While installing hadoop in my local machine , i got following error
ssh -vvv localhost OpenSSH_5.5p1, OpenSSL 1.0.0e-fips 6 Sep 2011 debug1: Reading configura
if you are able to ping and not able to ssh, then it is a firewall. The firewall on 18.4 (not sure about other versions) in on by default and only allow port 8080.
Here how you fix it
https://linuxconfig.org/how-to-enable-disable-firewall-on-ubuntu-18-04-bionic-beaver-linux