applies to:

uname -a
Linux debian 3.16.0-4-686-pae #1 SMP Debian 3.16.39-1+deb8u2 (2017-03-07) i686 GNU/Linux
ssh -V
OpenSSH_6.7p1 Debian-5+deb8u3, OpenSSL 1.0.1t  3 May 2016

ssh -v user@172.20.0.25
/etc/ssh/ssh_config: line 20: Bad configuration option: clientaliveinterval
/etc/ssh/ssh_config: line 21: Bad configuration option: clientalivecountmax
/etc/ssh/ssh_config: terminating, 2 bad configuration options

vim /etc/ssh/sshd_config; # you will have to open up the client-ssh config file and comment out

Host *
# ClientAliveInterval 20 <- this line
# ClientAliveCountMax 5 <- and this line

:wq; # write-save, quit

# then try again
ssh -v user@172.20.0.25; # should work now
admin