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

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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)