OpenSSH and Cisco

The OpenSSH package included in Ubuntu 16.04 presents the following error when connecting to Cisco switches/routers with IOS 12.x:

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

In order to continue connecting via SSH, you must add the following option to the ssh command:

-o KexAlgorithms=diffie-hellman-group1-sha1

The completed ssh command then reads:

ssh -o KexAlgorithms=diffie-hellman-group1-sha1 [hostname/ip address]