I've seen this error on recent SSH versions, including the OpenSSH used by OS X and others:
Unable to negotiate with 192.168.77.1 port 22: no matching cipher found. Their offer: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
Several people suggest modifying your local ssh client config. However, I'd rather not use 3DES unless I have to. So, I created an alias and put it in .bash_profile:
alias ssho='ssh -c 3des-cbc'
after a quick . ~/.bash_profile
I can ssh with the alias:
Of course, the best fix would be to update IOS on the Cisco gear.