Unable to access Edgecore switch(EdgeCOS) via SSH? Follow

Problem description:

If the openSSH version newer then 7.0(Figure-1) on your operation system, then you might be see some error messages and unable to access switch via SSH(Figure-2).

Figure-1: OpenSSH V7.8p1 of Ubuntu OS.

ts@ts-ThinkPad-T430:~$ ssh -V
OpenSSH_7.8p1, OpenSSL 1.0.2g 1 Mar 2016

Enabling SSH server on switch.

Console#ip ssh crypto host-key generate
Console#configure
Console(config)#ip ssh server
Console(config)#
Console#show ip ssh
SSH Enabled - Version 2.0
Negotiation Timeout : 120 seconds; Authentication Retries : 3
Server Key Size : 768 bits

Figure-2: You may see the following three types of error messages.

ts@ts-ThinkPad-T430:~$ ssh admin@192.168.30.254
Unable to negotiate with 192.168.30.254 port 22: no matching key exchange method found.
Their offer: diffie-hellman-group1-sha1
ts@ts-ThinkPad-T430:~$
ts@ts-ThinkPad-T430:~$ ssh admin@192.168.30.254
Unable to negotiate with 192.168.30.254 port 22: no matching host key type found. 
Their offer: ssh-dss
ts@ts-ThinkPad-T430:~$
ts@ts-ThinkPad-T430:~$ ssh admin@192.168.30.254
Unable to negotiate with 192.168.30.254 port 22: no matching cipher found. 
Their offer: aes128-cbc,3des-cbc,blowfish-cbc,aes192-cbc,aes256-cbc,des-cbc@ssh.com,
des-cbc

Solution:

<1> Adding the option for algorithms when you execute the SSH.

ts@ts-ThinkPad-T430:~$ ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 
-oHostKeyAlgorithms=+ssh-dss -c aes128-cbc admin@192.168.30.254

The authenticity of host '192.168.30.254 (192.168.30.254)' can't be established.
DSA key fingerprint is SHA256:MSm7td0VkWmmZHJXuo73ZCrQqZQz7pDFaxF7UANaa7Q.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.30.254' (DSA) to the list of known hosts.
admin@192.168.30.254's password:

***************************************************************

WARNING - MONITORED ACTIONS AND ACCESSES

 

Station's information:


Floor / Row / Rack / Sub-Rack
 / / /
DC power supply:
Power Source A: Floor / Row / Rack / Electrical circuit
 / / /

Number of LP:
Position MUX:
IP LAN:
Note:
***************************************************************

CLI session with the ECS4120-28T is opened.
 To end the CLI session, enter [Exit].

Vty-1#

<2> Creating the “/.ssh/config” file before you execute the SSH.

ts@ts-ThinkPad-T430:~$ vi .ssh/config
ts@ts-ThinkPad-T430:~$ cat .ssh/config
Host *
 KexAlgorithms +diffie-hellman-group1-sha1
 HostKeyAlgorithms +ssh-dss
 Ciphers aes128-cbc

ts@ts-ThinkPad-T430:~$ ssh admin@192.168.30.254
admin@192.168.30.254's password:

***************************************************************

WARNING - MONITORED ACTIONS AND ACCESSES

 

Station's information:


Floor / Row / Rack / Sub-Rack
 / / /
DC power supply:
Power Source A: Floor / Row / Rack / Electrical circuit
 / / /

Number of LP:
Position MUX:
IP LAN:
Note:
***************************************************************

CLI session with the ECS4120-28T is opened.
 To end the CLI session, enter [Exit].

Vty-1#

Reference:
[1]https://www.openssh.com/legacy.html