Trying to logon to some older network switch management interfaces I came across a failure due to them using older SHA1 key exchanges and key types. Thankfully OpenSSH supports some legacy options to get around this, at least until we get the switches replaced or upgraded.
$ ssh [email protected]
Unable to negotiate with 192.168.10.1 port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1Add the option to use DH-G1-SHA1
$ ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 [email protected]
Unable to negotiate with 192.168.10.1 port 22: no matching host key type found. Their offer: ssh-dssSo now add the ability to use the host key type ssh-dss:
$ ssh -oKexAlgorithms=+diffie-hellman-group1-sha1 -oHostKeyAlgorithms=+ssh-dss [email protected]Now we’re on! References: https://www.openssh.com/legacy.html