.21.5215

I updated to 16.1.21.1924 and still had the issue. Upgraded to 17.1.30.1618 and it started working.

Thank you for updating your SSH sensors for the new ciphers.

Created on Mar 23, 2017 6:10:52 PM



Votes:

0

Alright, nice - glad it works now :)

Created on Mar 24, 2017 5:38:27 AM by Stephan Linke [Paessler Support]




Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.