Are you getting the following error when trying to ssh to an ancient Sonicwall?
ssh_dispatch_run_fatal: Connection to ip.of.sonic.wall port 22: DH GEX group out of range
Give this a try:
ssh -l admin -o KexAlgorithms=diffie-hellman-group1-sha1 -oHostKeyAlgorithms=+ssh-rsa ip.of.sonic.wall