View source for Rocky 8.x SSH client Connecting to old network devices with legacy protocols and ciphers

[[Main Page|Home]] > [[Rocky Linux or CentOS]] > [[Rocky Linux 8.x]] > [[Rocky 8.x System Administration|System Administration]] > [[Rocky 8.x SSH client|SSH client]] > [[Rocky 8.x SSH client Connecting to old network devices with legacy protocols and ciphers|Connecting to old network devices with legacy protocols and ciphers]]

If while connecting to a network device (eg TP-Link AP or switch) you get errors similar to '''one among''' below:
<pre>
Unable to negotiate with 192.168.4.11 port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1

Unable to negotiate with 192.168.4.11 port 22: no matching host key type found. Their offer: ssh-dss

Unable to negotiate with 192.168.4.11 port 22: no matching cipher found. Their offer: aes128-cbc,aes192-cbc,aes256-cbc,blowfish-cbc,cast128-cbc,3des-cbc
</pre>
then the issue can be solved by using:
<pre>
    ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 -oHostKeyAlgorithms=+ssh-dss -c aes256-cbc <username>@<fqdn-or-ip>
</pre>
where each of the -o option is specifically written to take care of specific errors listed in above example.  


Refer:
* https://askubuntu.com/questions/836048/ssh-returns-no-matching-host-key-type-found-their-offer-ssh-dss
* https://community.cisco.com/t5/network-management/no-matching-key-exchange-method-found-their-offer-diffie-hellman/td-p/4410107



=Enabling ssh-rsa on modern SSH client=
In case of more modern SSH clients ssh-rsa host key protocol may not be enabled by default.  For connecting to Legacy SSH servers using ssh-rsa we can enable the same by editing '<tt>~/.ssh/config</tt>' with:
<pre>
Host *
    HostKeyAlgorithms +ssh-rsa
    PubkeyAcceptedKeyTypes +ssh-rsa
</pre>

Refer:
* https://askubuntu.com/questions/836048/ssh-returns-no-matching-host-key-type-found-their-offer-ssh-dss


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