Could someone here please help me answer this question: have a 6504E running on 15.5(1)SY5 (latest) and need to know if its KEX algorithms can be updated somehow to a more modern set, currently only supporting diffie-hellman-group-exchange-sha1.
here is the latest information :
You could try the following command (replace <size> with the value you need or use ? to see what is available):
ip ssh dh min size <size>
Came across this document. Hopefully it will point you in the right direction.