DB connection error while connecting through unix commands

When I login to the unix db machine and run the command to connect to oracle database

sqlplus db_login_id/db_login_pa开发者_运维问答ssword.

I get error:

ORA-12545: Connect failed because target host or object does not exist

However I can connect to the server using TOAD...so the target definitely exists. What should be my troubleshooting checklist

1) ping the host, 2) check DNS settings, 3) check that the username doesn't need a fully qualified domain name (e.g. kaudshik@whatever.com vs kaudshik)