SSH Error ‘No Matching Exchange Method Found’

Thanks to: https://www.petenetlive.com

Unable to negotiate with x.x.x.x port 22: no matching key exchange found. Their offer diffie-hellman-group1-sha1
Note: You may also see the following error;
No Matching Cipher found
Unable to negotiate with x.x.x.x port 22: no matching cipher found. Their offer: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc

Solution

This is not Apple’s fault, it’s OpenSSH version 7. SHA1 is weak, so support for it has been removed. Which is fine, but all my clients Cisco Firewalls/Routers/Switches are probably all using  RSA/SHA1. So until they re all updated I’m going to need to re-enable SHA1.
Open a terminal windows and execute the following;
sudo nano /etc/ssh/ssh_config
ENTER YOUR PASSWORD
Locate the line ‘ #   MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160′ and remove the Hash/Pound sight from the beginning.
Locate the line ‘ #   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc’ and remove the Hash/Pound sight from the beginning.
Then paste the following on the end;
HostkeyAlgorithms ssh-dss,ssh-rsa
KexAlgorithms +diffie-hellman-group1-sha1
Like so;
 Theres no reason to reboot, it should work straight away.

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