macOS – no matching key exchange method found. Their offer: diffie-hellman-group1-sha1

TOPICS:Cisco diffie helman el capitan IOS mac osx macOS opens seirra sha ssh

Posted By: Alfred Tong February 26, 2017

Problem

Are you getting this error message when connecting to a SSH Server from your MACOS?

Unable to negotiate with x.x.x.x port 22: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1

Solution

Since the upgrade of El Capitan (10.11) to Sierra (10.12), MAC OS has upgraded their OpenSSH version from 6.9 to 7.2. This change deprecated a number of algorithms by default. This included diffie-hellman-group1-sha1 which is used on most Cisco routers, firewalls and switches.

In order to enable legacy support, perform the following.

Edit or create a new file
```
vi ~/.ssh/config
```

Put this entry in the file

KexAlgorithms diffie-hellman-group1-sha1